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Distribution of Gulf of Mexico Sturgeon (Acipenser oxyrinchus desotoi) in relation to environmental parameters and the d...

University of Florida Institutional Repository

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DISTRIBUTION OF GULF OF MEXICO STURGEON ( Acipenser oxyrinchus desotoi ) IN RELATION TO ENVIRONMENTAL PARAMETERS AND THE DISTRIBUTION OF BENTHIC INVERTEBRATES IN THE SUWANNEE RIVER ESTUARY, FLORIDA By JULIANNE E. HARRIS A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2003

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Copyright 2003 by Julianne E. Harris

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To my parents.

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ACKNOWLEDGMENTS I thank my advisor, Dr. Daryl Parkyn, for his help and support. I am very thankful for the opportunity to complete this project with his guidance. I also thank the other members of my committee, cochair Dr. William Lindberg, and members Drs. Debra Murie and Edward Phlips, for their input and advice during all stages of this thesis. In addition, I thank Dr. Kenneth Portier and Mr. Gary Warren for statistical advice and Mr. Roger Portell, Mr. John Slapcinsky and Ms. Sandra Farrington for help with invertebrate identification. Special thanks go to everyone who provided field assistance for this project, including Carla Beals, Mark Butler, Doug Colle, Jaclyn Debicella, Jason Hale, Jamie Holloway, Aaron Hunt Branch, Stephen Larsen, Doug Marcinek, Troy Thompson, and Paul Rebaut. Funding for this project was provided by the Sturgeon Conservation Initiative Grant (DJM and DCP), administered by the Florida Marine Research Institute, St. Petersburg, Florida, and the University of Florida. I am grateful for the love and support of my family and friends. Their continued affection and patience have helped me to complete this project. I especially thank my parents, Edward and Kathleen Pereles, and Ronald and Joan Harris, for their support and motivation. I also thank my brother, David, and my sisters, Jennifer and Jessica, for reminding me what is really important and for making me laugh. I also express my appreciation to Patrick for his constant love, patience, and understanding. iv

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TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................................................................................. iv LIST OF TABLES............................................................................................................. vi LIST OF FIGURES ........................................................................................................... ix ABSTRACT...................................................................................................................... xii CHAPTER 1 INTRODUCTION........................................................................................................1 2 MATERIALS AND METHODS ...............................................................................10 Distribution of Relocated Gulf of Mexico Sturgeon ..................................................10 Distribution of Benthic Invertebrates and Sediment Types........................................13 Benthic Invertebrate and Sediment Laboratory Analysis...........................................14 Relocations of Gulf Sturgeon in Relation to Environmental Parameters and Benthic Invertebrate Distribution ..........................................................................16 3 RESULTS...................................................................................................................25 Distribution of Relocated Gulf Sturgeon....................................................................25 Distribution of Benthic Invertebrates and Sediment Types........................................27 Relocations of Gulf Sturgeon in Relation to Environmental Parameters and Benthic Invertebrate Distribution ..........................................................................28 Environmental Parameters...................................................................................28 Invertebrate Distribution .....................................................................................30 Environmental Parameters and Benthic Invertebrate Distribution......................32 4 DISCUSSION.............................................................................................................93 LIST OF REFERENCES.................................................................................................103 BIOGRAPHICAL SKETCH ...........................................................................................110 v

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LIST OF TABLES Table page 1 Sex, size, and sexual maturity at the time of capture for each Gulf sturgeon surgically implanted with an ultrasonic-tag.............................................................20 2 Dates of tracking surveys of Gulf sturgeon in the Suwannee River estuary, Florida, and other locations along the central Gulf coast of Florida........................21 3 Duration of residency in the Suwannee River estuary by each ultrasonic-tagged Gulf sturgeon during the study period from November 2001 through May 2002...36 4 Mean and first standard deviation of each sediment size type collected from 28 benthic core location sites in the Suwannee River estuary, Florida.........................37 5 Density in abundance and biomass of all invertebrates, excluding polychaetes, collected from benthic core sites in the Suwannee River estuary, Florida...............38 6 Comparisons between the core and petite ponar grab methods for the collection of invertebrates in the Suwannee River estuary, Florida........................................39 7 Spearman Rank Correlations (between relocation positions of Gulf sturgeon in the fall of 2001 and environmental parameters collected from the Suwannee River estuary, Florida...............................................................................................40 8 Spearman Rank Correlations (between relocation positions of Gulf sturgeon in the spring of 2002 and environmental parameters collected from the Suwannee River estuary, Florida.............................................................................41 9 Cluster number and percentage of each sediment size type at each of the 28 benthic core sites collected in the Suwannee River estuary, Florida.......................42 10 Area within each sediment cluster compared to the frequency of relocations of Gulf sturgeon within that cluster..............................................................................43 11 Spearman Rank Correlations (between relocation positions of Gulf sturgeon in the fall of 2001 and the abundance and biomass of all invertebrate genera (excluding polychaetes) collected in the Suwannee River estuary, Florida.............44 vi

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12 Spearman Rank Correlations (between relocation positions of Gulf sturgeon in the spring of 2002 and the abundance and biomass of all invertebrate genera (excluding polychaetes) collected in the Suwannee River estuary, Florida.............45 13 Cluster number and total invertebrate biomass (excluding polychaetes) at each benthic core site collected from the Suwannee River estuary, Florida,...................46 14 Area within each total invertebrate biomass cluster compared to the frequency of relocations of Gulf sturgeon within that cluster.......................................................47 15 Cluster number and numerical abundance of major prey resources: amphipods, brachiopods, and brittle stars, at each of the 28 benthic core sites collected in the Suwannee River estuary, Florida........................................................................48 16 Area within each prey abundance cluster compared to the frequency of relocations of Gulf sturgeon within that cluster.......................................................49 17 Cluster number and total biomass of main prey resources: amphipods, brachiopods, and brittle stars, at each of the 28 benthic core sites collected from the Suwannee River estuary, Florida...............................................................50 18 Area within each prey biomass cluster compared to the frequency of relocations of Gulf sturgeon within that cluster..........................................................................51 19 Cluster number and abundance of brachiopods at each of the 28 benthic core sites collected in the Suwannee River estuary, Florida............................................52 20 Area within each brachiopod abundance cluster compared to the frequency of relocations of Gulf sturgeon within that cluster.......................................................53 21 Cluster number and biomass of brachiopods at each of the 28 benthic core sites collected in the Suwannee River estuary, Florida....................................................54 22 Area within each brachiopod biomass cluster compared to the frequency of relocations of Gulf sturgeon within that cluster.......................................................55 23 Results of canonical correspondence analysis for benthic invertebrate genera collected from 28 core sites in the Suwannee River estuary, Florida......................56 24 Intraset correlations between the environmental variables examined and the first three axes in the canonical correspondence analysis using invertebrate genera collected from 28 core sites in the Suwannee River estuary, Florida...........57 25 Final scores by genera from the canonical correspondence analysis.......................58 26 Results of canonical correspondence analysis for benthic invertebrate families collected from 28 core sites in the Suwannee River estuary, Florida......................59 vii

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27 Intraset correlations between the environmental variables examined and the three axes in the canonical correspondence analysis using invertebrate families collected from 28 core sites in the Suwannee River estuary, Florida......................60 28 Final scores by family from the canonical correspondence analysis.......................61 viii

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LIST OF FIGURES Figure page 1 Study area on the Gulf coast of Florida delineated into tracking areas....................22 2 Benthic core sites in the Suwannee River estuary, Florida, depicted within the boundary of the Main Suwannee tracking area........................................................23 3 Core collection diagram...........................................................................................24 4 Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee River estuary, Florida, during the fall of 2001 and the spring of 2002....................62 5 Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee River estuary, Florida, during the fall of 2001 ........................................................63 6 Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee River estuary, Florida, during the spring of 2002....................................................64 7 Patterns of relocations of Gulf sturgeon in the Suwannee River estuary during the fall of 2001 and the spring of 2002 calculated as utilization distributions.........65 8 Relocation positions for two individual tagged Gulf sturgeon, Fish F and Fish M, in the Suwannee River estuary, Florida........................................................................66 9 Relocation positions for Fish G in the Suwannee River estuary, Florida................67 10 Relocation positions for Fish H in the Suwannee River estuary, Florida................68 11 Relocation positions for Fish C in the Suwannee River estuary, Florida................69 12 Relocation positions for Fish Q in the Suwannee River estuary, Florida................70 13 Patterns of relocations of tagged Gulf sturgeon in the Suwannee River estuary during the fall of 2001 calculated as utilization distributions......................71 14 Patterns of relocations of Gulf sturgeon in the Suwannee River estuary during the spring of 2002 calculated as utilization distributions.........................................72 15 Total relative abundance of all invertebrate taxa by phylum, except annelids, from all 28 cores collected in the Suwannee River estuary, Florida........................73 ix

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16 Total relative biomass of all invertebrate taxa by phylum, except annelids, from all 28 cores collected in the Suwannee River estuary, Florida........................74 17 Temperature and salinity at relocation positions of Gulf sturgeon in the Suwannee River estuary...........................................................................................75 18 Percent sediment size type clustered by benthic core site........................................76 19 Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the fall of 2001 and spring of 2002 in relation to sediment type from 28 core sites in the Suwannee River estuary...........................................................................................77 20 Total biomass of all invertebrates (excluding polychaetes) clustered by benthic core site....................................................................................................................78 21 Relocations of all Gulf sturgeon in the Suwannee River estuary, Florida, in the fall of 2001 and spring of 2002 in relation to total invertebrate biomass from 28 core sites in the Suwannee River estuary............................................................79 22 Numerical abundance of the Gulf sturgeons main prey resources: amphipods, brachiopods, and brittle stars, clustered by benthic core site...............80 23 Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the fall of 2001 and the spring of 2002 in relation to the abundance of their main prey resources collected from 28 core sites in the Suwannee River estuary...81 24 Total biomass of the Gulf sturgeons main prey resources as seen in stomach contents: amphipods, brachiopods, and brittle stars, clustered by benthic core site............................................................................................................................82 25 Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the fall of 2001 and spring of 2002 in relation to the total biomass of their main prey resources collected from 28 core sites in the Suwannee River estuary............83 26 Abundance of brachiopods clustered by benthic core site.......................................84 27 Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the fall of 2001 and spring of 2002 in relation to brachiopod abundance collected from 28 core sites in the Suwannee River estuary...................................................85 28 The distribution of ultrasonic-tagged Gulf sturgeon in relation to the distribution of brachiopods (abundance/m 2 ) in the Suwannee River estuary..........86 29 Biomass of brachiopods clustered by benthic core site ...........................................87 30 Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the fall of 2001 and the spring of 2002 in relation to brachiopod biomass collected from 28 core sites in the Suwannee River estuary...................................................88 x

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31 The distribution of ultrasonic-tagged Gulf sturgeon in relation to the distribution of brachiopods (biomass/m 2 ) in the Suwannee River estuary..............89 32 Biplot of the canonical correspondence analysis of invertebrate genera and relocations of Gulf sturgeon by season, by environmental parameters (CCA axes 1 and 2, represented) .......................................................................................90 33 Biplot of the canonical correspondence analysis of invertebrate genera and relocations of Gulf sturgeon by season, by environmental parameters (CCA axes 1 and 3, represented) .......................................................................................91 34 Biplot of the canonical correspondence analysis of invertebrate families and relocations of Gulf sturgeon by season, by environmental parameters (CCA axes 1 and 2, represented) .......................................................................................92 35 Locations of two non-tagged Gulf sturgeon observed jumping in the Offshore tracking area on March 8, 2002..............................................................................102 xi

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science DISTRIBUTION OF GULF OF MEXICO STURGEON (Acipenser oxyrinchus desotoi) IN RELATION TO ENVIRONMENTAL PARAMETERS AND THE DISTRIBUTION OF BENTHIC INVERTEBRATES IN THE SUWANNEE RIVER ESTUARY, FLORIDA By Julianne E. Harris August 2003 Chair: Daryl C. Parkyn Cochair: William J. Lindberg Major Department: Fisheries and Aquatic Sciences Gulf of Mexico sturgeon, Acipenser oxyrinchus desotoi, inhabit the Suwannee River, Florida, from late spring through early fall before migrating into the Suwannee River estuary and nearshore Gulf of Mexico. Despite this long river residence, it has been suggested that Gulf sturgeon forage almost exclusively while in marine and estuarine environments. The primary goal of the present study was to examine the distribution of ultrasonic-tagged Gulf sturgeon in the Suwannee River estuary, Florida, in relation to water quality parameters (salinity, temperature, and dissolved oxygen), sediment type, and the distribution of benthic invertebrates, especially the distribution of the Gulf sturgeons main prey resources: amphipods, brachiopods, and brittle stars. Ultrasonic-tagged Gulf sturgeon were tracked on emigration from the Suwannee River in the fall of 2001 until they returned to the river in the spring of 2002. Water quality parameters were recorded at each relocation position. Patterns of use of the Suwannee xii

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River estuary by the relocated Gulf sturgeon were calculated as utilization distributions. Sediment and invertebrates were collected from 28 locations in the Suwannee River estuary. Twelve of the eighteen tagged Gulf sturgeon were relocated at least once in the Suwannee River estuary from November 7 through December 19, 2001, and then not again until March 14 through April 17, 2002, for a total of 39 relocations. Relocations of Gulf sturgeon were associated with areas comprised mostly of sand and containing high abundances of their main prey resources: amphipods, brachiopods, and brittle stars, especially brachiopods, the dominant organism observed in stomach contents. Canonical correspondence analysis and examination of temperature and salinity at relocation positions of Gulf sturgeon during the fall of 2001 and spring of 2002 suggested differential use of the Suwannee River estuary during the two different seasons. In the fall of 2001, relocations of Gulf sturgeon were more associated with offshore areas characterized by higher salinity and lower temperature than were relocations in the spring 2002. The association between Gulf sturgeon and their main prey resources indicates that areas within the Suwannee River estuary may be critical foraging habitat for Gulf sturgeon and that any degradation of the benthos in these areas may pose future risks for the recovery of this threatened species. xiii

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CHAPTER 1 INTRODUCTION The Gulf sturgeon, Acipenser oxyrinchus desotoi, is an anadromous fish that seasonally inhabits rivers and coastal areas in the Gulf of Mexico. Historically, Gulf sturgeon spawned in rivers from Louisiana to Charlotte Harbor, Florida (Fox et al. 2000); however, habitat changes, pollution, and overfishing have severely reduced populations and restricted their distribution (Carr et al. 1996). At present, Gulf sturgeon are found only in systems from east of the Mississippi River to the Suwannee River, Florida (Fox et al. 2000). The Suwannee River in northwest Florida is thought to have the largest and most viable population (Foster and Clugston 1997) with an estimated population size of 5,500 sub-adult and adult fish (Pine et al. 2001). The commercial fishery of Gulf sturgeon began in Tampa Bay in 1886. However, the fishery was abandoned four years later because insufficient numbers of fish were caught. In 1896, the fishery resumed near the mouth of the Suwannee River (Huff 1975). The Apalachicola River also supported a Gulf sturgeon fishery, which effectively ended in 1970 when only five fish were caught (Wooley and Crateau 1985). While it is known that commercial fisheries for Gulf sturgeon existed in other rivers along the Gulf of Mexico, documentation of the history of these fisheries is scant. In Florida, Gulf sturgeon sustained substantial commercial and limited sport fisheries (Fox et al. 2000); however, population declines led to the closure of all fisheries in 1984 in the state (Carr et al. 1996). In 1991, the Gulf sturgeon was listed as a threatened species under the Endangered Species Act of 1973 (Carr et al. 1996). To increase populations, the United 1

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2 States Fish and Wildlife Service (USFWS) and the Gulf States Marine Fisheries Commission (GSMFC) worked together to complete a Recovery/Fishery Management Plan for the Gulf sturgeon calling for more information to be collected on natural history and habitat requirements for the species (Fox et al. 2000). One critical component of the Gulf Sturgeon Recovery/Fishery Management Plan was the identification of critical estuarine and marine habitats for the Gulf of Mexico sturgeon (USFWS et al. 1995). In August of 2001, a landmark court decision mandated that the Federal Government define and protect essential fish habitat (EFH) for Gulf of Mexico sturgeon. Areas of critical habitat were to be defined by February of 2003 (USFW and NMFS). Ecological research on Gulf sturgeon has focused mostly on river use and has concentrated on river systems in Florida, especially the Suwannee River because the Suwannee is thought to have the largest and most viable population of Gulf sturgeon (Pine et al. 2001). Gulf sturgeon migrate into the Suwannee River between late February and early July when surface temperatures in the river have risen to an average of 22.1 C (Foster and Clugston 1997). Chapman and Carr (1995) observed Gulf sturgeon entering the river at slightly lower temperatures (peak temperature at entrance averaged 17.2 C) and that this immigration occurred with incoming tides when temperature differences between the Gulf of Mexico and the Suwannee River were at a minimum (about 1-2 C difference). The observed difference between the two studies, with respect to river temperature during migration, may be a result of differences in depth where temperature measurements were collected in the water column. By late July, fish begin to congregate in the river near springs where they will stay for the summer (Foster and Clugston 1997). Gulf sturgeon spawn in the upper areas of the river in March and April (Sulak and

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3 Clugston 1998, 1999). Non-spawning fish also enter the river (Huff 1975, Chapman and Carr 1995) for reasons that are not yet fully understood. It has been hypothesized that Gulf sturgeon reside in the Suwannee River from late spring to mid-fall because the river waters are cool, due to numerous springs (Chapman and Carr 1995, Carr et al. 1996, Foster and Clugston 1997). Gulf sturgeon remain in the Suwannee River until late August to early December (Foster and Clugston 1997), when they migrate down river and enter the Gulf of Mexico (Smith and Clugston 1997). It has been suggested that this migration may be initiated by a decrease in temperature (Wooley and Crateau 1985, Chapman and Carr 1995, Foster and Clugston 1997). The role of temperature in the migration from riverine to estuarine environments has been observed in another Gulf of Mexico species, the Gulf striped bass, Morone saxatilis. Like Gulf sturgeon, Gulf striped bass have been extirpated from many of the coastal river systems where populations previously existed. They originally ranged from Lake Pontchartrain, Louisiana, to the Suwannee River, Florida (Wooley and Crateau 1983). Gulf striped bass remain in rivers through the summer, taking advantage of the cool refuge provided by the springs. A mark and re-capture study has shown that significant weight loss occurred while the fish were in the river, suggesting that metabolic needs were higher, feeding was reduced, or both (Wooley and Crateau 1983). Temperature has been suggested to play an important role in the timing of migration of other anadromous species including sockeye salmon, Oncorhychus nerka (Hodgson and Quinn 2002), and brown trout, Salmo trutta (Jonsson and Jonsson 2002). Patterns of use of estuarine and nearshore marine habitat by Gulf sturgeon in the Choctawhatchee Bay system suggested that most sturgeon remained in the nearshore

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4 waters of the Choctawatchee Bay on substrates that were predominantly composed of sand and in depths of usually 2-4 m (Fox et al. 2002). Fox et al. (2002) located three tagged fish in fully marine waters of the Gulf of Mexico and hypothesized that nine of the twenty tagged fish migrated from the Choctawatchee Bay into the Gulf for a period of at least six weeks. Less research has been conducted on estuarine and marine habitat use by Gulf sturgeon in the Suwannee River system. Sulak and Clugston (1999) tracked six tagged sturgeon continuously for periods up to three days in the Suwannee River estuary and found that the tagged fish remained in nearshore waters, 5-10 m deep, from October through mid-December. In another study, tagged sturgeon were observed to reside outside the Suwannee River, in the Suwannee Sound, for 2-4 weeks before leaving the area (Carr et al. 1996). Current thought is that Gulf sturgeon forage almost exclusively in estuarine and Gulf waters (Huff 1975, Wooley and Crateau 1985, Mason and Clugston 1993, Gu et al. 2001). While some Gulf sturgeon stomachs contained prey when they entered the Suwannee River from the adjacent estuary, they were empty in higher areas of the river (Mason and Clugston 1993). This suggests that the fish did not eat while in the river. Also, Gulf sturgeon had higher length to weight ratios after they spent the summer in the Suwannee River than just before they entered the Suwannee River in the spring, which may have been caused by fasting, but may also have been a result of a change in reproductive status (Huff 1975). Similarly, a mark and recapture study in the Apalachicola River, Florida, found that individual Gulf sturgeon lost about 4-15 of their body weights while in the river (Wooley and Crateau 1985). In addition, the average and range of carbon-13 ratios for adult and sub-adult Gulf of Mexico sturgeon

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5 were more consistent with the signatures of biota and sediment organic matter from the Gulf of Mexico than with signatures of benthic organisms collected in the Suwannee River (Gu et al. 2001). These studies support the idea that sturgeon feed almost exclusively in estuarine/marine waters and little in rivers. However, Gulf sturgeon in Choctawatchee Bay were typically found in areas with low invertebrate densities (Fox et al. 2002). The authors hypothesized that Gulf sturgeon in this system may forage primarily on specific invertebrates that could not be collected by their sampling gear, such as the ghost shrimp, Lepidophthalmus louisianensis, and the snapping shrimp, Leptalpheus forcepts (Fox et al. 2002). Similar studies on foraging behavior and the use of estuarine and marine environments have been conducted on other Acipenser species. The white sturgeon, A. transmontanus, is anadromous in some river systems. Many anadromous white sturgeon live and feed in estuaries (McKechnie and Fenner 1971, Muir et al. 1988), especially near shallow water areas where benthic prey resources are plentiful (McKechnie and Fenner 1971). In the Columbia River system, white sturgeon stomach contents revealed that juveniles primarily consumed the amphipod, Corophium salmonis, while larger individuals preyed more heavily upon marine fish, especially the northern anchovy, Engraulis mordax (Muir et al. 1988, McCabe et al. 1993). In contrast, white sturgeon in San Pablo and Suisun Bays, California, consumed mostly clams (McKechnie and Fenner 1971). Because of the wide variety of prey resources consumed by white sturgeon, it is probable that this species is an opportunistic forager. The relationship between specific prey densities and juvenile white sturgeon densities in the Columbia River was poor. Authors suggested that white sturgeon may migrate to the estuary to forage, or may

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6 simply be feeding very efficiently in the river (McCabe et al. 1993). More studies need to be conducted to determine where these sturgeon are specifically foraging. Lake sturgeon, A. fulvescens, is a potadromous species inhabiting lake and river environments. Lake sturgeon in the Moose River drainage, Ontario, appeared to be generalists, feeding upon macroinvertbrates, especially the burrowing mayfly, Hexagenia sp. (Chiasson et al. 1997, Beamish et al. 1998). In Lake Winnebago, Wisconsin, lake sturgeon were observed to forage primarily upon baetid nymphs (O. Ephemeroptera) and dipteran larvae (Kempinger 1996). Juvenile lake sturgeon were observed to be in highest densities in areas where known prey species were found in only moderate density (Chiasson et al. 1997, Rusak and Mosindy 1997). However, lake sturgeon were found more often in areas with clay substrates, as were the benthic invertebrates that they consumed (Chiasson et al. 1997, Beamish et al. 1998). The green sturgeon, A. medirostris, is an anadromous species of the North Pacific. Little is known about the life history of this species (Scott and Crossman 1973, Erickson et al. 2002); however, it is thought that green sturgeon forage in the estuarine mouths of large rivers (Scott and Crossman 1973, Erickson et al. 2002). One account of the food habits of seventy-five individuals from Kyuoquat Sound, British Columbia, found that the sturgeon had been eating sand lance, Ammodytes hexapterus (Hart 1973), a fish that buries in the sand. The movements of shortnose sturgeon, A. brevirostrum, are complex and differ depending upon river system and latitude. More northern populations (e.g., Maine and New Brunswick) spend most of their time in brackish or marine waters. Adults leave the estuaries from June until August to forage in the rivers when the rivers temperatures are

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7 at their highest. More centrally-distributed shortnose sturgeon (e.g., Massachusetts to Delaware) use marine waters the least, entering for only a very short period of time. Populations in the more southern portion of the sturgeons distribution (e.g., North Carolina and Georgia) enter marine waters during the winter and forage either in or just upstream of the saltwater/freshwater interface. Water temperature differences are hypothesized to cause this change in behavior (Kynard 1997). In many systems, shortnose sturgeon appear to have very specific areas of the river and estuary where they spawn, forage, overwinter, and rest. Shortnose sturgeon migrate to and from these areas over the course of the year (Bain 1997, Hall et al. 1991, Buckely and Kynard 1985, Hastings et al. 1987). Juvenile shortnose sturgeon in the Saint John River Estuary, New Brunswick, eat primarily insects and crustaceans, while adults eat mostly molluscs (Dadswell 1979). Shortnose sturgeon in the Hudson River Estuary were observed to eat soft-bodied invertebrates, including amphipods, chironomids, and isopods (Haley 1998). The closest relatives to the Gulf sturgeon are the Atlantic sturgeon, A. o. oxyrinchus, and the European sturgeon, A. sturio (Artyukhin and Vecsei 1999). These two species spend most of the year in estuarine and marine environments and usually enter freshwater only to spawn. Spawning occurs for European sturgeon in May and June (Lepage and Rochard 1995). Atlantic sturgeon spawn following the latitudinal pattern of February and March in more southern rivers, April and May in centrally located rivers, and May through July in Canadian rivers (Smith and Clugston 1997). Before migrating to the ocean, juvenile European sturgeon congregate in prey-rich regions of the Gironde River Estuary, France, possibly to feed on polychaetes, their main prey resource (Brosse et al. 2000, Taverny et al. 2002). Populations of Atlantic sturgeon

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8 in New York, Massachusetts, and South Carolina appear to spend most of the year in an estuary or the Atlantic ocean and may only move up river to spawn (Dovel and Berggren 1983, Kieffer and Kynard 1993, Collins et al. 2000). In the Hudson River Estuary, juvenile Atlantic sturgeon were observed to forage on polychaetes, isopods, and amphipods (Haley 1998). Observations of feeding habits off the coast of New Jersey determined that Atlantic sturgeon ate during the spring and fall, however, a larger proportion of empty stomachs were observed in the spring. Atlantic sturgeon in this system primarily foraged on polychaetes followed by isopods, decapods, and amphipods. Authors noted that there were differences in the relative importance of different prey types between the two seasons (Johnson et al. 1997). Despite available food resources (Mason 1991), adult Gulf sturgeon appear to forage little in the Suwannee River. Mason and Clugston (1993) found that stomach contents from adult sturgeon entering the Suwannee River contained nearshore coastal shelf organisms including: lancelets, Branchiostoma caribaeum, brachiopods, unidentified pelagic shrimps, polychaetes, molluscs, starfish, and sea cucumbers (Mason and Clugston 1993). Carr et al. (1996) examined 157 adult Suwannee River Gulf sturgeon and found that 32% of stomachs contained exclusively brachiopods and ghost shrimp and 11% contained lancelets, echinoderms, and bivalves. From 2000-2002, stomach contents collected from Gulf sturgeon entering the Suwannee River from the estuary contained: 69% brachiopods, 24% amphipods, 2% brittle stars and 5% other organisms such as isopods, sea cucumbers, shrimp, and polychaetes (Murie and Parkyn 2002).

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9 The primary goal of this study was to examine the distribution of the Gulf of Mexico sturgeon in relation to the distribution of their prey resources in the Suwannee River estuary and adjacent nearshore regions of the Gulf of Mexico. The specific objectives were: 1) to track sonically-tagged Gulf sturgeon in the Suwannee River estuary and nearshore Gulf of Mexico; 2) to determine the distributions of benthic invertebrate species in the Suwannee River estuary; and 3) to examine the relationship between relocations of Gulf sturgeon, specific prey resource densities, and environmental parameters in the Suwannee River estuary.

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CHAPTER 2 MATERIALS AND METHODS Distribution of Relocated Gulf of Mexico Sturgeon Eighteen adult Gulf of Mexico sturgeon, six females and twelve males, were caught using gill nets at the mouth of the Suwannee River (East Pass) during their upstream migration between February and April, 2001, as part of a study addressing the effects of broodstock collection on mortality of net captured sturgeon (Parkyn et al. unpublished data). Each Gulf sturgeon was surgically implanted with a high power ultrasonic tag (Chp 87-L, Sonotronics Tucson, AZ). Size and reproductive status of each ultrasonic tagged Gulf sturgeon is presented in Table 1. Tags operated at a frequency of 73 to 78 kHz, which is optimal for use in both freshwater and marine environments (Sonotronics, personal communication) and could be heard from distances of 1-3 km, depending upon salinity, tag strength, and bathymetry. Each tag had its own unique pulse pattern facilitating the identification of individual fish relocated during the study period. Tracking for the present study began as tagged Gulf sturgeon left the Suwannee River in the fall of 2001 and continued until the fish re-entered the Suwannee River in the spring of 2002. The majority of tracking took place within 7 km of the coastline outside the Suwannee River; however, tracking surveys were also conducted farther offshore and in estuarine areas outside Cedar Key, Waccasassa River, and Crystal River, Florida (Figure 1). Tracking surveys were conducted on 48 different days during this period: five in November, six in December, ten in January, six in February, ten in March, and eleven in April (Table 2). Individual fish were located by tracking along transects oriented 10

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11 parallel to the coastline and typically less than 1.85 km (1 nautical mile) apart to ensure that all tagged sturgeon between transects would be located. Gulf sturgeon were located along transects using an omni-directional ultrasonic hydrophone (DH3, Sonotronics, Tucson, AZ) and receiver (USR-96, Sonotronics, Tucson, AZ), which receives sonic pulses from the ultrasonic tags earlier implanted inside the sturgeon. Once a signal was received with the omni-directional hydrophone, a directional hydrophone (dh-1, Sonotronics, Tucson, AZ), Global Positioning Satellite receiver (GPS)(Garmin GPS 12, Olathe, KS), and compass (Silva Ranger, Livingston, Great Britain) were used to triangulate the fishs position. Temperature, dissolved oxygen, and salinity were measured 10 cm above the bottom using a YSI 85 meter (Yellow Springs Instrument Corp., Yellow Springs, AZ). To determine if relocations of Gulf sturgeon were uniform, random, or aggregated in their distribution, a Clark and Evans nearest neighbor index of aggregation test was used (Krebs 1989). Area within the Main Suwannee tracking area (MSTA) (Figure 1) and distances between relocation positions of sturgeon were calculated using ArcView 3.2 (ESRI 1999). Points representing all individual relocations of Gulf sturgeon in the MSTA of the estuary were included in the analysis to increase sample size; however, if a sturgeon was followed or otherwise relocated more than once during the same day, only the first relocation for the day was included to standardize for effort. The first relocation of a given fish on a given day was used in this and all subsequent analyses in this study. Patterns of use of the Suwannee River estuary by the tagged Gulf sturgeon were examined using a kernel method. Kernel methods produce non-parametric estimations of an animals utilization distribution (UD), which is defined as the distribution of an

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12 animals positions in a plane (Worton 1989). Utilization distributions of 50%, 80%, and 95% (the smaller the percentage, the more highly used the area is) were calculated using the Animal Movement SA Version 2.04 extension in ArcView 3.2 (ESRI 1999). Utilization distributions were calculated using a fixed kernel size and a least-squares cross-validation choice for the smoothing factor. This method has been shown to estimate UDs with accuracy, even when sample sizes are low (Worton 1989, Seaman et al. 1999). This kernel method was applied to relocation positions of Gulf sturgeon during the entire study period, as well as for relocations in the fall of 2001 and those in the spring of 2002 separately, for comparison. In the present study, UDs were calculated for the purpose of examining and displaying use of the Suwannee River estuary by the tagged Gulf sturgeon during the tracking period, not to estimate home range. Patterns of use were not examined by minimum convex polygons because they could not be properly constructed using the sample sizes obtained in this study. To test the hypothesis that the number of male sturgeon and female sturgeon relocated during the fall of 2001 and spring of 2002 were equal, a Fishers exact test was used (SAS 2000). To test the hypothesis that the interval of time spent in the Suwannee River estuary by males and females during the spring of 2002 was similar, a Wilcoxon Rank Sum test was used (Hollander and Wolfe 1999, SAS 2000). To test the hypotheses that bottom temperature, salinity, and dissolved oxygen, at sites where sturgeon were relocated during the fall of 2001 and the spring of 2002 were similar, Student and Satterthwaite t-tests were used (SAS 2000). Satterthwaite t-tests (SAS 2000, Reed 2003) were used when variances between groups differed (Folded F

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13 test, P < 0.01), but groups did not deviate greatly from normality (Shapiro-Wilk, P > 0.01) (SAS 2000). Distribution of Benthic Invertebrates and Sediment Types Benthic cores were collected from 28 locations, between April 22 and May 9, 2002, to survey the distribution of benthic invertebrates in the Suwannee River estuary (Figure 2). The general area selected for benthic invertebrate examination was the Main Suwannee tracking area (MSTA) (Figure 1). Twenty-three sample sites were evenly spaced within the MSTA, one sample site was intended to be part of the evenly spaced grid, but had to be moved slightly because it was out of the water, and four sample sites were specifically placed within the MSTA near locations with higher numbers of relocations of Gulf sturgeon (Figure 2). Divers collected cores using SCUBA when sites were more than 1.5 m in depth and snorkel when sites were shallower. Each core was made of a 15.24 cm piece of 10.16 cm diameter PVC pipe, fitted with two lids. The core, therefore, had a surface area of 81cm 2 and a volume of 1234 cm 3 At each site, ten cores were collected, two at the center and two from each of four locations ~30.5 m from the center, determined by swimming bearings of 50, 140, 230, and 320 degrees from the central location. These specific bearings were chosen because they were parallel to the coastline (Figure 3). Cores collected from the same site and bearing were pooled as a means of increasing the volume of material sampled and considered one sample in subsequent examinations. Temperature, dissolved oxygen, and salinity were measured 10 cm above the bottom, as described previously for water quality parameters collected at relocations positions of Gulf sturgeon. Depth at mean low water at each site was determined from the NOAA navigation chart for the region (Chart 11408, 1998). Distance from each central core

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14 location to the center of the closest entrance to the Suwannee River was measured using ArcView 3.2 (ESRI 1999). The basemap of the Suwannee River estuary used for this project was FLSHR (1-8): Florida Shoreline (Florida Department of Environmental Protection). In addition to benthic cores, three benthic sub-samples were collected using a petite ponar grab (400mm 2 ) from six core locations to allow comparisons between the two collection methods in terms of relative invertebrate abundance and absolute number of genera collected. The six core sites randomly selected were 3X, 5Y, 7Y, 7Z, 8Y and 9Z (Figure 2). Both cores and petite ponar grabs were immediately frozen until they could be processed. Benthic Invertebrate and Sediment Laboratory Analysis Sediment from each sample was described using a modified Wentworth scale. To examine sediment characteristics, one quarter of each core was run through a series of five sieves: 4 mm, 2 mm, 0.85 mm, 0.25 mm, and 0.125 mm. The percent sediment captured within each sieve was estimated visually. Sediment groups were named according to particle size: Oyster Shell (4mm); Small Shell (2mm); Coarse Sand (0.85mm); Medium Sand (0.25mm); Fine Sand (0.125mm); and Silt (below 0.125mm). Fine Sand and Silt were combined for analysis and called Very Fine Sand and Coarse Sand and Medium Sand were merged and called Sand to reduce the number of sediment variables used for analysis. Oyster Shell and Small Shell were not combined because they were composed of shell from different organisms and could represent very different habitat types. Sites with high percentages of Oyster Shell were usually part of or near a living oyster bar composed of the eastern oyster, Crassostrea virginica, whereas sites with high percentages of Small Shell were not always in areas near oyster bars. All

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15 remaining sediment was run through a 0.85 mm sieve. All invertebrates retained by the 0.85 mm sieve and coarser were collected for enumeration and identification. All invertebrates collected from a sample were examined immediately after the sieving process. Invertebrates were sorted, counted, weighed, and then fixed in 5% phosphate-buffered formalin and saved for later identification. In cases where more than ten specimens of the same species were found within a sample, groups were sometimes formed according to size and subsamples of individuals within each size group were weighed. Total weight for all specimens of each species was later estimated based upon the known weights of the subsamples. Individuals of some species were also measured for length and width. All invertebrates were later identified to the lowest taxonomic level possible using reference keys (Richardson 1905, Thomas 1962, Williams 1964, Menzies and Frankenberg 1966, Bousfield 1973, Watling 1979, Heard 1982, Williams 1984, Abele and Kim 1986, Hendler et al. 1995, LeCroy 2000). Polychaetes were not identified because incompatibility with the collection technique prevented preservation of features needed for taxonomic identification. Some specimens of each species were permanently stored in 70% ethanol as a reference collection. Identification of reference specimens were verified by specialists from the University of Florida Museum of Natural History and by comparison with voucher identified specimens from the invertebrate collection at the Florida Marine Research Institute. The reference collection for the present study is archived at the Department of Fisheries and Aquatic Sciences, University of Florida. To test the hypothesis that the relative abundances of specific invertebrate groups collected by the core and petite ponar grab methods, at each of the six sites, were similar, Fishers exact tests were used (Zar 1999, SAS 2000). In addition, to test the hypothesis

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16 that the absolute number of genera collected by the two methods at each site was similar, a Friedman distribution-free randomized complete block design test was used (Hollander and Wolfe 1999). Relocations of Gulf Sturgeon in Relation to Environmental Parameters and Benthic Invertebrate Distribution To examine correlations between the frequency of relocations of Gulf sturgeon in the fall of 2001 and those in the spring of 2002, with environmental parameters, and with the abundance and biomass of specific invertebrate genera, Spearman Rank Correlation tests were used (Hollander and Wolfe 1999, SAS 2000). Each relocation position of a Gulf sturgeon was assigned to the nearest benthic core site for these analyses. Benthic core sites were clustered using the Wards minimum variance method (PC-ORD 4, MjM Software Design 1999) according to: sediment size type; total biomass of all invertebrates (excluding polychaetes); abundance and biomass of the Gulf of Mexico sturgeons main prey resources in the Suwannee River estuary as observed in stomach contents: amphipods, brachiopods, and brittle stars (Murie and Parkyn 2002); and abundance and biomass of brachiopods, the dominant food resource found in the stomachs of Gulf sturgeon in the Suwannee River system. Wards is a hierarchical clustering method that describes the distance between any two objects as the squared sum of the distances of each object from the clusters mean. In each step of the process the cluster that is formed is the one that results in the smallest increase in the sum of squares (Tinsley and Brown 2000). Prey abundances were log 10 (x+1) transformed to reduce the variation between the three prey groups and brachiopod abundance was log 10 (x+1) transformed to reduce the effect of very high abundances. It was unnecessary to transform data for any other cluster analyses. Core sites were then projected into an

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17 equal area projection and interpolated to fill the MSTA using the Create Theissen Polygons extension in ArcView 3.2 (ESRI 1999). In Theissen polygon interpolation, also known as nearest neighbor interpolation, adjacent areas not sampled are assigned the value of the closest sample (Bolstad 2002). Interpolated core sites were then grouped according to their cluster number, and area within each cluster was calculated. To determine if the frequency of relocations of Gulf sturgeon within each cluster, compared to the area within each cluster, was similar, Fishers exact tests were used. The purpose of these Fishers exact tests was to determine if relocations of sturgeon were significantly distributed within the MSTA according to any of the clustered variables: sediment size type, total invertebrate biomass, abundance and biomass of main prey resources, and abundance and biomass of brachiopods. To further examine the distribution of Gulf sturgeon in relation to the abundance and biomass of brachiopods, brachiopod abundance/m 2 and biomass/m 2 were interpolated using an inverse distance weighting method and displayed with all relocation positions of Gulf sturgeon during the fall of 2001 and the spring of 2002 using ArcView 3.2 (ESRI 1999). The inverse distance weighting method estimates the values of unknown locations using the values and distances of neighboring points. The farther away a neighboring point is, the less weight its value will have on defining the value of the unknown location (Bolstad 2002). Canonical correspondence analyses (CCA)(PC-ORD 4) was used to examine the distribution of the relocations of Gulf sturgeon in the fall of 2001 and spring of 2002 and benthic invertebrates, in relation to tested environmental parameters (Ter Braak 1986, Palmer 1993). CCA is a robust weighted-averaging method that directly ordinates community data in a fashion consistent with tested environmental variables, therefore,

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18 variation in the distribution of the invertebrates can be explained in terms of the environmental parameters examined in the study. CCA provides a direct multivariate analysis, such that gradients within the environmental variables are regressed into the ordination procedure during each step of the iteration process (Ter Braak 1986, Palmer 1993, Rakocinski et al. 1997). CCA was conducted on invertebrate abundances at both the genera and the family levels to determine if outcomes between the levels would be similar (Warwick 1988, Somerfield and Clarke 1995). Genera or families observed at less than three of the 28 sample sites were removed from analysis to reduce the effects of rare taxa. Taxa abundances were transformed by log 10 (y+1) for the analysis to reduce the effect of absolute abundances. Environmental parameters included four sediment measures: Oyster Shell, Small Shell, Sand, and Very Fine Sand; as well as three environmental parameters: Depth, Distance from the closest mouth of the Suwannee River (DFRM), and Dissolved Oxygen. Because Gulf sturgeon were not relocated at the specific date or time when environmental parameters were measured for the CCA, temperature and salinity were excluded from these analyses. Temperature and salinity were observed to vary greatly depending upon the specific time and date of collection and therefore may cause bias to the results. Percent data (sediment parameters) were arcsin transformed (Zar 1999) and directly measured data (all other environmental parameters) were transformed by log 10 (x+1) to reduce kurtosis (Griffith et al. 2001, Marchetti and Moyle 2001, Ysebaert and Herman 2002, Griffith et al. 2003). Intraset correlations are the correlations between the environmental variables and the ordination axes (Ter Braak 1986). Using intraset correlations is recommended because, in the CCA process, invertebrates are ordinated according to the tested environmental variables. Thus, the

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19 reader is able to see the direction and magnitude of the relationship between the axes created and the specific environmental variables tested (Palmer 1993, McCune and Mefford 1999). However, CCA procedures can inflate intraset correlation values because the tested environmental parameters themselves constrain the calculation of the ordination axes. Therefore, it is suggested that the signs and relative magnitudes of the intraset values be used to examine the relative importance of each environmental variable in structuring the invertebrate community, not as independent measures of the strength of the relationships between the specific environmental variables and the invertebrate community (McCune and Mefford 1999). For descriptive purposes in this study, intraset values greater than 0.399 were considered more highly correlated than those below 0.399. This criterion was not intended to reflect statistical significance and all intraset values are presented for the reader to examine.

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20 Table 1. Sex, size, and sexual maturity at the time of capture for each Gulf sturgeon surgically implanted with an ultrasonic tag. Gulf sturgeon were captured in gill nets at the mouth of the Suwannee River from February through April of 2001. Fish Identifier Sex Total Length (cm) Fork Length (cm) Weight (kg) Sexually Mature A Male 1496 1332 19.25 Yes B Male 1613 1429 29.25 Yes C Male 1345 1217 16.50 Yes D Male 1279 1137 15.25 Yes E Male 1450 1295 17.25 Yes F Male 1540 1370 22.25 Yes G Male 1375 1224 16.25 Yes H Male 1484 1333 22.50 Yes I Male 1476 1340 19.75 Yes J Male 1406 1256 18.75 Yes K Male 1622 1415 28.75 Yes L Male 1473 1319 20.00 Yes M Female 2010 1790 53.25 No N Female 1922 1776 42.25 Yes O Female 1869 1717 53.25 Yes P Female 1798 1595 46.25 Yes Q Female 1846 1688 52.75 Yes R Female 1768 1575 41.75 Yes

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21 Table 2. Dates of tracking surveys of Gulf sturgeon in the Suwannee River estuary, Florida, and other locations along the central Gulf coast of Florida. Month Day Year Tracking Area November 7 2001 Main Suwannee November 11 2001 Main Suwannee November 18 2001 Main Suwannee November 20 2001 Main Suwannee and Lower Suwannee November 28 2001 Main Suwannee December 2 2001 Main Suwannee December 8 2001 Main Suwannee December 10 2001 Main Suwannee December 15 2001 Main Suwannee December 19 2001 Main Suwannee and Upper Suwannee December 20 2001 Main Suwannee and Upper Suwannee January 5 2002 Main Suwannee and Offshore January 9 2002 Main Suwannee January 10 2002 Offshore January 11 2002 Offshore January 17 2002 Offshore January 26 2002 Lower Suwannee and Cedar Key January 27 2002 Cedar Key January 28 2002 Waccasassa Bay January 29 2002 Waccasassa Bay January 31 2002 Crystal River Estuary February 8 2002 Offshore February 9 2002 Main Suwannee February 12 2002 Main Suwannee February 15 2002 Main Suwannee and Lower Suwannee February 24 2002 Main Suwannee February 28 2002 Main Suwannee and Lower Suwannee March 1 2002 Main Suwannee March 7 2002 Main Suwannee and Offshore March 8 2002 Offshore March 9 2002 Main Suwannee March 12 2002 Main Suwannee and Offshore March 13 2002 Main Suwannee March 15 2002 Main Suwannee March 16 2002 Main Suwannee and Lower Suwannee March 17 2002 Main Suwannee March 18 2002 Main Suwannee and Upper Suwannee April 1 2002 Main Suwannee April 2 2002 Main Suwannee April 10 2002 Main Suwannee April 13 2002 Main Suwannee April 14 2002 Main Suwannee April 15 2002 Main Suwannee April 16 2002 Main Suwannee April 17 2002 Main Suwannee April 19 2002 Lower Suwannee April 23 2002 Main Suwannee April 26 2002 Main Suwannee and Lower Suwannee

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22 A C BDE F G Figure 1. Study area on the Gulf coast of Florida delineated into tracking areas. Tracking Areas: AMain Suwannee, BLower Suwannee, CUpper Suwannee, DCedar Key, EOffshore, FWaccasassa Bay, GCrystal River estuary.

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23 2X 2Y 3X 3Y 2Z S1 4X 3Z 4Y 5X 4Z 5Y 6X 5Z 6Y 7X S2 6Z 8X 7Y 8Y S3 S4 7Z 9X 8Z 9Y 9Z Figure 2. Benthic core sites (filled circles) in the Suwannee River estuary, Florida, depicted within the boundary of the Main Suwannee tracking area. Labels nearest to each benthic core site represent the specific site identifier. S-sites were specifically chosen because high numbers of sturgeon were relocated near those locations. All cores were collected from the Suwannee River estuary, Florida, from April 22 through May 9, 2002.

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24 320 230 140 50 Figure 3. Core collection diagram: Cores were collected from the center location, illustrated on the map, and then four satellite locations 30.5 m from the central location, by swimming 50, 140, 230, and 320 from the center. All cores were collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002.

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CHAPTER 3 RESULTS Distribution of Relocated Gulf Sturgeon Thirteen of the eighteen Gulf of Mexico sturgeon tagged in the spring of 2001 were relocated in the Suwannee River estuary from November 2001, through May 2002, for a total of 39 relocations in the 48 days of tracking. Tagged sturgeon were relocated in the estuary in the fall from November 7, 2001, through December 19, 2001, and then again in the spring from March 14, 2002, through April 17, 2002. However, no Gulf sturgeon were relocated during the months of January or February 2002. Eight of 18 tagged-sturgeon, seven males and one female, were relocated in the estuary during the fall of 2001 for durations of one to six days ( Xs1 d 2.1 2.1 days) (Table 3). During the spring of 2002, 10 of 18 tagged-sturgeon, five males and five females, were relocated in the estuary for durations of one to 31 days (8.3 10.8 days) (Table 3). No significant difference was detected between the number of males found during the fall and spring, and the number of females found during the fall and spring (Fishers exact test, n = 2, P = 0.15). In addition, no significant difference was detected between the relocation interval for males and females during the spring of 2002 (Wilcoxon t-approximation, two sample, two-sided test, n = 10, W = 23, P = 0.40). All relocations of tagged sturgeon were made in the Main Suwannee tracking area (MSTA), except one, which was made in the Lower Suwannee tracking area (Figures 4-6). Within the MSTA, relocations of Gulf sturgeon were significantly aggregated or clumped in their distribution (Clark and Evans nearest neighbor index of aggregation test, 25

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26 n = 38, Z = -3.78, P <0.001). Patterns of relocations of Gulf sturgeon, calculated as utilization distributions (UD) and including all relocations (n = 39), in the Suwannee River estuary during the fall of 2001 and the spring of 2002 are illustrated in Figure 7. The most highly used area, the 50% UD, was situated adjacent to Alligator Pass, one of the three mouths of the Suwannee River. North of West Pass was also a well used area. Much of the MSTA appears to be used by Gulf sturgeon during the fall and spring relocation periods (Figure 7). Five of the eighteen tagged Gulf sturgeon were relocated in the MSTA during both the fall of 2001 and the spring of 2002 (Table 3). However, the movements of these five sturgeon within the MSTA during the fall of 2001 and the spring of 2002 appear different. Two of the five Gulf sturgeon, Fish F and Fish M, were relocated in one general area in the fall and in a different area in the spring (Figure 8). In contrast, Fish G was relocated outside Alligator Pass in both the fall and the spring (Figure 9). Fish H was relocated only once during the fall of 2001 and was relocated in two distinct areas during the following spring (Figure 10). In contrast, Fish C moved around the estuary and was relocated more often than the other tagged fish; it was relocated north of West Pass during the fall of 2001 and the beginning of the spring of 2002, then moved closer to Alligator Pass in the later part of the spring of 2002 (Figure 11). Fish Q was relocated in the estuary on three consecutive days, between Alligator Pass and East Pass, during the spring of 2002 (Figure 12). Utilization distributions of relocations of Gulf sturgeon in the fall of 2001 (n = 10), and the spring of 2002 (n = 28), were both mostly confined to the Main Suwannee tracking area (Figures 13 and 14). However, the utilization distributions calculated for

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27 the fall, compared to those calculated for the spring, exhibited differences. The observed area used by sturgeon in the fall of 2001 appears larger than the observed area used in the spring of 2002 (Figures 13 and 14). Apparent differences may be because relocations of sturgeon in the fall of 2001 were less frequent (Table 3), farther away from the closest mouth of the Suwannee River (Paired, two tailed, t-test, t = 1.91 n = 39, P = 0.064), and more dispersed within the studied area, than relocations were in the spring of 2002. In addition, the most highly used area, the 50% UD, in the spring of 2002, was outside Alligator Pass, whereas in the fall of 2001, the most highly used area was divided between the area north of West Pass and the area around Alligator Pass. Despite differences in patterns of use, areas north of West Pass and adjacent to Alligator Pass, were highly used by Gulf sturgeon during both seasons (Figures 13 and 14). Distribution of Benthic Invertebrates and Sediment Types Sand was the major component of the sediment on a percentage basis at most of the benthic core sites (n = 28), ranging from 12.8 to 86.4% (58.8%, 16.8). Very Fine Sand comprised 5.4 to 50.0% (25.2% 13.5) of the sediment at each core site. Percent Oyster Shell at core sites ranged from 0.6 to 67.0% (9.9% 13.6) and percent Small Shell was usually low, but constant across all sites ranging from 5.3 to 15.0% (6.1% 3.6). Mean and first standard deviation for the sediment size types from the five samples collected at each of the 28 benthic core sites is presented in Table 4. Abundance and biomass of all invertebrates found in benthic cores collected from the Suwannee River estuary, excluding polychaetes, are listed in Table 5. In all 28 cores collected, the relative total abundance of all phyla was comprised of 82.5% arthropods (crustaceans), 7.9% brachiopods, 2.8% echinoderms (brittle stars and sand dollars), and 6.7% molluscs (bivalves and gastropods) (Table 5, Figure 15). On a relative basis,

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28 arthropods comprised 27.7%, brachiopods 20.2%, echinoderms 32.1%, and molluscs 20.12%, of the total invertebrate biomass collected from cores (Table 5, Figure 16). Although polychaetes could not be accurately identified, it was determined that members of seven families were present: Glyceridae, Onuphidae, Opheliadae, Oweniidae, Pectinaridae, Pilargidae, and Polynoidae. Significant differences were observed in the relative abundance and absolute number of genera collected by the core method compared to the petite ponar grab method. Specifically, there was a significant difference in the relative abundance of the eight major invertebrate groups collected (amphipods, bivalves, brachiopods, brittle stars, decapods, gastropods, isopods and sand dollars) in five out of the six comparisons made between cores and grabs (Fishers exact tests, n = 8, P <0.01) (Table 6). However, in one comparison, in which sand was the predominant sediment type, no difference between the two methods was detected (Fishers exact test, n = 8, P = 0.38). In addition significantly more genera were collected by the core method compared to the petite ponar grab method (Friedman Test, n = 6, S = 6.00, P < 0.02) (Table 6). Relocations of Gulf Sturgeon in Relation to Environmental Parameters, and Benthic Invertebrate Distribution Environmental Parameters Bottom water temperatures at relocation positions of Gulf sturgeon during the fall of 2001 ranged from 20.0 to 22.8 C (21.4 0.9 C). In the spring of 2002, bottom temperatures at relocations ranged from 18.4 to 26.5 C (22.8 2.3 C). Bottom temperatures at fall 2001 positions were significantly colder than bottom temperatures at relocations in the spring of 2002 (Paired, two-tail, t-test n = 38, t = -3.14, P = 0.004) (Figure 17).

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29 Bottom salinities at relocation positions of Gulf sturgeon during the fall of 2001 ranged from 21.6 to 35.1 ppt (29.2 3.9 ppt) and bottom salinities during the spring of 2002 ranged from 15.2 to 31.2 ppt (23.3 5.1 ppt). Average bottom salinity at positions in the fall of 2001 was significantly higher than that of the spring of 2002 (Satterthwaite Unequal Variance, two-tail, t-test, n = 36, t = 2.69, P = 0.011) (Figure 17). Dissolved oxygen concentrations near the bottom at relocation positions ranged from 6.0 to 9.8 mg/L (7.4 1.0 mg/L). No significant difference was detected between average dissolved oxygen near the bottom at positions during the fall of 2001 compared to those in the spring of 2002 (Satterthwaite Unequal Variance, two-tail, t-test, n = 38, t = 0.15, P = 0.886). Relocations of Gulf sturgeon during the fall of 2001 were not significantly correlated with any of the tested environmental variables at the = 0.1 level (Table 7). However, relocations during the spring of 2002 were positively correlated with dissolved oxygen, and negatively correlated with Oyster Shell and Small Shell (Spearman Rank Correlation test, P < 0.1) (Table 8). In addition, when sediment type was clustered using the Wards minimum variance method, and area within each cluster was compared to the frequency of relocations of Gulf sturgeon within that cluster, relocations were significantly distributed according to sediment type (Fishers exact test, n = 4, P <0.001) (Figures 18 and 19, Table 9). When compared to the area within each sediment cluster, the frequency of relocations was comparatively highest in cluster number 2. Sites in cluster 2 were 76.4 to 86.4% Sand, 6.4 to 14.8% Very Fine Sand, and < 8% Small Shell and Oyster Shell (Figure 19, Tables 9 and 10).

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30 Invertebrate Distribution No correlation was detected between relocations of Gulf sturgeon in the fall of 2001 and relocations in the spring of 2002 (Spearman Rank Correlation test, = 0.00134, P = 0.99); however, both fall 2001 and spring 2002 relocations were significantly correlated with the abundance and biomass of Glottidia pyramidata (Tables 11 and 12). In addition, relocations in the fall of 2001 were significantly positively correlated with the abundance and biomass of two brittle star genera: Amphipholis and Ophiactis, molluscs: Corbula, Crassinella, and Parvilucina, and crabs: Euryplax and Portunus (Spearman Rank Correlation test, P < 0.1) (Table 11). Relocations in the spring of 2002 were significantly positively correlated with the biomass of the amphipod Ampelisca as well as the abundance and biomass of the clam Ensis (Spearman Rank Correlation test, P < 0.1) (Table 12). Relocations of Gulf sturgeon within the Main Suwannee tracking area (MSTA) during the fall of 2001 and the spring of 2002 (n = 38) were not significantly distributed according to total invertebrate biomass (Fishers exact test, n = 4, P = 0.106) (Table 13, Figures 20 and 21). However, when compared to the area within each cluster, frequency of relocations of sturgeon was comparatively highest in cluster number 4, the cluster with the lowest overall invertebrate biomass (Figure 21, Tables 13 and 14). Relocations during the fall of 2001 and the spring of 2002 were significantly distributed according to both the abundance and the biomass of the Gulf sturgeons main prey resources (Murie and Parkyn 2002): amphipods (Ampelisca), brachiopods (Glottidia pyramidata), and brittle stars (Amphiuridae and Ophiactidae) (Abundance: Fishers exact test, n = 5, P <0.001, Biomass: Fishers exact test, n = 4, P<0.002) (Figures 22-25, Tables

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31 15-18). When compared to area within each prey abundance cluster, the frequency of relocations of Gulf sturgeon was comparatively highest in cluster number 3. Cluster number 3 had high abundances of all prey resources and the highest numeric abundance of brachiopods, the dominant prey organism observed in stomach contents. In addition, the frequency of relocations of sturgeon on a unit area basis was lowest in clusters 2 and 5, which had the lowest average number of brachiopods (Figure 23, Tables 15 and 16). However, when relocations of Gulf sturgeon were compared on a unit basis to area within each prey biomass cluster, the frequency of relocations of sturgeon was comparatively highest in cluster 2 followed by cluster 3, which had low to medium prey biomass (Figure 25, Tables 17 and 18). Relocations of Gulf sturgeon during the fall of 2001 and the spring of 2002 sampling periods were significantly distributed according to both the abundance and the biomass of brachiopods (Abundance: Fishers exact test, n = 4, P < 0.001, Biomass: Fishers exact test, n = 4, P = 0.007) (Figures 26-31, Tables 19-22). When compared to the area within each brachiopod abundance cluster, frequency of relocations of Gulf sturgeon was comparatively highest in cluster number 4. Cluster number 4 also had the highest overall abundance of brachiopods. In addition, the frequency of relocations of sturgeon on a unit area basis was lowest in cluster 2, which had no brachiopods (Figure 27, Tables 19 and 20). Relocations of Gulf sturgeon appear distributed in the Suwannee River estuary in a pattern similar to the abundance of brachiopods (Figure 28). When compared to the area within each brachiopod biomass cluster, the frequency of relocations of sturgeon was comparatively the highest in cluster 2, which had low/medium brachiopod biomass (Figure 30, Tables 21 and 22). Relocations of Gulf

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32 sturgeon did not appear distributed in a similar pattern as that of brachiopod biomass (Figure 31). Environmental Parameters and Benthic Invertebrate Distribution Canonical correspondence analysis (CCA) was used to explore the relationship between the numerical abundance of invertebrates, the frequency of relocations of Gulf sturgeon during the fall and the spring, and the tested environmental parameters in the Suwannee River estuary. The first three axes in the CCA of genera abundances in relation to the seven tested environmental variables (Very Fine Sand, Sand, Small Shell, Oyster Shell, Distance from the closest mouth of the Suwannee River (DFRM), Dissolved Oxygen, and Depth), explained 33.0% of the variation in the invertebrate data matrix (Table 23). The first canonical axis, which explained 15.4% of the variation, was highly positively correlated (>0.399) with DFRM and Depth and negatively correlated with Very Fine Sand. The second canonical axis, which explained 11.0% of the variation, was highly positively correlated (>0.399) with Very Fine Sand, and negatively correlated with Small Shell and Oyster Shell. The third canonical axis, which explained 6.7% of the variation, was positively correlated (>0.399) with Depth and Very Fine Sand and negatively correlated with Sand (Tables 23 and 24). Dissolved Oxygen was not as highly correlated with any axis as the other environmental parameters were and therefore did not explain as of much variation in the invertebrate community (Table 24). Many genera appear to have been ordinated in response to an environmental gradient in the Suwannee River estuary. Habitats varied from inshore, shallow habitats characterized by Very Fine Sand, inhabited by genera such as the amphipod Ampelisca, the brittle star Amphiodia, and the crab Pinnixa, to deeper, more offshore habitats, inhabited by genera such as molluscs: Pyramidella, Marginella, Solemya, and Olivella.

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33 There are a number of genera; however, such as the crab Eurypanopeus, and the gastropods Cantharus and Nassarius, which appear to be more associated with Oyster Shell, than they are with the above described gradient (Table 25, Figure 32). When collected in the field, these genera were mostly associated with living Oyster bar in the Suwannee River estuary. The frequency of relocations of Gulf sturgeon in the fall of 2001 and those in the spring of 2002 had relatively high scores on the first, followed by the third canonical axes, associating relocations more with the combinations of environmental parameters described by those axes. However, relocations of sturgeon in the fall of 2001 had a positive score on the first axis, whereas that score for the spring of 2002 was negative, illustrating a difference in habitat use during these two seasons (Table 25). Canonical correspondence analysis scores for relocations in the fall of 2001 associated sturgeon, during this season, with more offshore areas over sediments with a low percentage of Very Fine Sand, but comprised more highly of Sand/Small Shell. In contrast, relocations in the spring of 2002 were more associated with inshore, shallow areas, over mixed sediments (Tables 24 and 25). Neither fall 2001, nor spring 2002 relocation scores were exactly coincident with any of their major prey resources in the Suwannee River estuary; amphipods, brachiopods, and brittle stars (Amphiodia, Amphipholis, Ophiophragmus, and Ophiactis); however, spring 2002 relocation scores on each axis more closely resembled those of some of their prey resources than did relocations in the fall, 2001 (Figures 32 and 33). Glottidia, the sturgeons main prey resource in the Suwannee River estuary (Murie and Parkyn 2002), had a high negative score for canonical axis three, illustrating

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34 that this genera was more associated with shallow, sandy habitats with low Very Fine Sand content (Table 25, Figures 32 and 33). Invertebrates were also grouped at the family level to allow for comparison of the effects of taxonomic level on how invertebrate abundance is ordinated in relation to environmental parameters. The first three axes in the CCA of the abundance of invertebrates at the family level in relation to the seven tested environmental variables: Very Fine Sand, Sand, Small Shell, Oyster Shell, DFRM, Dissolved Oxygen, and Depth, explained 38.2.0% of the variation in the data (Table 26). The first canonical axis, which explained 19.1% of the variation, was highly negatively correlated with Small Shell and Oyster Shell. The second canonical axis, which explained 12.2% of the variation, was highly positively correlated with Small Shell, Depth, and DFRM and negatively correlated with Very Fine Sand. The third canonical axis, which explained 6.9% of the variation, was positively correlated with Sand and negatively correlated with Very Fine Sand and Depth (Tables 26 and 27). As seen in the CCA at the genera level, Dissolved Oxygen was not as highly correlated to any of the canonical axes as the other environmental variables, indicating that Dissolved Oxygen contributed less to the structuring of the community than did other environmental parameters (Table 27). Overall, the canonical correspondence analysis at the family level did not appear to differ greatly from analysis at the genera level (Figures 32 and 34). The three basic habitat types: 1) high percentage Very Fine Sand and close to a mouth of the Suwannee River; 2) high percentage Oyster Shell; 3) and deep and away from a mouth of the Suwannee River, were still observed, but there was a greater emphasis on Oyster Shell habitat when analysis was conducted at the family level (Figure 34).

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35 Canonical correspondence analysis of relocations of Gulf sturgeon in the fall of 2001 and in the spring of 2002 at the family level had the highest scores on the second followed by the third canonical axes (Table 28). As seen in the analysis conducted at the genera level, fall 2001 relocations were more associated with areas farther offshore over sediments with higher Sand and Small Shell composition and lower Very Fine Sand composition, while spring 2002 relocations were associated with shallower, more inshore habitats (Tables 27 and 28).

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36 Table 3. Duration of residency in the Suwannee River estuary by each ultrasonic-tagged Gulf sturgeon during the study period from November 2001 through May 2002. Interval was calculated as the time in days between the Start Date and the End Date; Start Date refers to the date when the fish was first relocated in the estuary; End Date refers to the date when the fish was last relocated in the estuary; R = the number of days that an individual fish was relocated; M = Male; F = Female; and NR = Not Relocated. Fall 2001 Spring 2002 Fish Identifier Sex Start Date End Date Interval (Days) R Start Date End Date Interval (Days) R A M 12/15 12/15 1 1 NR B M NR 3/14 3/14 1 1 C M 12/15 12/19 5 2 3/18 4/17 31 7 D M 11/11 11/11 1 1 NR E M 11/20 11/20 1 1 NR F M 12/10 12/15 6 2 3/17 3/17 1 1 G M 12/2 12/2 1 1 4/10 4/17 8 5 H M 11/7 11/7 1 1 3/24 4/15 23 6 I M NR NR J M NR NR K M NR NR L M NR NR M F 11/18 11/18 1 1 3/29 4/10 13 3 N F NR 3/28 3/28 1 1 O F NR 4/14 4/14 1 1 P F NR 3/14 3/14 1 1 Q F NR 3/16 3/18 3 3 R F NR NR

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37 Table 4. Mean and first standard deviation of each sediment size type collected from 28 benthic core location sites in the Suwannee River estuary, Florida. Five cores were collected from each core site from April 22 through May 9, 2002. At each core site, sediment was collected from a central location and then collected from four satellite locations (all 30.5 m from the central location) by swimming bearings of 50, 140, 230 and 320 degrees from the central location. Site Very Fine Sand ( Xs1 d ) Sand ( Xs1 d ) Small Shell ( Xs1 d ) Oyster Shell ( Xs1 d ) 2X 15.4 4.6 53.6 9.2 6.6 1.5 24.4 11.8 2Y 10.8 5.5 68.6 13.0 11.2 5.0 9.4 6.3 2Z 10.0 0 80.0 3.5 5.5 2.7 4.5 1.1 3X 27.0 11.0 65.6 10.9 2.9 1.2 4.5 3.3 3Y 11.0 5.5 76.4 6.1 7.6 2.5 5.0 2.1 3Z 27.0 8.4 58.2 7.8 8.0 2.1 6.8 3.4 4X 25.4 8.6 66.4 7.1 4.4 1.3 3.8 1.1 4Y 14.0 3.8 76.4 5.8 5.4 1.8 4.2 1.6 4Z 17.0 7.0 64.2 6.9 8.8 1.6 10.0 5.9 5X 35.0 15.4 47.0 14.6 4.0 1.4 14.0 5.7 5Y 20.0 7.1 72.2 6.5 3.3 1.6 4.5 2.4 5Z 17.6 5.6 51.4 15.3 13.2 2.0 17.8 11.1 6X 46.0 4.2 43.2 5.4 5.2 0.4 5.6 1.3 6Y 5.4 4.6 12.8 6.6 14.2 6.9 67.6 17.0 6Z 20.1 8.4 63.6 12.2 6.8 1.6 9.5 5.7 7X 38.6 12.4 50.0 14.3 5.0 0.0 6.4 2.2 7Y 38.0 9.7 49.2 10.3 5.9 2.6 6.9 3.1 7Z 23.8 9.9 24.6 0.9 15.0 3.1 36.6 7.3 8X 35.0 15.8 63.6 15.6 0.8 0.3 0.6 0.4 8Y 35.0 11.2 58.6 11.0 3.2 1.8 3.2 1.8 8Z 6.4 2.7 80.0 14.2 6.2 5.0 7.4 11.1 9X 46.0 9.6 46.2 13.1 4.2 1.8 3.6 2.2 9Y 37.0 2.7 57.1 4.3 3.2 1.8 2.7 1.4 9Z 26.0 13.4 60.0 10.6 8.0 2.7 6.0 2.2 S1 7.2 5.1 86.4 6.1 2.7 1.3 3.7 3.5 S2 14.8 3.2 80.1 3.6 2.3 0.3 2.8 1.3 S3 50.0 15.0 43.6 13.0 3.2 1.0 3.2 1.0 S4 46.0 2.6 47.2 2.2 4.2 1.1 2.6 1.3

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38 Table 5. Density in abundance and biomass of all invertebrates, excluding polychaetes, collected from benthic core sites in the Suwannee River estuary, Florida. Ten cores, (surface area = 81 cm 2 ; volume = 1234 cm 3 ) were collected from 28 cores from April 22 through May 9, 2002. All organisms retained by a 0.85 mm sieve or coarser were collected. Phylum Family Genus Species Abundance/m 2 Biomass (g) / m 2 Arthropoda Alpheidae Alpheus armillatus 0.3304 0.0459 Alpheus sp. 0.1101 0.0008 Ampeliscidae Ampelisca verrilli 40.6388 0.3108 vadorum 37.8855 0.1504 Anthuridae Apanthura magnifica 2.9736 0.0178 Cyathura polita 1.9824 0.0211 Balanidae Balanus cf. eberneus 313.7665 1.5135 Callianassidae Callianassa sp. 0.2203 0.0032 Goneplacidae cf. Euryplax nitida 0.2203 0.0078 Hippolytidae Latreutes parvulus 0.1101 0.0008 Nannasticidae Oxyurostylis smithi 0.5507 0.0020 Paguridae Pagurus longicarpus 0.7709 0.0451 Penaeidae Parapenaeus politus 0.1101 0.0015 Pinnotheridae Pinnixa sp. 0.6608 0.0128 Porcellanidae Euceramus praelongus 0.3304 0.0081 Petrolisthes armatus 0.2203 0.1028 Portunidae Pontunus floridanus 0.1101 0.0416 Xanthidae Eurypanopeus depressus 3.6344 1.0021 Brachiopoda Lingulidae Glottidia pyramidata 38.8767 2.3800 Chordata Branchiostomidae Branchiostoma sp. 0.1101 0.0010 Echinodermata Amphiuridae Amphiodia atra 1.7621 0.4291 Amphipholis gracillima 5.6167 0.7977 Ophiophragmus filograneus 2.6432 0.4897 wurdemani 0.5507 0.2132 Mellitidae Mellita tenuis 0.5507 1.7060 Ophiactidae Ophiactis sp. 2.6431 0.1915 Mollusca Arcidae Anadara transversa 0.1101 <0.0001 Buccinidae Cantharus cancellarius 0.6608 0.0963 Corbulidae Corbula contracta 0.3304 0.0038 Crassatellidae Crassinella lunulata 0.1101 0.0006 Crepidulidae Crepidula plana 3.0837 0.0485 Lucinidae Parvilucina multilineata 0.1101 0.0011 Mactridae Mactra fragilis 0.1101 0.0175 Marginellidae Marginella apicina 4.5154 0.1425 Melongenidae Melongena corona 0.1101 1.2343 Muricidae Calotrophon ostrearum 0.1101 0.0025 Mytilidae Amygdalum papyrium 0.3304 0.0156 Brachidontes exustus 6.3877 0.1238 Ischadium recurvum 2.4230 0.0822 Nassariidae Nassarius vibex 0.6608 0.0342 Naticidae Natica pusilla 0.3304 0.0058 Nuculanidae Nuculana acuta 0.2203 0.0170 Olividae Olivella floralia 2.3128 0.1622 Pyramidellidae Boonea impressa 2.423 0.0072 Pyramidella crenulata 0.5507 0.0050 Solemyidae Solemya occidentalis 1.1013 0.1655 Solenidae Ensis minor 0.8811 0.0369 Tellinidae Tellina cf. texana 5.1762 0.1189 Tellina cf. versicolor 1.6520 0.1179 Terebridae Terebra dislocata 0.1101 0.1874 Ungulinidae Diplodonta semiaspera 1.3216 0.0750

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39 Table 6. Comparisons between the core and petite ponar grab methods for the collection of invertebrates in the Suwannee River estuary, Florida, in terms of total number of genera collected and relative abundance of invertebrate groups. Fishers exact tests were used to determine differences in relative abundance of the eight invertebrate groups (amphipods, brachiopods, bivalves, brittle stars, decapods, gastropods, isopods, and sand dollars) found at these six sites. Cores were collected from April 22 through May 9, 2002. Grabs were collected from February 24 through March 30, 2002. Site Predominant Sediment Type Number of Genera Collected by Core Method Number of Genera Collected by Grab Method Fishers Exact P value 3X Very Fine Sand 6 3 P < 0.001 5Y Sand 11 6 P = 0.383 7Y Very Fine Sand 9 2 P = 0.004 7Z Small Shell and Oyster Shell 13 2 P < 0.001 8Y Very Fine Sand and Sand 8 6 P < 0.001 9Z Very Fine Sand and Sand 8 4 P < 0.001

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40 Table 7. Spearman Rank Correlations (between relocation positions of Gulf sturgeon in the fall of 2001 and environmental parameters collected from the Suwannee River estuary, Florida, from April 22 through May 9, 2002. No correlations were significant at the P < 0.1 level. DFRM = distance from the closest mouth of the Suwannee River. Environmental Parameter P Very Fine Sand -0.205 0.294 Sand 0.188 0.338 Small Shell 0.018 0.927 Oyster Shell -0.108 0.583 Dissolved Oxygen -0.082 0.680 DFRM 0.048 0.807 Depth 0.012 0.953

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41 Table 8. Spearman Rank Correlations (between relocation positions of Gulf sturgeon in the spring of 2002 and environmental parameters collected from the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Correlations with P < 0.1 are indicated with a and considered significant. DFRM = distance from the closest mouth of the Suwannee River. Environmental Parameter P Very Fine Sand -0.048 0.810 Sand 0.173 0.380 Small Shell -0.384 0.044* Oyster Shell -0.321 0.096* Dissolved Oxygen 0.343 0.074* DFRM -0.237 0.225 Depth -0.274 0.158

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42 Table 9. Cluster number and percentage of each sediment size type at each of the 28 benthic core sites collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Site Cluster Number Very Fine Sand Sand Small Shell Oyster Shell 2X 1 15.4 53.6 6.6 24.4 2Y 1 10.8 68.6 11.2 9.4 3X 1 27.0 65.6 2.9 4.5 3Z 1 27.0 58.2 8.0 6.8 4X 1 25.4 66.4 4.4 3.8 4Z 1 17.0 64.2 8.8 10.0 5Y 1 20.0 72.2 3.3 4.5 5Z 1 17.6 51.4 13.2 17.8 6Z 1 20.1 63.6 6.8 9.5 9Z 1 26.0 60.0 8.0 6.0 2Z 2 10.0 80.0 5.5 4.5 3Y 2 11.0 76.4 7.6 5.0 4Y 2 14.0 76.4 5.4 4.2 8Z 2 6.4 80.0 6.2 7.4 S1 2 7.2 86.4 2.7 3.7 S2 2 14.8 80.1 2.3 2.8 5X 3 35.0 47.0 4.0 14.0 6X 3 46.0 43.2 5.2 5.6 7X 3 38.6 50.0 5.0 6.4 7Y 3 38.0 49.2 5.9 6.9 8X 3 35.0 63.6 0.8 0.6 8Y 3 35.0 58.6 3.2 3.2 9X 3 46.0 46.2 4.2 3.6 9Y 3 37.0 57.1 3.2 2.7 S3 3 50.0 43.6 3.2 3.2 S4 3 46.0 47.2 4.2 2.6 6Y 4 5.4 12.8 14.2 67.6 7Z 4 23.8 24.6 15.0 36.6

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43 Table 10. Area within each sediment cluster compared to the frequency of relocations of Gulf sturgeon within that cluster. Sediment was collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Polygons representing each core site were created by interpolation between core location points using a Thiessen polygon interpolation method. Core sites with the same cluster number were then grouped and area within each cluster was calculated (ArcView 3.2). Cluster Number Cluster Area (km 2 ) Frequency of Sturgeon Relocations Frequency of Sturgeon Relocations/Cluster Area 1 60.7 6 0.10 2 28.0 20 0.71 3 45.7 10 0.22 4 9.3 2 0.22

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44 Table 11. Spearman Rank Correlations ( between relocation positions of Gulf sturgeon in the fall of 2001 and the abundance and biomass of all invertebrate genera (excluding polychaetes) collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Correlations with a P < 0.1 are indicated with a and considered significant. Phylum Genus Abundance () Abundance (P) Biomass ( ) Biomass (P) Arthropoda Alpheus 0.218 0.266 0.194 0.323 Ampelisca -0.122 0.537 -0.077 0.698 Apanthura 0.108 0.585 0.101 0.611 Balanus -0.089 0.651 -0.089 0.651 Callianassa -0.129 0.514 -0.129 0.514 Cyathura -0.215 0.272 -0.215 0.272 Euceramus -0.161 0.414 -0.160 0.415 Eurypanopeus 0.108 0.585 0.118 0.551 cf. Euryplax 0.540 0.003* 0.536 0.004* Latreutes -0.089 0.651 -0.089 0.651 Oxyurostylis 0.074 0.708 0.083 0.675 Pagurus -0.040 0.841 -0.025 0.901 Parapenaeus -0.089 0.651 -0.089 0.651 Petrolisthes -0.089 0.651 -0.089 0.651 Pinnixa -0.216 0.270 -0.215 0.272 Portunus 0.375 0.049* 0.375 0.049* Brachiopoda Glottidia 0.361 0.059* 0.373 0.051* Chordata Branchiostoma -0.089 0.651 -0.089 0.651 Echinodermata Amphiodia -0.115 0.562 -0.090 0.649 Amphipholis 0.448 0.017* 0.500 0.007* Mellita 0.098 0.620 0.098 0.620 Ophiactis 0.431 0.022* 0.400 0.035* Ophiophragmus -0.081 0.684 -0.080 0.686 Mollusca Amygdalum -0.129 0.514 -0.129 0.514 Anadara -0.089 0.651 -0.089 0.651 Brachidontes -0.089 0.651 -0.089 0.651 Boonea -0.089 0.651 -0.089 0.651 Calotrophon -0.089 0.651 -0.089 0.651 Cantharus -0.189 0.336 -0.189 0.336 Corbula 0.375 0.049* 0.375 0.049* Crassinella 0.375 0.049* 0.375 0.049* Crepidula -0.129 0.514 -0.129 0.514 Ensis 0.138 0.485 0.183 0.350 Ischadium -0.129 0.514 -0.129 0.514 Mactra -0.089 0.651 -0.089 0.651 Marginella 0.188 0.338 0.128 0.516 Melongena -0.089 0.651 -0.089 0.651 Nassarius -0.242 0.214 -0.240 0.219 Natica -0.129 0.514 -0.129 0.514 Nuculana -0.129 0.514 -0.129 0.514 Olivella -0.241 0.217 -0.240 0.219 Parvilucina 0.375 0.049* 0.375 0.049* Pyramidella 0.128 0.518 0.138 0.485 Solemya -0.160 0.415 -0.160 0.415 Tellina -0.241 0.216 -0.257 0.188 Terebra -0.089 0.651 -0.089 0.651

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45 Table 12. Spearman Rank Correlations (between relocation positions of Gulf sturgeon in the spring of 2002 and the abundance and biomass of all invertebrate genera (excluding polychaetes) collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Correlations with a P < 0.1 are indicated with a and considered significant. Phylum Genus Abundance () Abundance (P) Biomass () Biomass (P) Arthropoda Alpheus -0.054 0.783 -0.039 0.844 Ampelisca 0.243 0.213 0.344 0.073* Apanthura 0.301 0.120 0.261 0.179 Balanus 0.117 0.554 0.117 0.554 Callianassa -0.262 0.178 -0.262 0.179 Cyathura 0.060 0.761 0.047 0.811 Euceramus -0.062 0.753 -0.062 0.753 Eurypenopeus 0.037 0.850 0.031 0.875 cf. Euryplax -0.262 0.178 -0.258 0.194 Latreutes -0.182 0.355 -0.182 0.355 Oxyurostylis -0.168 0.394 -0.143 0.469 Pagurus 0.116 0.557 0.065 0.744 Parapenaus 0.117 0.554 0.117 0.554 Petrolithes 0.117 0.554 0.117 0.554 Pinnixia 0.184 0.349 0.186 0.344 Portunas -0.182 0.355 -0.182 0.355 Brachiopoda Glottidia 0.514 0.005* 0.410 0.030* Chordata Branchiostoma -0.182 0.355 -0.182 0.355 Echinodermata Amphiodia 0.200 0.307 0.195 0.320 Amphipholis 0.042 0.834 0.021 0.917 Mellita -0.327 0.090* -0.326 0.090* Ophiactis -0.217 0.268 -0.211 0.280 Ophiofragmous -0.036 0.854 -0.054 0.786 Mollusca Amydalum 0.168 0.392 0.168 0.392 Anadara -0.182 0.355 -0.182 0.355 Brachiodontes -0.182 0.355 -0.182 0.355 Boonea -0.182 0.355 -0.182 0.355 Calotrophon -0.182 0.355 -0.182 0.355 Cantharus 0.285 0.142 0.276 0.155 Corbula -0.182 0.355 -0.182 0.355 Crassinella -0.182 0.355 -0.182 0.355 Crepidula 0.168 0.392 0.168 0.392 Ensis 0.449 0.017* 0.461 0.014* Ishadium 0.168 0.392 0.168 0.392 Mactra -0.182 0.355 -0.182 0.355 Marginella -0.361 0.059* -0.287 0.139 Melongena -0.182 0.355 -0.182 0.355 Nassarius 0.112 0.572 0.075 0.705 Natica 0.168 0.392 0.168 0.392 Nuculana 0.168 0.392 0.168 0.392 Olivella -0.365 0.056* -0.360 0.060* Parvilucina -0.182 0.355 -0.182 0.355 Pyramidella -0.327 0.090* -0.326 0.090* Solemya -0.326 0.090* -0.326 0.090* Tellina -0.226 0.248 -0.450 0.016* Terebra -0.182 0.355 -0.182 0.355

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46 Table 13. Cluster number and total invertebrate biomass (excluding polychaetes) at each benthic core site collected from the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Site Cluster Number Invertebrate Biomass 2X 1 12.0985 3X 1 9.0836 4X 1 7.1875 8Z 1 13.4400 6Y 2 24.8926 2Y 3 2.7734 3Y 3 3.7442 5Y 3 3.6717 8Y 3 4.0191 9X 3 2.4818 9Y 3 3.6903 S3 3 3.1500 2Z 4 0.6318 3Z 4 1.6278 4Y 4 1.6589 4Z 4 0.7329 5X 4 0.3383 5Z 4 0.8054 6X 4 0.4825 6Z 4 1.2888 7X 4 0.2980 7Y 4 1.7902 7Z 4 1.8007 8X 4 0.2473 9Z 4 1.3653 S1 4 1.5019 S2 4 1.1823 S4 4 0.0475

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47 Table 14. Area within each total invertebrate biomass cluster compared to the frequency of relocations of Gulf sturgeon within that cluster. Invertebrates were collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Polygons representing each core site were created by interpolation between core location points using a Thiessen polygon interpolation method. Core sites with the same cluster number were then grouped and area within each cluster was calculated (ArcView 3.2). Cluster Number Cluster Area (km 2 ) Frequency of Sturgeon Relocations Frequency of Sturgeon Relocations/Cluster Area 1 26.7 3 0.11 2 3.6 1 0.28 3 35.1 6 0.17 4 78.2 28 0.36

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48 Table 15. Cluster number and numerical abundance of major prey resources: amphipods (Ampelisca), brachiopods (Glottidia pyramidata), and brittle stars (Amphiuridae and Ophiactidae), at each of the 28 benthic core sites collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Prey abundances were log 10 (x +1) transformed to reduce variation between the invertebrate families. Site Cluster Number Amphipods Brachiopods Brittle stars 2X 1 32 1 3 9X 1 25 0 8 9Y 1 16 1 23 S3 1 6 0 18 5X 2 11 0 0 6X 2 71 0 0 7X 2 278 0 0 S4 2 39 0 0 3X 3 50 34 5 4X 3 34 51 1 5Y 3 13 9 3 7Y 3 151 11 4 8Y 3 54 14 15 S1 3 24 68 1 S2 3 52 124 0 2Y 4 1 13 2 3Y 4 0 19 0 4Y 4 0 3 5 6Z 4 0 2 3 7Z 4 0 2 3 2Z 5 0 0 0 3Z 5 0 0 0 4Z 5 2 1 2 5Z 5 0 0 0 6Y 5 1 0 1 8X 5 0 0 0 8Z 5 0 0 0 9Z 5 7 0 7

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49 Table 16. Area within each prey abundance cluster compared to the frequency of relocations of Gulf sturgeon within that cluster. Prey invertebrates were collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Polygons representing each core site were created by interpolation between core location points using a Thiessen polygon interpolation method. Core sites with the same cluster number were then grouped and area within each cluster was calculated (ArcView 3.2). Cluster Number Cluster Area (km 2 ) Frequency of Sturgeon Relocations Frequency of Sturgeon Relocations/Cluster Area 1 21.7 4 0.18 2 20.1 1 0.05 3 33.1 21 0.63 4 28.1 10 0.36 5 40.6 2 0.05

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50 Table 17. Cluster number and total biomass of main prey resources: amphipods (Ampelisca), brachiopods (Glottidia pyramidata), and brittle stars (Amphiuridae and Ophiactidae), at each of the 28 benthic core sites collected from the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Site Cluster Number Prey Biomass 2X 1 0.5648 2Z 1 0.3185 4Z 1 0.3053 5Y 1 0.5236 5Z 1 0 6X 1 0.0927 6Y 1 0.0048 6Z 1 0.3924 7X 1 0.2703 7Z 1 0.4996 8X 1 0.0529 8Z 1 0 S4 1 0.0372 2Y 2 2.4412 3Z 2 1.3100 4Y 2 1.0730 5X 2 0.9240 7Y 2 1.4642 9X 2 2.1195 9Z 2 0.9600 S1 2 1.3123 S2 2 1.4771 3Y 3 3.4610 8Y 3 4.0232 9Y 3 2.9378 S3 3 3.0438 3X 4 7.6981 4X 4 7.4140

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51 Table 18. Area within each prey biomass cluster compared to the frequency of relocations of Gulf sturgeon within that cluster. Prey invertebrates were collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Polygons representing each core site were created by interpolation between core location points using a Thiessen polygon interpolation method. Core sites with the same cluster number were then grouped and area within each cluster was calculated (ArcView 3.2). Cluster Number Cluster Area (km 2 ) Frequency of Sturgeon Relocations Frequency of Sturgeon Relocations/Cluster Area 1 69.1 7 0.10 2 45.6 24 0.53 3 16.3 5 0.31 4 12.6 2 0.16

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52 Table 19. Cluster number and abundance of brachiopods, Glottidia pyramidata, at each of the 28 benthic core sites collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4) and brachiopod abundances were log 10 (x +1) transformed to reduce the influence of very high abundances. Site Cluster Number Brachiopod Abundance 2X 1 1 4Y 1 3 4Z 1 1 6Z 1 2 7Z 1 2 9Y 1 1 2Z 2 0 3Z 2 0 5X 2 0 5Z 2 0 6X 2 0 6Y 2 0 7X 2 0 8X 2 0 8Z 2 0 9X 2 0 9Z 2 0 S3 2 0 S4 2 0 2Y 3 13 3Y 3 19 5Y 3 9 7Y 3 11 8Y 3 14 3X 4 34 4X 4 51 S1 4 68 S2 4 124

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53 Table 20. Area within each brachiopod abundance cluster compared to the frequency of relocations of Gulf sturgeon within that cluster. Brachiopods were collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Polygons representing each core site were created by interpolation between core location points using a Thiessen polygon interpolation method. Core sites with the same cluster number were then grouped and area within each cluster was calculated (ArcView 3.2). Cluster Number Cluster Area (km 2 ) Frequency of Sturgeon Relocations Frequency of Sturgeon Relocations/Cluster Area 1 36.7 10 0.27 2 62.7 5 0.08 3 25.5 7 0.27 4 18.7 16 0.86

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54 Table 21. Cluster number and biomass of brachiopods, Glottidia pyramidata, at each of the 28 benthic core sites collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Site Cluster Number Brachiopod Biomass 2X 1 0.0016 2Z 1 0 3Z 1 0 4Z 1 0.0001 5X 1 0 5Z 1 0 6X 1 0 6Y 1 0 6Z 1 0.0430 7X 1 0 7Y 1 0.1107 7Z 1 0.1311 8X 1 0 8Z 1 0 9X 1 0 9Y 1 0.0242 9Z 1 0 S3 1 0 S4 1 0 4Y 2 0.6379 5Y 2 0.4381 8Y 2 0.9972 S1 2 0.9335 S2 2 1.0706 2Y 3 2.1814 3Y 3 3.4610 3X 4 5.6801 4X 4 7.1843

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55 Table 22. Area within each brachiopod biomass cluster compared to the frequency of relocations of Gulf sturgeon within that cluster. Brachiopods were collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Polygons representing each core site were created by interpolation between core location points using a Thiessen polygon interpolation method. Core sites with the same cluster number were then grouped and area within each cluster was calculated (ArcView 3.2). Cluster Number Cluster Area (km 2 ) Frequency of Sturgeon Relocations Frequency of Sturgeon Relocations/Cluster Area 1 97.6 14 0.14 2 22.3 20 0.90 3 11.1 2 0.18 4 12.6 2 0.16

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56 Table 23. Results of canonical correspondence analysis (CCA) for benthic invertebrate genera collected from 28 core sites in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Invertebrates not collected from at least 3 sites were removed to reduce the effects of rare taxa. Genera were log 10 (y+1) transformed; proportional data was arcsin(x/100) transformed; all other environmental parameters were log 10 (x+1) transformed. Species environmental correlations were conducted using Pearson tests. Statistic CCA-Axis 1 CCA-Axis 2 CCA-Axis 3 Eigenvalue 0.473 0.337 0.206 Species-Environmental Correlations 0.969 0.951 0.899 % Variance in species data explained by the Axis 15.4 11.0 6.7 Cumulative % of variance in species explained 15.4 26.3 33.0

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57 Table 24. Intraset correlations between the environmental variables examined and the first three axes in the canonical correspondence analysis (CCA) using invertebrate genera collected from 28 core sites in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Intraset correlations may help indicate which environmental variables structure the community; the higher the value, the more the parameter explains variation in the invertebrate data. Proportional data was arcsin(x/100) transformed; all other environmental parameters were log 10 (x+1) transformed; DFRM = Distance from the closest mouth of the Suwannee River. Correlations above 0.399 and below .399 were considered more highly correlated than those between .399 and 0.399 and followed by a for emphasis. Variable CCA-Axis 1 CCA-Axis 2 CCA-Axis 3 Very Fine Sand -0.458* 0.498* 0.544* Sand 0.359 0.041 -0.531* Small Shell 0.382 -0.802* -0.023 Oyster Shell -0.337 -0.846* -0.111 Dissolved Oxygen -0.156 -0.037 -0.278 DFRM 0.616* -0.192 0.092 Depth 0.579* -0.361 0.575*

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58 Table 25. Final scores by genera from the canonical correspondence analysis (CCA). A higher score indicates that the invertebrates distribution was more highly correlated to the environmental variables described by the axis. The canonical correspondence analysis was conducted on genera and environmental variables collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Invertebrates were log 10 (y+1) transformed. Genera CCA-Axis 1 CCA-Axis 2 CCA-Axis 3 Ampelisca -0.451 0.414 -0.021 Amphiodia -0.322 0.281 0.231 Amphipholis -0.093 0.067 0.538 Apanthura 0.012 0.191 -0.199 Cantharus -0.713 -1.044 0.352 Cyathura -1.241 -0.453 0.521 Diplodonta 0.215 -0.204 0.397 Ensis -0.307 0.211 -0.794 Euceramus 0.493 0.139 -0.318 Eurypanopeus -2.263 -3.306 -0.395 Glottidia -0.013 0.273 -0.665 Marginella 1.160 -0.501 -0.223 Mellita 0.608 -0.041 -0.712 Nassarius -0.859 -0.464 -0.175 Olivella 1.331 -0.362 0.192 Ophiophragmus -0.197 0.284 0.590 Ophiactis 0.427 -0.301 0.831 Oxyurostylis -0.050 0.408 -0.178 Pagurus 0.025 0.041 -0.595 Pinnixa -0.729 0.548 1.046 Pyramidella 1.599 -1.056 0.614 Solemya 0.982 -0.477 1.292 Tellina 0.025 0.212 0.414 Sturgeon-Fall 2001 relocations 0.404 -0.041 -0.234 Sturgeon-Spring 2002 relocations -0.452 0.141 -0.304

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59 Table 26. Results of canonical correspondence analysis (CCA) for benthic invertebrate families collected from 28 core sites in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Families not collected from at least 3 sites were removed to reduce the effects of rare taxa. Invertebrates were log 10 (y+1) transformed; proportional data was arcsin(x/100) transformed; all other environmental parameters were log 10 (x+1) transformed;. Species environmental correlations were conducted using Pearson tests. Statistic CCA-Axis 1 CCA-Axis 2 CCA-Axis 3 Eigenvalue 0.498 0.319 0.179 Species-Environmental Correlations 0.977 0.890 0.881 % Variance in species data explained by the Axis 19.1 12.2 6.9 Cumulative % of variance in species explained 19.1 31.3 38.2

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60 Table 27. Intraset correlations between the environmental variables examined and the first three axes in the canonical correspondence analysis (CCA) using invertebrate families collected from 28 core sites in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Intraset correlations may help indicate which environmental variables structure the community; the higher the value, the more the parameter explains variation in the invertebrate data. Proportional data was arcsin(x/100) transformed; all other environmental parameters were log 10 (x+1) transformed; DFRM = Distance from the closest mouth of the Suwannee River. Correlations above 0.399 and below .399 were considered more highly correlated than those between .399 and 0.399 and followed by a for emphasis. Variable CCA-Axis 1 CCA-Axis 2 CCA-Axis 3 Very Fine Sand 0.368 -0.482* -0.704* Sand 0.177 0.252 0.612* Small Shell -0.687* 0.430* 0.099 Oyster Shell -0.943* 0.009 0.141 Dissolved Oxygen -0.125 -0.298 0.105 DFRM 0.311 0.565* -0.013 Depth -0.002 0.766* -0.454*

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61 Table 28. Final scores by family from the canonical correspondence analysis (CCA). A higher score indicates that the invertebrates distribution was more highly correlated to the environmental variables described by the axis. The canonical correspondence analysis was conducted on family and environmental variables collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Invertebrates were log 10 (y+1) transformed. Family CCA-Axis 1 CCA-Axis 2 CCA-Axis 3 Ampeliscidae 0.266 -0.514 -0.116 Amphiuridae 0.246 -0.059 -0.446 Anthuridae 0.004 -0.203 -0.031 Buccinidae -1.669 -0.118 -0.228 Lingulidae 0.337 -0.173 0.655 Marginellidae 0.153 0.955 -0.114 Mellitidae 0.343 0.640 1.167 Mytilidae -2.770 -0.343 -0.059 Nannasticidae 0.366 -0.295 0.205 Nassaridae -0.305 -0.534 0.037 Olividae 0.270 1.787 0.579 Ophiactidae 0.044 0.938 -0.513 Paguridae 0.245 -0.188 0.568 Pinnotheridae 0.244 -0.605 -1.289 Porcellanidae -1.301 -0.181 0.164 Pyramidellidae -1.971 0.796 0.236 Solemyidae 0.045 1.711 -0.769 Solenidae 0.267 -0.117 0.900 Tellinidae 0.248 0.157 -0.328 Ungulinidae 0.109 0.428 -0.252 Xanthidae -2.660 -0.380 0.230 Sturgeon-Fall 2001 relocations 0.219 0.506 0.479 Sturgeon-Spring 2002 relocations 0.095 -0.368 0.195

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62 Fall Spring Figure 4. Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee River estuary, Florida, during the fall of 2001 (November 7 through December 19) and the spring of 2002 (March 14 through April 17). Thirteen of the eighteen tagged Gulf sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were relocated (one position per day is represented) for a total of 39 relocations.

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63 C A C F F M G H D E Figure 5. Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee River estuary, Florida, during the fall of 2001 (November 7 through December 19). Eight out of the eighteen originally tagged Gulf sturgeon, seven males and one female, were relocated (one position per day is represented) for a total of 10 relocations (filled circles). The letter nearest to each relocation point is the unique fish identifier assigned to the specific sturgeon that was relocated (see Table 3).

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64 M M M C C/GC C C C C N H H H H HO G GG H G P B Q Q Q F Figure 6. Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee River estuary, Florida, during the spring of 2002 (March 14 through April 17). Ten of the eighteen originally tagged Gulf sturgeon, five males and five females, were relocated (one position per day is represented) for a total of 29 relocations (filled circles). The letter nearest to each relocation point is the unique fish identifier for the specific sturgeon that was relocated (see Table 3).

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65 Alligator Pass West Pass Figure 7. Patterns of relocations of Gulf sturgeon (n = 39) in the Suwannee River estuary during the fall of 2001 and the spring of 2002 calculated as utilization distributions (UD)(95%, 80%, and 50%) using a fixed kernel method with a least-squares cross-validation smoothing parameter (ArcView 3.2). Solid gray represents the 50% UD; vertical stripes represent the 80% UD; and horizontal stripes represent the 95% UD. The asterisks represents one sturgeon relocation outside the delineated Main Suwannee tracking area (boxed perimeter).

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66 11-18-01 04-10-02 03-30-02 03-29-02 12-15-01 12-10-01 03-17-02 Figure 8. Relocation positions for two individual tagged Gulf sturgeon, Fish F and Fish M, in the Suwannee River estuary, Florida. Fish F is illustrated by open circles and Fish M is illustrated by filled circles. The number closest to each relocation position in the figure is the date when that specific relocation was made.

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67 12-2-01 04-10-02 04-14-02 04-15-02 04-17-02 04-16-02 Alligator Pass Figure 9. Relocation positions (filled circles) for Fish G in the Suwannee River estuary, Florida. The number closest to each relocation position in the figure is the date when that specific relocation was made.

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68 11-07-01 04-13-02 04-14-02 04-15-02 03-24-02 03-28-02 03-29-02 Figure 10. Relocation positions (filled circles) for Fish H in the Suwannee River estuary, Florida. The number closest to each relocation position in the figure is the date when that specific relocation was made.

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69 12-15-01 12-19-01 03-18-02 03-24-02 03-25-02 04-17-02 04-13-02 04-14-02 04-15-02 Alligator Pass West Pass Figure 11. Relocation positions (filled circles) for Fish C in the Suwannee River estuary, Florida. The number closest to each relocation position in the figure is the date when that specific relocation was made.

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70 03-17-02 03-16-02 03-18-02 Alligator Pass East Pass Figure 12. Relocation positions (filled circles) for Fish Q in the Suwannee River estuary, Florida. The number shown closest to each relocation position in the figure is the date when that specific relocation was made.

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71 Alligator Pass West Pass Figure 13. Patterns of relocations of tagged Gulf sturgeon (n = 10) in the Suwannee River estuary during the fall of 2001 calculated as utilization distributions (UD)(95%, 80%, and 50%) using a fixed kernel method with a least-squares cross-validation smoothing parameter (ArcView 3.2). Solid gray represents the 50% UD; vertical stripes represent the 80% UD; and horizontal stripes represent the 95% UD.

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72 Alligator Pass West Pass Figure 14. Patterns of relocations of Gulf sturgeon (n = 29) in the Suwannee River estuary during the spring of 2002 calculated as utilization distributions (UD)(95%, 80%, and 50%) using a fixed kernel method with a least-squares cross-validation smoothing parameter (ArcView 3.2). Solid gray represents the 50% UD; vertical stripes represent the 80% UD; and horizontal stripes represent the 95% UD.

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73 Arthropods Molluscs Echinoderms Brachiopods Figure 15. Total relative abundance of all invertebrate taxa by phylum, except annelids, from all 28 cores collected in the Suwannee River estuary, Florida, April 22 through May 9, 2002.

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74 Brachiopods Arthropods Echinoderms Molluscs Figure 16. Total relative biomass of all invertebrate taxa by phylum, except annelids, from all 28 cores collected in the Suwannee River estuary, Florida, April 22 through May 9, 2002.

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75 15202530Temperature (C) Month 101520253035Salinity (ppt) NovFebJanDecMarApr Figure 17. Temperature and salinity at relocation positions of Gulf sturgeon in the Suwannee River estuary. Temperature and salinity were measured 10 cm above the bottom. Filled circles (n = 38) represent temperature and open circles (n = 36) represent salinity. Measurements were grouped by week.

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76 2X5Z2Y4Z6Z3X4X5Y3Z9Z2Z8ZS13Y4YS25X7X7Y6XS39XS48X8Y9Y6Y7Z 1 2 3 4 Figure 18. Percent sediment size type (Very Fine Sand, Sand, Small Shell, and Oyster Shell) clustered by benthic core site using the Wards minimum variance method (PC-ORD 4). Sediment was collected from benthic cores taken from the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Bold numerals represent the four unique clusters identified using this technique (see Table 9).

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77 2 22314213 Figure 19. Relocations of Gulf sturgeon (filled circles) in the Suwannee River estuary, Florida, in the fall of 2001 (November 7 through December 19) and spring of 2002 (March 14 through April 17) in relation to sediment type from 28 core sites in the Suwannee River estuary. Thirteen out of eighteen tagged sturgeon, eight individuals in the fall of 2001 and ten individuals in the spring of 2002, were relocated (one position per day is represented) for a total of 39 relocations. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Core sites were interpolated to fill the Main Suwannee tracking area (outer boxed perimeter) using a Thiessen polygon interpolation method and grouped according to the cluster (ArcView 3.2). Bold numerals represent the four unique clusters identified using this method (see Figure 18).

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78 2X8Z3X4X6Y2Y9XS33Y5Y9Y8Y2Z6X4Z5Z5X7X8XS43Z4YS17Y7Z6Z9ZS2 1 2 3 4 Figure 20. Total biomass of all invertebrates (excluding polychaetes) clustered by benthic core site using the Wards minimum variance method (PC-ORD 4). Cores collected from all 28 sites (on the Y-axis) in the Suwannee River estuary, Florida, from April 22 through May 9, 2002, were used for the analysis. Bold numerals represent the four unique clusters identified using this technique (see Table 13).

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79 2134 3413 Figure 21. Relocations of all Gulf sturgeon (filled circles) in the Suwannee River estuary, Florida, in the fall of 2001 (November 7 through December 19) and spring of 2002 (March 14 through April 17) in relation to total invertebrate biomass from 28 core sites in the Suwannee River estuary. Thirteen out of eighteen tagged sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were relocated (one position per day is represented) for a total of 39 relocations. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Sites were interpolated to fill the Main Suwannee tracking area (outer boxed perimeter) using a Thiessen polygon interpolation method and grouped according to cluster (ArcView 3.2). Bold numerals represent the four unique clusters identified using this method (see Figure 20).

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80 2X9X9YS35X6XS47X3X8Y7Y5Y4XS1S22Y3Y4Y6Z7Z2Z3Z8X5Z8Z6Y4Z9Z 1 2 3 4 5 Figure 22. Numerical abundance of the Gulf sturgeons main prey resources: amphipods (Ampelisca), brachiopods (Glottidia pyramidata), and brittle stars (Amphiuridae and Ophiactidae), clustered by benthic core site using the Wards minimum variance method (PC-ORD 4). Prey invertebrates were collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Prey resource abundances were log 10 (x +1) transformed to reduce variation between the invertebrate groups. Bold numerals represent the five unique clusters identified using this method (see Table 15).

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81 33445 55252211 Figure 23. Relocations of Gulf sturgeon (filled circles) in the Suwannee River estuary, Florida, in the fall of 2001 (November 7 through December 19) and the spring of 2002 (March 14 through April 17) in relation to the abundance of their main prey resources: amphipods (Ampelisca), brachiopods (Glottidia pyramidata), and brittle stars (Amphiuridae and Ophiactidae) collected from 28 core sites in the Suwannee River estuary. Thirteen out of eighteen tagged sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were relocated (one position per day is represented) for a total of 39 relocations. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Sites were interpolated to fill the Main Suwannee tracking area using a Thiessen polygon interpolation method and grouped according to cluster (ArcView 3.2). Bold numerals represent the five unique clusters identified using this method (see Figure 22).

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82 2X5Y7Z2Z4Z7X6Z5Z8Z6Y6X8XS42Y9X3ZS14Y7YS25X9Z3Y9YS38Y3X4X 1 2 3 4 Figure 24. Total biomass of the Gulf sturgeons main prey resources as seen in stomach contents: amphipods (Ampelisca), brachiopods (Glottidia pyramidata), and brittle stars (Amphiuridae and Ophiactidae), clustered by benthic core site using the Wards minimum variance method (PC-ORD 4). Prey invertebrates were collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Bold numerals represent the four unique clusters identified using this method (see Table 17).

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83 412 1 13222322 1 Figure 25. Relocations of Gulf sturgeon (filled circles) in the Suwannee River estuary, Florida, in the fall of 2001 (November 7 through December 19) and spring of 2002 (March 14 through April 17) in relation to the total biomass of their main prey resources: amphipods (Ampelisca), brachiopods (Glottidia pyramidata), and brittle stars (Amphiuridae and Ophiactidae) collected from 28 core sites in the Suwannee River estuary. Thirteen out of eighteen tagged sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were relocated (one position per day is represented) for a total of 39 relocations. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Sites were interpolated to fill the Main Suwannee tracking area using a Thiessen polygon interpolation method and grouped according to cluster (ArcView 3.2). Bold numerals represent the four unique clusters identified using this method (see Figure 24).

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84 2X4Z9Y4Y6Z7Z2Z6Y8X9Z3ZS45X5Z6X7X8Z9XS32Y8Y3Y5Y7Y3X4XS1S2 1 2 3 4 Figure 26. Abundance of brachiopods Glottidia pyramidata, clustered by benthic core site using the Wards minimum variance method (PC-ORD 4). Brachiopods were collected from the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Brachiopod abundances were log 10 (x +1) transformed to reduce the influence of very high abundances. Bold numerals represent the four unique clusters identified using this method (see Table 19).

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85 13 2 41332212432 Figure 27. Relocations of Gulf sturgeon (filled circles) in the Suwannee River estuary, Florida, in the fall of 2001 (November 7 through December 19) and spring of 2002 (March 14 through April 17) in relation to brachiopod abundance collected from 28 core sites in the Suwannee River estuary. Thirteen out of eighteen tagged sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were relocated (one position per day is represented) for a total of 39 relocations. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Sites were interpolated to fill the Main Suwannee tracking area using a Thiessen polygon interpolation method and grouped according to cluster (ArcView 3.2). Bold numerals represent the four unique clusters identified using this method (see Figure 26).

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86 0 25 25 50 50 100 100 200 200 382 Figure 28. The distribution of ultrasonic-tagged Gulf sturgeon (filled circles) in relation to the distribution of brachiopods (abundance/m 2 ) in the Suwannee River estuary. Thirteen out of eighteen tagged sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were relocated (one position per day is represented) for a total of 39 relocations. Brachiopods were collected from April 22 through May 9, 2002. Interpolation of brachiopod density (abundance/m 2 ) between sites was completed using an inverse distance weighting method in ArcView 3.2.

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87 2X5Y7Z2Z4Z7X6Z5Z8Z6Y6X8XS42Y9X3ZS14Y7YS25X9Z3Y9YS38Y3X4X 3 1 2 4 Figure 29. Biomass of brachiopods Glottidia pyramidata, clustered by benthic core site using the Wards minimum variance method (PC-ORD 4). Brachiopods were collected from the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Bold numerals represent the four unique clusters identified using this method (Table 21).

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88 3114222 Figure 30. Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the fall of 2001 (November 7 through December 19) and the spring of 2002 (March 14 through April 17) in relation to brachiopod biomass collected from 28 core sites in the Suwannee River estuary. Thirteen out of eighteen tagged sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were relocated (one position per day is represented) for a total of 39 relocations. Clustering was completed using the Wards minimum variance method (PC-ORD 4). Sites were interpolated to fill the Main Suwannee tracking area using a Thiessen polygon interpolation method and grouped according to cluster (ArcView 3.2). Bold numerals represent the four unique clusters identified using this method (see Figure 29).

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89 0 2 2 4 4 8 8 16 16 23 Figure 31. The distribution of ultrasonic-tagged Gulf sturgeon (filled circles) in relation to the distribution of brachiopods (biomass/m 2 ) in the Suwannee River estuary. Thirteen out of eighteen tagged sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were relocated (one position per day is represented) for a total of 39 relocations. Brachiopods were collected from April 22 through May 9, 2002. Interpolation of brachiopod density (biomass/m 2 ) between sites was completed using an inverse distance weighting method in ArcView 3.2.

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90 T R Axis 2 A P Brachiopods W B D I H Spring S Fall M C G O Q N F V L U E Axis 1 J Figure 32. Biplot of the canonical correspondence analysis (CCA) of invertebrate genera and relocations of Gulf sturgeon by season, by environmental parameters (CCA axes 1 and 2, represented) for benthic invertebrates collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Bold letters represent invertebrate genera included in the ordination. A = Ampelisca; B = Amphiodia; C = Amphipholis; D = Apanthura; E = Cantharus; F = Cyathura; G = Diplodonta; H = Ensis; I = Euceramus; J = Eurypanopeus; Brachiopods = Glottidia; L = Marginella; M = Mellita; N = Nassarius; O = Olivella; P = Ophiophragmus; Q = Ophiactis; R = Oxyurostylis; S = Pagurus; T = Pinnixa; U = Pyramidella; V = Solemya; W = Tellina; Fall = Sturgeon relocated in the fall of 2001; Spring = Sturgeon relocated in the spring of 2002; S Shell = Small Shell; VF Sand = Very Fine Sand; DFRM = Distance from the closest mouth of the Suwannee River.

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91 V Axis 3 T Q P U C F G W E B O A N R Fall L D I S p rin g J S M Brachio p ods Axis 2 H Figure 33. Biplot of the canonical correspondence analysis (CCA) of invertebrate genera and relocations of Gulf sturgeon by season, by environmental parameters (CCA axes 1 and 3, represented) for benthic invertebrates collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Bold letters represent invertebrate genera included in the ordination. A = Ampelisca; B = Amphiodia; C = Amphipholis; D = Apanthura; E = Cantharus; F = Cyathura; G = Diplodonta; H = Ensis; I = Euceramus; J = Eurypanopeus; Brachiopods = Glottidia; L = Marginella; M = Mellita; N = Nassarius; O = Olivella; P = Ophiophragmus; Q = Ophiactis; R = Oxyurostylis; S = Pagurus; T = Pinnixa; U = Pyramidella; V = Solemya; W = Tellina; Fall = Sturgeon relocated in the fall of 2001; Spring = Sturgeon relocated in the spring of 2002; S Shell = Small Shell; VF Sand = Very Fine Sand; DFRM = Distance from the closest mouth of the Suwannee River.

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92 O T Axis 2 L P E RM Fall G U B F H I R D Brach C Spring Q J F Sand A S N Axis 1 Figure 34. Biplot of the canonical correspondence analysis (CCA) of invertebrate families and relocations of Gulf sturgeon by season, by environmental parameters (CCA axes 1 and 2, represented) for benthic invertebrates collected in the Suwannee River estuary, Florida, from April 22 through May 9, 2002. Bold letters represent invertebrate families included in the ordination. A = Ampeliscidae; B = Amphiuridae; C = Mytilidae; D = Anthuridae; E = Pyramidellidae; F = Buccinidae; G = Ungulinidae; H = Solenidae; I = Porcellanidae; J = Xanthidae; Brach = Lingulidae; L = Marginellidae; M = Mellitidae; N = Nassaridae; O = Olivelidae; P = Ophiactidae; Q = Nannasticidae; R = Paguridae; S = Pinnotheridae; T = Solemyidae; U = Tellinidae; Fall = Sturgeon relocated in the fall of 2001; Spring = Sturgeon relocated in the spring of 2002. ; S Shell = Small Shell; VF Sand = Very Fine Sand; DFRM = Distance from the closest mouth of the Suwannee River.

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CHAPTER 4 DISCUSSION In the present study, Gulf sturgeon were observed to reside in the nearshore waters of the Suwannee River estuary after emigrating from the Suwannee River and prior to continuing their winter migration. In addition, Gulf sturgeon in the present study were observed to return to the Suwannee River estuary in the spring, before re-entering the Suwannee River. Patterns of use of the Suwannee River estuary by Gulf sturgeon in the present study were similar to those observed in prior studies (Carr et al. 1996, Sulak and Clugston 1999). Carr et al. (1996) tracked 16 tagged Gulf sturgeon as they migrated out of the Suwannee River in November and relocated their tagged fish in the Suwannee Sound, south of East Pass, one of the three mouths of the Suwannee River. Their tagged fish also left the Suwannee Sound in December (Carr et al. 1996). Sulak and Clugston (1999) tracked tagged Gulf sturgeon in the Suwannee River estuary from October through December 1996, but were unable to relocate their fish in the estuary or adjacent waters during January 1997. They speculated that the sturgeon may have migrated into marine waters (Sulak and Clugston 1999). Unlike other studies, Gulf sturgeon in the present study were relocated as they returned to the Suwannee River estuary before immigration into the Suwannee River. The Suwannee population of Gulf sturgeon has been observed to behave slightly differently than the Gulf sturgeon population residing in the Choctawatchee Bay system (Fox et al. 2002). Individual Gulf sturgeon in the Choctawatchee system were sometimes not relocated for periods of more than 6 weeks; however, the authors made no comment 93

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94 that suggests that this absence occurred for all tagged individuals or that those individuals that did leave were absent during the same time of the year (Fox et al. 2002). In the present study, as well as in previous studies of the Suwannee population, Gulf sturgeon have been observed to remain in the Suwannee River estuary for a period of time after emigrating from the river and then to leave the estuary later in the winter (Carr et al. 1996, Sulak and Clugston 1999). Fox et al. (2002) examined the relationship between the distribution of Gulf sturgeon and the distribution of benthic invertebrates in the Choctawhatchee Bay system. Gulf sturgeon, in their study, were most often associated with areas exhibiting the lowest overall invertebrate density. One explanation given for this observation was that the sampling methods used did not collect the Gulf sturgeons major prey species in the system: a ghost shrimp, Lepidophthalmus louisianensis, and a snapping shrimp, Leptalpheus forcepts (Fox et al. 2002). Similarly, in the present study, the distribution of relocations of Gulf sturgeon was not significantly associated with total biomass of all invertebrates in the Main Suwannee tracking area (MSTA), but was most often found in areas with low total biomass of all invertebrates. However, in the present study, Gulf sturgeon were significantly associated with areas containing high numerical abundances of the sturgeons major prey resources as observed in stomach contents (Murie and Parkyn 2002): brachiopods, amphipods, and brittle stars. In addition, the distribution of Gulf sturgeon was most highly associated with areas containing high abundances of brachiopods, the dominant prey observed in stomach contents. The results of previous studies on the feeding habits of the Gulf of Mexico sturgeon suggest that sturgeon eat almost exclusively while wintering in estuarine and marine

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95 environments, and fast while in freshwater rivers (Huff 1975, Mason and Clugston 1993, Gu et al. 2001). Sturgeon captured at the mouth of the Suwannee River, at the start of their spring immigration, often have full stomachs (Mason and Clugston 1993, Murie and Parkyn 2002, Personal observation). This suggests that prey are consumed very shortly before migration into the lotic environment. Gulf sturgeon in the Main Suwannee tracking area (MSTA) of the Suwannee River estuary were associated with areas containing high abundances of their prey resources, especially areas with high abundances of brachiopods. From the present study, it could not be firmly concluded if Gulf sturgeon were preferentially feeding on specific resources. However, the similarity in the distribution of Gulf sturgeon relative to the distribution of their prey resources suggests that regions within the Suwannee River estuary, especially those with high abundances of known prey species, are plausible candidates as critical foraging habitat for the Suwannee population of Gulf sturgeon. As previously noted, similar associations between sturgeon distribution and the distribution of their prey resources have been observed for other Acipenser species (McKechnie and Fenner 1971, Buckely and Kynard 1985, Muir et al. 1988, Moser and Ross 1995, Taverny et al. 2002). In addition, it was suggested by Sulak and Clugston (1999), that the pattern of movement exhibited by individual Gulf sturgeon within the Suwannee River estuary resembled searching behavior, possibly indicating that sturgeon were seeking out areas containing high concentrations of prey resources. Tracked fish, in this prior study, were reported to move slowly and continuously along a linear progression for several hours, before exhibiting long periods of non-linear movement in a small area (Sulak and Clugston 1999).

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96 In contrast to the frequency of relocations in relation to the abundance of prey resources, Gulf sturgeon were not associated with areas containing the highest combined biomass of their main prey resources: brachiopods, amphipods, and brittle stars; or the highest biomass of brachiopods alone. Instead, relocations were primarily associated with areas containing low to medium biomass of prey resources together, and of brachiopods alone. Areas with high abundances of prey specimens, especially brachiopods, were often comprised of a mixture of small and large individuals, whereas areas with low abundances of prey specimens, were more often comprised of only medium to large individuals. The reason for the difference in prey size is unknown. It may be that density-dependent growth of the prey populations was occurring; however, an alternative possibility is that these areas characterized by high abundance, but low biomass, may be excellent settlement habitats for brachiopods. A previous study examining the ecology of G. pyramidata, found that this species of brachiopod began spawning in northern Florida in April, when temperatures rose to 20-22 C, and they continued to spawn for 7-9 months (Paine 1963). Brachiopod larvae remained planktonic for a minimum of 3 weeks and then began to settle out. After settlement, dense aggregations of more than 75 individuals per square foot were observed (Paine 1963). Temperatures of 20-22 C were observed in the Suwannee River estuary in mid to late March, possibly initiating spawning in brachiopods. It may be possible that Gulf sturgeon in the Suwannee River estuary consumed many of the larger brachiopods in these areas, before sampling was conducted, but then entered the Suwannee River before a great deal of settlement by the young of the year had occurred. Additional research on the distribution of brachiopods in the Suwannee River estuary before Gulf sturgeon return

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97 to the area in the spring, as well as research on the life cycle of Glottidia pyramidata in the Suwannee River estuary, especially the timing of spawning and the growth rates of larvae and juveniles, would be needed to examine this possibility. The Main Suwannee tracking area of the Suwannee River estuary was characterized by a number of different habitat types. In most nearshore areas, Sand was the most common sediment type; however, in some regions Very Fine Sand was a large component, and in other areas oyster bars were numerous. Depth and salinity gradients further contributed to the complexity of the habitat. Macroinvertebrates appeared distributed in part, in relation to tested environmental parameters within the estuary. Ordination of macroinvertebrates revealed that they were distributed primarily according to the proportion of Very Fine Sand, Distance from the closest mouth of the Suwannee River (DFRM), Depth, Small Shell, and Oyster Shell. Some of the Gulf sturgeons main prey resources (amphipods, and some genera of brittle stars) were most associated with nearshore habitats characterized by Very Fine Sand, rather than more offshore, deep habitats, or habitats associated with oyster bars. Brachiopods were most highly associated with benthos containing a high proportion of Sand, in concordance with previous studies (Paine 1963). The abundance of brachiopods in sandy sediments may have been the reason that the frequency of relocations of Gulf sturgeon, in the present study, were associated with areas comprised primarily of sand. Relocations of Gulf sturgeon in the Suwannee River estuary were also associated with environmental gradients. In both the fall of 2001 and the spring of 2002, Gulf sturgeon were relocated in the Main Suwannee tracking area (MSTA), however, the specific areas where sturgeon were relocated during the two seasons differed. During the

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98 fall of 2001, Gulf sturgeon were relocated in more offshore waters, characterized by lower temperature, higher salinity and lower Very Fine Sand content, than sturgeon relocated during the spring of 2002. It is possible that sturgeon reside farther offshore during the fall and wait for environmental cues to indicate that conditions are optimal to continue their winter migration. In the spring, however, when sturgeon return to the estuary from their winter migration, they may feed in areas closer to one of the three mouths of the Suwannee River. These more nearshore areas would most likely be more influenced by Suwannee River water and would therefore have reduced salinity. Gulf sturgeon may stage in these areas waiting for cues to begin migration up the river. It has been suggested in some previous studies that staging behavior in Gulf sturgeon may be caused by a physiological need to acclimate to changes in salinity when moving from a saltwater to a freshwater environment (Wooley and Crateau 1985, Carr et al. 1996). However, Fox et al. (2002), found little evidence for this hypothesis in their study of Gulf sturgeon in Choctawhatchee Bay. They observed that sturgeon in their study moved from upstream spawning grounds to the bay in less than four days. In addition, juvenile Gulf sturgeon in tanks required little acclimation when moving from freshwater to saltwater (Altinock et al. 1998). Gulf sturgeon may reside in these estuarine areas, not because they need time to physiologically acclimate, but because this strategy enables them to feed as long as possible, while still receiving important migratory cues. It has been suggested that temperature may be an important migratory cue for the Gulf sturgeon. In previous studies, as well as the present study, the disappearance of Gulf sturgeon from the Suwannee River estuary in the winter coincided with a drop in

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99 temperature (Carr et al. 1996, Sulak and Clugston 1999). In addition, it has been hypothesized that emigration from and immigration to the Suwannee River from the estuary may be related to temperature (Wooley and Crateau 1985, Chapman and Carr 1995, Foster and Clugston 1997). In the Kootenai River system, Idaho, the most important factor leading to the initiation of the spawning migration in female white sturgeon, Acipenser transmontanus, was identified as temperature. Unlike Gulf sturgeon, however, white sturgeon in the Kootenai River system, are not anadromous (Paragamian and Kruse 2001). Factors that prompt the migration of anadromous fishes are not well understood (Yako et al. 2002). The timing of migration and spawning for different North American populations of sockeye salmon, Oncorhychus nerka, was primarily related to the temperature regime encountered during their migration (Hodgson and Quinn 2002). For brown trout, Salmo trutta, the timing of migration was affected by temperature as well, but also by the flow regime in a Norwegian river (Jonsson and Jonsson 2002). In Cape Cod Massachusetts, herring, Alosa psedoharengus and A. aestivalis, migrations were correlated to changes in food availability and the lunar phase (Yako et al. 2002). For Atlantic Cod, Gadus morhua, in the Southern Gulf of St. Lawrence, photoperiod most likely played a major role, however, cooling of bottom waters and a change in the size structure of the population may also have affected the timing of their migration (Comeau et al. 2002). More research examining environmental factors that may serve as behavioral releasers for the migration of the Gulf sturgeon while in the Suwannee River estuary would be of interest, especially with the potential for perturbations on the Suwannee Rivers flow rate.

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100 It is not known where the tagged Gulf sturgeon from the present study went during the months of January and February of 2002. Based on previous research, it could be hypothesized that these sturgeon migrated into marine waters and either remained in offshore areas, or overwintered in another estuary system. In previous studies, several Gulf sturgeon that were tagged and tracked in one river system were relocated for a period of time in another nearshore system and in the Gulf of Mexico (Carr et al. 1996, Fox et al. 2002). Because the period of time that the Suwannee population remains in the Suwannee River estuary is relatively short, and Gulf sturgeon appear to feed only in marine and estuarine waters (Huff 1975, Mason and Clugston 1993, Gu et al. 2001), it is suggested that overwintering takes place in nearby marine or estuarine locations. While tracking on a transect approximately 20 km offshore on March 8, 2002, two non-tagged Gulf sturgeon were seen jumping (Figure 35). Ponar grabs taken near the sites where the two sturgeon were observed were comprised of sandy sediments and contained lancelets, Branchiostoma sp. While this observation provides evidence that the Suwannee population of Gulf sturgeon move further offshore than was otherwise observed in the present study, whether the sturgeon were feeding there or simply moving through that area could not be determined. No other sturgeon were observed jumping in that area. More research examining habitat used by the Suwannee population of Gulf sturgeon during the winter months of January and February, when they are also presumably feeding, is warranted to better understand critical habitat for this threatened species. The present study has shown that while in the Suwannee River estuary, Gulf sturgeon are associated with areas containing high abundances of their prey resources, especially brachiopods. Results suggest that regions in the Suwannee River estuary,

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101 especially those containing high abundances of prey resources, may be critical feeding habitat for the Suwannee population of Gulf sturgeon. Sturgeon may actively search out regions containing high abundances of prey resources and remain in those areas until they receive an environmental cue to continue migrating. Alternatively, sturgeon may be selecting specific habitat according to other environmental factors and simply eating whatever prey resources are available there, or it may be a combination of both. Regardless, it could be hypothesized that Gulf sturgeon are eating during their residency in the Suwannee River estuary, at least during the spring time, and therefore the benthos in areas where they were relocated may be very important in the conservation of the species. Degradation of the benthic environment in these areas may reduce the foraging habitat available to the Suwannee population of Gulf sturgeon and therefore reduce their chances for full recovery. Continued research into overwintering habitat and foraging, as well as environmental factors that serve as cues for the timing of migration and feeding, would be of considerable aid in the conservation of this threatened species.

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102 Figure 35. Locations of two non-tagged Gulf sturgeon observed jumping in the Offshore tracking area on March 8, 2002, in relation to the delineated Main Suwannee tracking area (hatched region) and the Offshore tracking area (open region).

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106 Kieffer, M. C., and B. Kynard. 1993. Annual movements of shortnose and Atlantic sturgeons in the Merrimack River, Massachusetts. Transactions of the American Fisheries Society 122: 1088-1103. Krebs, C. J. 1989. Ecological Methodology. Harper and Row, New York, NY. 654pp. Kynard, B. 1997. Life history, latitudinal patterns, and status of shortnose sturgeon, Acipenser brevirostrum. Environmental Biology of Fishes 48: 319-334. LeCroy, S. E. 2000. An illustrated identification guide to the nearshore marine and estuarine gammaridean Amphipoda of Florida: volumes 1 and 2. Annual Report to the Florida Department of Environmnetal Protection, Tallahassee, Florida. 195pp. Lepage, M., and E. Rochard. 1995. Threatened fishes of the world: Acipenser sturio Linnaeus, 1758 (Acipenseridae). Environmental Biology of Fishes 43: 28. Marchetti, M. P., and P. B. Moyle. 2001. Effects of low flow regime on fish assemblages in a regulated California stream. Ecological Applications 11(2): 530-539. Mason W.T. 1991. A survey of benthic invertebrates in the Suwannee River, Florida. Environmental Monitoring and Assessment 16: 163-187. Mason, W. T., and J. P. Clugston. 1993. Foods of the Gulf sturgeon in the Suwannee River, Florida. Transactions of the American Fisheries Society 122: 378-385. McCabe, G. T., R. L. Emmett, and S. A. Hinton. 1993. Feeding ecology of juvenile white sturgeon (Acipenser transmontanus) in the Lower Columbia River. Northwest Science 67(3): 170-180. McCune, B., and M. J. Mefford. 1999. PC-ORD. Multivariate Analysis of Ecological Data, Version 4. MjM Software Design, Gleneden Beach, Oregon. McKechnie, R. J., and R. B. Fenner. 1971. Food habits of white sturgeon. Acipenser transmontanuus, in San Pablo and Suisun bays, California. California Fish and Game 57: 209-212. Mensies, R. J., and D. Frankenberg. 1966. Handbook on the common isopod Crustacea of Georgia. University of Georgia, Athens, GA. 93pp. MjM Software Design. 1999. PC-ORD: Multivariate Analysis of Ecological Data: version 4. Gleneden Beach, Oregon. Moser, M. L., and S. W. Ross. 1995. Habitat use and movements of shortnose and Atlantic sturgeons in the Lower Cape Fear River, North Carolina. Transactions of the American Fisheries Society 124: 225-234.

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109 Wooley, C. M., and E. J. Crateau. 1983. Biology, population estimates, and movement of native and introduced striped bass, Apalachicola River, Florida. North American Journal of Fisheries Management 3: 383-394. Wooley, C. M., and E. J. Crateau. 1985. Movement, microhabitat, exploitation, and management of Gulf of Mexico sturgeon, Apalachicola River, Florida. North American Journal of Fisheries Management 5: 590-605. Worton, B. J. 1989. Kernel methods for estimating the utilization distribution in home-range studies. Ecology 70(1): 164-168. Yako, L. A., M. E. Mather, and F. Juanes. 2002. Mechanisms for migration of anadromous herring: an ecological basis for effective conservation. Ecological Applications 12(2): 521-534. Ysebaert, T., and P. M. J. Herman. 2002. Spatial and temporal variation in benthic macrofauna and relationships with environmental variables in an estuarine, intertidal soft-sediment environment. Marine Ecology Progress Series 244: 105-124. Zar, J. H. 1999. Biostatistical Analysis, 4 th ed. Prentice-Hall, Upper Saddle River, NJ. 663pp.

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BIOGRAPHICAL SKETCH Julianne E. Harris was born on September 21, 1978, in Washington, D.C., and grew up in the great city of Philadelphia, PA. She graduated from Tufts University, Medford, MA, with a Bachelor of Science in 2001. 110


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Title: Distribution of Gulf of Mexico Sturgeon (Acipenser oxyrinchus desotoi) in relation to environmental parameters and the distribution of benthic invertebrates in the Suwannee River Esturary, Florida
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Material Information

Title: Distribution of Gulf of Mexico Sturgeon (Acipenser oxyrinchus desotoi) in relation to environmental parameters and the distribution of benthic invertebrates in the Suwannee River Esturary, Florida
Physical Description: Mixed Material
Creator: Harris, Julianne E. ( Author, Primary )
Publication Date: 2003
Copyright Date: 2003

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DISTRIBUTION OF GULF OF MEXICO STURGEON (Acipenser oxyrinchus desotoi)
IN RELATION TO ENVIRONMENTAL PARAMETERS AND THE DISTRIBUTION
OF BENTHIC INVERTEBRATES IN THE SUWANNEE RIVER ESTUARY,
FLORIDA















By

JULIANNE E. HARRIS


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA


2003

































Copyright 2003

by

Julianne E. Harris



































To my parents.















ACKNOWLEDGMENTS

I thank my advisor, Dr. Daryl Parkyn, for his help and support. I am very thankful

for the opportunity to complete this project with his guidance. I also thank the other

members of my committee, cochair Dr. William Lindberg, and members Drs. Debra

Murie and Edward Phlips, for their input and advice during all stages of this thesis. In

addition, I thank Dr. Kenneth Portier and Mr. Gary Warren for statistical advice and Mr.

Roger Portell, Mr. John Slapcinsky and Ms. Sandra Farrington for help with invertebrate

identification.

Special thanks go to everyone who provided field assistance for this project,

including Carla Beals, Mark Butler, Doug Colle, Jaclyn Debicella, Jason Hale, Jamie

Holloway, Aaron Hunt Branch, Stephen Larsen, Doug Marcinek, Troy Thompson, and

Paul Rebaut.

Funding for this project was provided by the Sturgeon Conservation Initiative

Grant (DJM and DCP), administered by the Florida Marine Research Institute, St.

Petersburg, Florida, and the University of Florida.

I am grateful for the love and support of my family and friends. Their continued

affection and patience have helped me to complete this project. I especially thank my

parents, Edward and Kathleen Pereles, and Ronald and Joan Harris, for their support and

motivation. I also thank my brother, David, and my sisters, Jennifer and Jessica, for

reminding me what is really important and for making me laugh. I also express my

appreciation to Patrick for his constant love, patience, and understanding.
















TABLE OF CONTENTS

page

A C K N O W L E D G M E N T S ......... .................................................................................... iv

LIST OF TABLES ................... ..... ....... ......... ............. vi

LIST OF FIGURES ......... ......................... ...... ........ ............ ix

ABSTRACT .............. ..................... .......... .............. xii

CHAPTER

1 IN TRODU CTION ................................................. ...... .................

2 M ATERIALS AND M ETHOD S ........................................ ......................... 10

Distribution of Relocated Gulf of M exico Sturgeon ................................................10
Distribution of Benthic Invertebrates and Sediment Types............................... 13
Benthic Invertebrate and Sediment Laboratory Analysis........................................14
Relocations of Gulf Sturgeon in Relation to Environmental Parameters and
Benthic Invertebrate D distribution ........................................ ....... ............... 16


3 R E S U L T S .......................................................................... 2 5

Distribution of Relocated Gulf Sturgeon.................. ... ................................25
Distribution of Benthic Invertebrates and Sediment Types............................... 27
Relocations of Gulf Sturgeon in Relation to Environmental Parameters and
Benthic Invertebrate D distribution ........................................ ....... ............... 28
Environm ental Param eters........................................................ ............... 28
Invertebrate D distribution .................... ...... ................... ............... ....30
Environmental Parameters and Benthic Invertebrate Distribution......................32

4 D ISC U S SIO N .......... ......... ................................................................. ......93

L IST O F R EFER EN C E S ......... ................................................................ ............... 103

BIOGRA PH ICAL SKETCH ............... ............. ............................... ............... 110





v















LIST OF TABLES


Table p

1 Sex, size, and sexual maturity at the time of capture for each Gulf sturgeon
surgically implanted with an ultrasonic-tag .................................. ............... 20

2 Dates of tracking surveys of Gulf sturgeon in the Suwannee River estuary,
Florida, and other locations along the central Gulf coast of Florida...................21

3 Duration of residency in the Suwannee River estuary by each ultrasonic-tagged
Gulf sturgeon during the study period from November 2001 through May 2002 ...36

4 Mean and first standard deviation of each sediment size type collected from 28
benthic core location sites in the Suwannee River estuary, Florida.......................37

5 Density in abundance and biomass of all invertebrates, excluding polychaetes,
collected from benthic core sites in the Suwannee River estuary, Florida ..............38

6 Comparisons between the core and petite ponar grab methods for the collection
of invertebrates in the Suwannee River estuary, Florida .....................................39

7 Spearman Rank Correlations (p) between relocation positions of Gulf sturgeon
in the fall of 2001 and environmental parameters collected from the Suwannee
R iver estuary, F lorida ........... ...................................................... .. .... ........40

8 Spearman Rank Correlations (p) between relocation positions of Gulf sturgeon
in the spring of 2002 and environmental parameters collected from the
Suw annee River estuary, Florida ........................................ ......................... 41

9 Cluster number and percentage of each sediment size type at each of the 28
benthic core sites collected in the Suwannee River estuary, Florida .....................42

10 Area within each sediment cluster compared to the frequency of relocations of
G ulf sturgeon w within that cluster ..............................................................................43

11 Spearman Rank Correlations (o) between relocation positions of Gulf sturgeon
in the fall of 2001 and the abundance and biomass of all invertebrate genera
(excluding polychaetes) collected in the Suwannee River estuary, Florida.............44









12 Spearman Rank Correlations (p) between relocation positions of Gulf sturgeon
in the spring of 2002 and the abundance and biomass of all invertebrate genera
(excluding polychaetes) collected in the Suwannee River estuary, Florida.............45

13 Cluster number and total invertebrate biomass (excluding polychaetes) at each
benthic core site collected from the Suwannee River estuary, Florida, ...................46

14 Area within each total invertebrate biomass cluster compared to the frequency of
relocations of Gulf sturgeon within that cluster.....................................................47

15 Cluster number and numerical abundance of major prey resources: amphipods,
brachiopods, and brittle stars, at each of the 28 benthic core sites collected in
the Suw annee River estuary, Florida................................. ......................... 48

16 Area within each prey abundance cluster compared to the frequency of
relocations of Gulf sturgeon within that cluster..................................................49

17 Cluster number and total biomass of main prey resources: amphipods,
brachiopods, and brittle stars, at each of the 28 benthic core sites collected
from the Suwannee River estuary, Florida.................................... ............... 50

18 Area within each prey biomass cluster compared to the frequency of relocations
of Gulf sturgeon w within that cluster....................................................................... 51

19 Cluster number and abundance of brachiopods at each of the 28 benthic core
sites collected in the Suwannee River estuary, Florida......................................... 52

20 Area within each brachiopod abundance cluster compared to the frequency of
relocations of Gulf sturgeon within that cluster..................................................53

21 Cluster number and biomass of brachiopods at each of the 28 benthic core sites
collected in the Suwannee River estuary, Florida............... ................ .............54

22 Area within each brachiopod biomass cluster compared to the frequency of
relocations of Gulf sturgeon within that cluster..................................................55

23 Results of canonical correspondence analysis for benthic invertebrate genera
collected from 28 core sites in the Suwannee River estuary, Florida ....................56

24 Intraset correlations between the environmental variables examined and the
first three axes in the canonical correspondence analysis using invertebrate
genera collected from 28 core sites in the Suwannee River estuary, Florida...........57

25 Final scores by genera from the canonical correspondence analysis.....................58

26 Results of canonical correspondence analysis for benthic invertebrate families
collected from 28 core sites in the Suwannee River estuary, Florida ....................59











27 Intraset correlations between the environmental variables examined and the
three axes in the canonical correspondence analysis using invertebrate families
collected from 28 core sites in the Suwannee River estuary, Florida ....................60

28 Final scores by family from the canonical correspondence analysis .....................61















LIST OF FIGURES


Figure page

1 Study area on the Gulf coast of Florida delineated into tracking areas.................22

2 Benthic core sites in the Suwannee River estuary, Florida, depicted within the
boundary of the M ain Suwannee tracking area.....................................................23

3 C ore collection diagram ................................................ ............................... 24

4 Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee
River estuary, Florida, during the fall of 2001 and the spring of 2002 ..................62

5 Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee
River estuary, Florida, during the fall of 2001 ............................ ............... 63

6 Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee
River estuary, Florida, during the spring of 2002 ........................................ 64

7 Patterns of relocations of Gulf sturgeon in the Suwannee River estuary during
the fall of 2001 and the spring of 2002 calculated as utilization distributions.........65

8 Relocation positions for two individual tagged Gulf sturgeon, Fish F and Fish M, in
the Suw annee River estuary, Florida.............. ................. ................................. 66

9 Relocation positions for Fish G in the Suwannee River estuary, Florida ................67

10 Relocation positions for Fish H in the Suwannee River estuary, Florida ................68

11 Relocation positions for Fish C in the Suwannee River estuary, Florida ................69

12 Relocation positions for Fish Q in the Suwannee River estuary, Florida ...............70

13 Patterns of relocations of tagged Gulf sturgeon in the Suwannee River
estuary during the fall of 2001 calculated as utilization distributions....................71

14 Patterns of relocations of Gulf sturgeon in the Suwannee River estuary during
the spring of 2002 calculated as utilization distributions..................................72

15 Total relative abundance of all invertebrate taxa by phylum, except annelids,
from all 28 cores collected in the Suwannee River estuary, Florida......................73









16 Total relative biomass of all invertebrate taxa by phylum, except annelids,
from all 28 cores collected in the Suwannee River estuary, Florida......................74

17 Temperature and salinity at relocation positions of Gulf sturgeon in the
Suw annee River estuary. ............................................... ............................... 75

18 Percent sediment size type clustered by benthic core site................... .......... 76

19 Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the fall
of 2001 and spring of 2002 in relation to sediment type from 28 core sites in the
Suw annee R iver estuary ................................................ ............................... 77

20 Total biomass of all invertebrates (excluding polychaetes) clustered by benthic
co re site ............................................................................. 7 8

21 Relocations of all Gulf sturgeon in the Suwannee River estuary, Florida, in the
fall of 2001 and spring of 2002 in relation to total invertebrate biomass from
28 core sites in the Suwannee River estuary ............. ...............................................79

22 Numerical abundance of the Gulf sturgeon's main prey resources:
amphipods, brachiopods, and brittle stars, clustered by benthic core site ...............80

23 Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the
fall of 2001 and the spring of 2002 in relation to the abundance of their
main prey resources collected from 28 core sites in the Suwannee River estuary...81

24 Total biomass of the Gulf sturgeon's main prey resources as seen in stomach
contents: amphipods, brachiopods, and brittle stars, clustered by benthic core
site .................................................................................8 2

25 Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the
fall of 2001 and spring of 2002 in relation to the total biomass of their main
prey resources collected from 28 core sites in the Suwannee River estuary............ 83

26 Abundance of brachiopods clustered by benthic core site ................. ................84

27 Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the
fall of 2001 and spring of 2002 in relation to brachiopod abundance collected
from 28 core sites in the Suwannee River estuary .........................................85

28 The distribution of ultrasonic-tagged Gulf sturgeon in relation to the
distribution of brachiopods (abundance/m2) in the Suwannee River estuary ..........86

29 Biomass of brachiopods clustered by benthic core site ............... .......... 8.....87

30 Relocations of Gulf sturgeon in the Suwannee River estuary, Florida, in the
fall of 2001 and the spring of 2002 in relation to brachiopod biomass collected
from 28 core sites in the Suwannee River estuary .........................................88









31 The distribution of ultrasonic-tagged Gulf sturgeon in relation to the
distribution of brachiopods (biomass/m2) in the Suwannee River estuary ..............89

32 Biplot of the canonical correspondence analysis of invertebrate genera and
relocations of Gulf sturgeon by season, by environmental parameters (CCA
axes 1 and 2, represented) ............................................. .............................. 90

33 Biplot of the canonical correspondence analysis of invertebrate genera and
relocations of Gulf sturgeon by season, by environmental parameters (CCA
axes 1 and 3, represented) ............................................. .............................. 91

34 Biplot of the canonical correspondence analysis of invertebrate families and
relocations of Gulf sturgeon by season, by environmental parameters (CCA
axes 1 and 2, represented) ............................................. .............................. 92

35 Locations of two non-tagged Gulf sturgeon observed jumping in the Offshore
tracking area on M arch 8, 2002.................................... ........................... ......... 102















Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

DISTRIBUTION OF GULF OF MEXICO STURGEON (Acipenser oxyrinchus desotoi)
IN RELATION TO ENVIRONMENTAL PARAMETERS AND THE DISTRIBUTION
OF BENTHIC INVERTEBRATES IN THE SUWANNEE RIVER ESTUARY,
FLORIDA

By

Julianne E. Harris

August 2003

Chair: Daryl C. Parkyn
Cochair: William J. Lindberg
Major Department: Fisheries and Aquatic Sciences

Gulf of Mexico sturgeon, Acipenser oxyrinchus desotoi, inhabit the Suwannee

River, Florida, from late spring through early fall before migrating into the Suwannee

River estuary and nearshore Gulf of Mexico. Despite this long river residence, it has

been suggested that Gulf sturgeon forage almost exclusively while in marine and

estuarine environments. The primary goal of the present study was to examine the

distribution of ultrasonic-tagged Gulf sturgeon in the Suwannee River estuary, Florida, in

relation to water quality parameters (salinity, temperature, and dissolved oxygen),

sediment type, and the distribution of benthic invertebrates, especially the distribution of

the Gulf sturgeon's main prey resources: amphipods, brachiopods, and brittle stars.

Ultrasonic-tagged Gulf sturgeon were tracked on emigration from the Suwannee River in

the fall of 2001 until they returned to the river in the spring of 2002. Water quality

parameters were recorded at each relocation position. Patterns of use of the Suwannee









River estuary by the relocated Gulf sturgeon were calculated as utilization distributions.

Sediment and invertebrates were collected from 28 locations in the Suwannee River

estuary. Twelve of the eighteen tagged Gulf sturgeon were relocated at least once in the

Suwannee River estuary from November 7 through December 19, 2001, and then not

again until March 14 through April 17, 2002, for a total of 39 relocations. Relocations of

Gulf sturgeon were associated with areas comprised mostly of sand and containing high

abundances of their main prey resources: amphipods, brachiopods, and brittle stars,

especially brachiopods, the dominant organism observed in stomach contents. Canonical

correspondence analysis and examination of temperature and salinity at relocation

positions of Gulf sturgeon during the fall of 2001 and spring of 2002 suggested

differential use of the Suwannee River estuary during the two different seasons. In the

fall of 2001, relocations of Gulf sturgeon were more associated with offshore areas

characterized by higher salinity and lower temperature than were relocations in the spring

2002. The association between Gulf sturgeon and their main prey resources indicates that

areas within the Suwannee River estuary may be critical foraging habitat for Gulf

sturgeon and that any degradation of the benthos in these areas may pose future risks for

the recovery of this threatened species.














CHAPTER 1
INTRODUCTION

The Gulf sturgeon, Acipenser oxyrinchus desotoi, is an anadromous fish that

seasonally inhabits rivers and coastal areas in the Gulf of Mexico. Historically, Gulf

sturgeon spawned in rivers from Louisiana to Charlotte Harbor, Florida (Fox et al. 2000);

however, habitat changes, pollution, and overfishing have severely reduced populations

and restricted their distribution (Carr et al. 1996). At present, Gulf sturgeon are found

only in systems from east of the Mississippi River to the Suwannee River, Florida (Fox et

al. 2000). The Suwannee River in northwest Florida is thought to have the largest and

most viable population (Foster and Clugston 1997) with an estimated population size of

5,500 sub-adult and adult fish (Pine et al. 2001).

The commercial fishery of Gulf sturgeon began in Tampa Bay in 1886. However,

the fishery was abandoned four years later because insufficient numbers of fish were

caught. In 1896, the fishery resumed near the mouth of the Suwannee River (Huff 1975).

The Apalachicola River also supported a Gulf sturgeon fishery, which effectively ended

in 1970 when only five fish were caught (Wooley and Crateau 1985). While it is known

that commercial fisheries for Gulf sturgeon existed in other rivers along the Gulf of

Mexico, documentation of the history of these fisheries is scant. In Florida, Gulf

sturgeon sustained substantial commercial and limited sport fisheries (Fox et al. 2000);

however, population declines led to the closure of all fisheries in 1984 in the state (Carr

et al. 1996). In 1991, the Gulf sturgeon was listed as a threatened species under the

Endangered Species Act of 1973 (Carr et al. 1996). To increase populations, the United









States Fish and Wildlife Service (USFWS) and the Gulf States Marine Fisheries

Commission (GSMFC) worked together to complete a Recovery/Fishery Management

Plan for the Gulf sturgeon calling for more information to be collected on natural history

and habitat requirements for the species (Fox et al. 2000). One critical component of the

Gulf Sturgeon Recovery/Fishery Management Plan was the identification of critical

estuarine and marine habitats for the Gulf of Mexico sturgeon (USFWS et al. 1995). In

August of 2001, a landmark court decision mandated that the Federal Government define

and protect essential fish habitat (EFH) for Gulf of Mexico sturgeon. Areas of critical

habitat were to be defined by February of 2003 (USFW and NMFS).

Ecological research on Gulf sturgeon has focused mostly on river use and has

concentrated on river systems in Florida, especially the Suwannee River because the

Suwannee is thought to have the largest and most viable population of Gulf sturgeon

(Pine et al. 2001). Gulf sturgeon migrate into the Suwannee River between late February

and early July when surface temperatures in the river have risen to an average of 22.1 C

(Foster and Clugston 1997). Chapman and Carr (1995) observed Gulf sturgeon entering

the river at slightly lower temperatures (peak temperature at entrance averaged 17.2 C)

and that this immigration occurred with incoming tides when temperature differences

between the Gulf of Mexico and the Suwannee River were at a minimum (about 1-2 C

difference). The observed difference between the two studies, with respect to river

temperature during migration, may be a result of differences in depth where temperature

measurements were collected in the water column. By late July, fish begin to congregate

in the river near springs where they will stay for the summer (Foster and Clugston 1997).

Gulf sturgeon spawn in the upper areas of the river in March and April (Sulak and









Clugston 1998, 1999). Non-spawning fish also enter the river (Huff 1975, Chapman and

Carr 1995) for reasons that are not yet fully understood. It has been hypothesized that

Gulf sturgeon reside in the Suwannee River from late spring to mid-fall because the river

waters are cool, due to numerous springs (Chapman and Carr 1995, Carr et al. 1996,

Foster and Clugston 1997). Gulf sturgeon remain in the Suwannee River until late

August to early December (Foster and Clugston 1997), when they migrate down river and

enter the Gulf of Mexico (Smith and Clugston 1997). It has been suggested that this

migration may be initiated by a decrease in temperature (Wooley and Crateau 1985,

Chapman and Carr 1995, Foster and Clugston 1997).

The role of temperature in the migration from riverine to estuarine environments

has been observed in another Gulf of Mexico species, the Gulf striped bass, Morone

saxatilis. Like Gulf sturgeon, Gulf striped bass have been extirpated from many of the

coastal river systems where populations previously existed. They originally ranged from

Lake Pontchartrain, Louisiana, to the Suwannee River, Florida (Wooley and Crateau

1983). Gulf striped bass remain in rivers through the summer, taking advantage of the

cool refuge provided by the springs. A mark and re-capture study has shown that

significant weight loss occurred while the fish were in the river, suggesting that metabolic

needs were higher, feeding was reduced, or both (Wooley and Crateau 1983).

Temperature has been suggested to play an important role in the timing of migration of

other anadromous species including sockeye salmon, Oncorhychus nerka (Hodgson and

Quinn 2002), and brown trout, Salmo trutta (Jonsson and Jonsson 2002).

Patterns of use of estuarine and nearshore marine habitat by Gulf sturgeon in the

Choctawhatchee Bay system suggested that most sturgeon remained in the nearshore









waters of the Choctawatchee Bay on substrates that were predominantly composed of

sand and in depths of usually 2-4 m (Fox et al. 2002). Fox et al. (2002) located three

tagged fish in fully marine waters of the Gulf of Mexico and hypothesized that nine of the

twenty tagged fish migrated from the Choctawatchee Bay into the Gulf for a period of at

least six weeks. Less research has been conducted on estuarine and marine habitat use by

Gulf sturgeon in the Suwannee River system. Sulak and Clugston (1999) tracked six

tagged sturgeon continuously for periods up to three days in the Suwannee River estuary

and found that the tagged fish remained in nearshore waters, 5-10 m deep, from October

through mid-December. In another study, tagged sturgeon were observed to reside

outside the Suwannee River, in the Suwannee Sound, for 2-4 weeks before leaving the

area (Carr et al. 1996).

Current thought is that Gulf sturgeon forage almost exclusively in estuarine and

Gulf waters (Huff 1975, Wooley and Crateau 1985, Mason and Clugston 1993, Gu et al.

2001). While some Gulf sturgeon stomachs contained prey when they entered the

Suwannee River from the adjacent estuary, they were empty in higher areas of the river

(Mason and Clugston 1993). This suggests that the fish did not eat while in the river.

Also, Gulf sturgeon had higher length to weight ratios after they spent the summer in the

Suwannee River than just before they entered the Suwannee River in the spring, which

may have been caused by fasting, but may also have been a result of a change in

reproductive status (Huff 1975). Similarly, a mark and recapture study in the

Apalachicola River, Florida, found that individual Gulf sturgeon lost about 4-15% of

their body weights while in the river (Wooley and Crateau 1985). In addition, the

average and range of carbon-13 ratios for adult and sub-adult Gulf of Mexico sturgeon









were more consistent with the signatures of biota and sediment organic matter from the

Gulf of Mexico than with signatures of benthic organisms collected in the Suwannee

River (Gu et al. 2001). These studies support the idea that sturgeon feed almost

exclusively in estuarine/marine waters and little in rivers. However, Gulf sturgeon in

Choctawatchee Bay were typically found in areas with low invertebrate densities (Fox et

al. 2002). The authors hypothesized that Gulf sturgeon in this system may forage

primarily on specific invertebrates that could not be collected by their sampling gear,

such as the ghost shrimp, Lepidophthalmus louisianensis, and the snapping shrimp,

Leptalpheusforcepts (Fox et al. 2002).

Similar studies on foraging behavior and the use of estuarine and marine

environments have been conducted on other Acipenser species. The white sturgeon, A.

transmontanus, is anadromous in some river systems. Many anadromous white sturgeon

live and feed in estuaries (McKechnie and Fenner 1971, Muir et al. 1988), especially near

shallow water areas where benthic prey resources are plentiful (McKechnie and Fenner

1971). In the Columbia River system, white sturgeon stomach contents revealed that

juveniles primarily consumed the amphipod, Corophium salmonis, while larger

individuals preyed more heavily upon marine fish, especially the northern anchovy,

Engraulis mordax (Muir et al. 1988, McCabe et al. 1993). In contrast, white sturgeon in

San Pablo and Suisun Bays, California, consumed mostly clams (McKechnie and Fenner

1971). Because of the wide variety of prey resources consumed by white sturgeon, it is

probable that this species is an opportunistic forager. The relationship between specific

prey densities and juvenile white sturgeon densities in the Columbia River was poor.

Authors suggested that white sturgeon may migrate to the estuary to forage, or may









simply be feeding very efficiently in the river (McCabe et al. 1993). More studies need

to be conducted to determine where these sturgeon are specifically foraging.

Lake sturgeon, A. fulvescens, is a potadromous species inhabiting lake and river

environments. Lake sturgeon in the Moose River drainage, Ontario, appeared to be

generalists, feeding upon macroinvertbrates, especially the burrowing mayfly, Hexagenia

sp. (Chiasson et al. 1997, Beamish et al. 1998). In Lake Winnebago, Wisconsin, lake

sturgeon were observed to forage primarily upon baetid nymphs (0. Ephemeroptera) and

dipteran larvae (Kempinger 1996). Juvenile lake sturgeon were observed to be in highest

densities in areas where known prey species were found in only moderate density

(Chiasson et al. 1997, Rusak and Mosindy 1997). However, lake sturgeon were found

more often in areas with clay substrates, as were the benthic invertebrates that they

consumed (Chiasson et al. 1997, Beamish et al. 1998).

The green sturgeon, A. medirostris, is an anadromous species of the North Pacific.

Little is known about the life history of this species (Scott and Crossman 1973, Erickson

et al. 2002); however, it is thought that green sturgeon forage in the estuarine mouths of

large rivers (Scott and Crossman 1973, Erickson et al. 2002). One account of the food

habits of seventy-five individuals from Kyuoquat Sound, British Columbia, found that

the sturgeon had been eating sand lance, Ammodytes hexapterus (Hart 1973), a fish that

buries in the sand.

The movements of shortnose sturgeon, A. brevirostrum, are complex and differ

depending upon river system and latitude. More northern populations (e.g., Maine and

New Brunswick) spend most of their time in brackish or marine waters. Adults leave the

estuaries from June until August to forage in the rivers when the rivers' temperatures are









at their highest. More centrally-distributed shortnose sturgeon (e.g., Massachusetts to

Delaware) use marine waters the least, entering for only a very short period of time.

Populations in the more southern portion of the sturgeon's distribution (e.g., North

Carolina and Georgia) enter marine waters during the winter and forage either in or just

upstream of the saltwater/freshwater interface. Water temperature differences are

hypothesized to cause this change in behavior (Kynard 1997). In many systems,

shortnose sturgeon appear to have very specific areas of the river and estuary where they

spawn, forage, overwinter, and rest. Shortnose sturgeon migrate to and from these areas

over the course of the year (Bain 1997, Hall et al. 1991, Buckely and Kynard 1985,

Hastings et al. 1987). Juvenile shortnose sturgeon in the Saint John River Estuary, New

Brunswick, eat primarily insects and crustaceans, while adults eat mostly molluscs

(Dadswell 1979). Shortnose sturgeon in the Hudson River Estuary were observed to eat

soft-bodied invertebrates, including amphipods, chironomids, and isopods (Haley 1998).

The closest relatives to the Gulf sturgeon are the Atlantic sturgeon, A. o.

oxyrinchus, and the European sturgeon, A. sturio (Artyukhin and Vecsei 1999). These

two species spend most of the year in estuarine and marine environments and usually

enter freshwater only to spawn. Spawning occurs for European sturgeon in May and

June (Lepage and Rochard 1995). Atlantic sturgeon spawn following the latitudinal

pattern of February and March in more southern rivers, April and May in centrally

located rivers, and May through July in Canadian rivers (Smith and Clugston 1997).

Before migrating to the ocean, juvenile European sturgeon congregate in prey-rich

regions of the Gironde River Estuary, France, possibly to feed on polychaetes, their main

prey resource (Brosse et al. 2000, Taverny et al. 2002). Populations of Atlantic sturgeon









in New York, Massachusetts, and South Carolina appear to spend most of the year in an

estuary or the Atlantic ocean and may only move up river to spawn (Dovel and Berggren

1983, Kieffer and Kynard 1993, Collins et al. 2000). In the Hudson River Estuary,

juvenile Atlantic sturgeon were observed to forage on polychaetes, isopods, and

amphipods (Haley 1998). Observations of feeding habits off the coast of New Jersey

determined that Atlantic sturgeon ate during the spring and fall, however, a larger

proportion of empty stomachs were observed in the spring. Atlantic sturgeon in this

system primarily foraged on polychaetes followed by isopods, decapods, and amphipods.

Authors noted that there were differences in the relative importance of different prey

types between the two seasons (Johnson et al. 1997).

Despite available food resources (Mason 1991), adult Gulf sturgeon appear to

forage little in the Suwannee River. Mason and Clugston (1993) found that stomach

contents from adult sturgeon entering the Suwannee River contained nearshore coastal

shelf organisms including: lancelets, Branchiostoma caribaeum, brachiopods,

unidentified pelagic shrimps, polychaetes, molluscs, starfish, and sea cucumbers (Mason

and Clugston 1993). Carr et al. (1996) examined 157 adult Suwannee River Gulf

sturgeon and found that 32% of stomachs contained exclusively brachiopods and ghost

shrimp and 11% contained lancelets, echinoderms, and bivalves. From 2000-2002,

stomach contents collected from Gulf sturgeon entering the Suwannee River from the

estuary contained: 69% brachiopods, 24% amphipods, 2% brittle stars and 5% other

organisms such as isopods, sea cucumbers, shrimp, and polychaetes (Murie and Parkyn

2002).









The primary goal of this study was to examine the distribution of the Gulf of

Mexico sturgeon in relation to the distribution of their prey resources in the Suwannee

River estuary and adjacent nearshore regions of the Gulf of Mexico. The specific

objectives were: 1) to track sonically-tagged Gulf sturgeon in the Suwannee River estuary

and nearshore Gulf of Mexico; 2) to determine the distributions of benthic invertebrate

species in the Suwannee River estuary; and 3) to examine the relationship between

relocations of Gulf sturgeon, specific prey resource densities, and environmental

parameters in the Suwannee River estuary.














CHAPTER 2
MATERIALS AND METHODS

Distribution of Relocated Gulf of Mexico Sturgeon

Eighteen adult Gulf of Mexico sturgeon, six females and twelve males, were caught

using gill nets at the mouth of the Suwannee River (East Pass) during their upstream

migration between February and April, 2001, as part of a study addressing the effects of

broodstock collection on mortality of net captured sturgeon (Parkyn et al. unpublished

data). Each Gulf sturgeon was surgically implanted with a high power ultrasonic tag

(Chp 87-L, Sonotronics Tucson, AZ). Size and reproductive status of each ultrasonic

tagged Gulf sturgeon is presented in Table 1. Tags operated at a frequency of 73 to 78

kHz, which is optimal for use in both freshwater and marine environments (Sonotronics,

personal communication) and could be heard from distances of 1-3 km, depending upon

salinity, tag strength, and bathymetry. Each tag had its own unique pulse pattern

facilitating the identification of individual fish relocated during the study period.

Tracking for the present study began as tagged Gulf sturgeon left the Suwannee

River in the fall of 2001 and continued until the fish re-entered the Suwannee River in the

spring of 2002. The majority of tracking took place within 7 km of the coastline outside

the Suwannee River; however, tracking surveys were also conducted farther offshore and

in estuarine areas outside Cedar Key, Waccasassa River, and Crystal River, Florida

(Figure 1). Tracking surveys were conducted on 48 different days during this period: five

in November, six in December, ten in January, six in February, ten in March, and eleven

in April (Table 2). Individual fish were located by tracking along transects oriented









parallel to the coastline and typically less than 1.85 km (1 nautical mile) apart to ensure

that all tagged sturgeon between transects would be located.

Gulf sturgeon were located along transects using an omni-directional ultrasonic

hydrophone (DH3, Sonotronics, Tucson, AZ) and receiver (USR-96, Sonotronics,

Tucson, AZ), which receives sonic pulses from the ultrasonic tags earlier implanted

inside the sturgeon. Once a signal was received with the omni-directional hydrophone, a

directional hydrophone (dh-1, Sonotronics, Tucson, AZ), Global Positioning Satellite

receiver (GPS)(Garmin GPS 12, Olathe, KS), and compass (Silva Ranger, Livingston,

Great Britain) were used to triangulate the fish's position. Temperature, dissolved

oxygen, and salinity were measured 10 cm above the bottom using a YSI 85 meter

(Yellow Springs Instrument Corp., Yellow Springs, AZ).

To determine if relocations of Gulf sturgeon were uniform, random, or aggregated

in their distribution, a Clark and Evans nearest neighbor index of aggregation test was

used (Krebs 1989). Area within the Main Suwannee tracking area (MSTA) (Figure 1)

and distances between relocation positions of sturgeon were calculated using ArcView

3.2 (ESRI 1999). Points representing all individual relocations of Gulf sturgeon in the

MSTA of the estuary were included in the analysis to increase sample size; however, if a

sturgeon was followed or otherwise relocated more than once during the same day, only

the first relocation for the day was included to standardize for effort. The first relocation

of a given fish on a given day was used in this and all subsequent analyses in this study.

Patterns of use of the Suwannee River estuary by the tagged Gulf sturgeon were

examined using a kernel method. Kernel methods produce non-parametric estimations of

an animal's utilization distribution (UD), which is defined as the distribution of an









animal's positions in a plane (Worton 1989). Utilization distributions of 50%, 80%, and

95% (the smaller the percentage, the more highly used the area is) were calculated using

the Animal Movement SA Version 2.04 extension in ArcView 3.2 (ESRI 1999).

Utilization distributions were calculated using a fixed kernel size and a least-squares

cross-validation choice for the smoothing factor. This method has been shown to

estimate UDs with accuracy, even when sample sizes are low (Worton 1989, Seaman et

al. 1999). This kernel method was applied to relocation positions of Gulf sturgeon during

the entire study period, as well as for relocations in the fall of 2001 and those in the

spring of 2002 separately, for comparison. In the present study, UDs were calculated for

the purpose of examining and displaying use of the Suwannee River estuary by the

tagged Gulf sturgeon during the tracking period, not to estimate home range. Patterns of

use were not examined by minimum convex polygons because they could not be properly

constructed using the sample sizes obtained in this study.

To test the hypothesis that the number of male sturgeon and female sturgeon

relocated during the fall of 2001 and spring of 2002 were equal, a Fisher's exact test was

used (SAS 2000). To test the hypothesis that the interval of time spent in the Suwannee

River estuary by males and females during the spring of 2002 was similar, a Wilcoxon

Rank Sum test was used (Hollander and Wolfe 1999, SAS 2000).

To test the hypotheses that bottom temperature, salinity, and dissolved oxygen, at

sites where sturgeon were relocated during the fall of 2001 and the spring of 2002 were

similar, Student and Satterthwaite t-tests were used (SAS 2000). Satterthwaite t-tests

(SAS 2000, Reed 2003) were used when variances between groups differed (Folded F









test, P < 0.01), but groups did not deviate greatly from normality (Shapiro-Wilk, P >

0.01) (SAS 2000).

Distribution of Benthic Invertebrates and Sediment Types

Benthic cores were collected from 28 locations, between April 22 and May 9, 2002,

to survey the distribution of benthic invertebrates in the Suwannee River estuary (Figure

2). The general area selected for benthic invertebrate examination was the Main

Suwannee tracking area (MSTA) (Figure 1). Twenty-three sample sites were evenly

spaced within the MSTA, one sample site was intended to be part of the evenly spaced

grid, but had to be moved slightly because it was out of the water, and four sample sites

were specifically placed within the MSTA near locations with higher numbers of

relocations of Gulf sturgeon (Figure 2).

Divers collected cores using SCUBA when sites were more than 1.5 m in depth and

snorkel when sites were shallower. Each core was made of a 15.24 cm piece of 10.16 cm

diameter PVC pipe, fitted with two lids. The core, therefore, had a surface area of 81cm2

and a volume of 1234 cm3. At each site, ten cores were collected, two at the center and

two from each of four locations -30.5 m from the center, determined by swimming

bearings of 50, 140, 230, and 320 degrees from the central location. These specific

bearings were chosen because they were parallel to the coastline (Figure 3). Cores

collected from the same site and bearing were pooled as a means of increasing the

volume of material sampled and considered one sample in subsequent examinations.

Temperature, dissolved oxygen, and salinity were measured 10 cm above the bottom, as

described previously for water quality parameters collected at relocations positions of

Gulf sturgeon. Depth at mean low water at each site was determined from the NOAA

navigation chart for the region (Chart 11408, 1998). Distance from each central core









location to the center of the closest entrance to the Suwannee River was measured using

ArcView 3.2 (ESRI 1999). The basemap of the Suwannee River estuary used for this

project was FLSHR (1-8): Florida Shoreline (Florida Department of Environmental

Protection).

In addition to benthic cores, three benthic sub-samples were collected using a petite

ponar grab (400mm2) from six core locations to allow comparisons between the two

collection methods in terms of relative invertebrate abundance and absolute number of

genera collected. The six core sites randomly selected were 3X, 5Y, 7Y, 7Z, 8Y and 9Z

(Figure 2). Both cores and petite ponar grabs were immediately frozen until they could

be processed.

Benthic Invertebrate and Sediment Laboratory Analysis

Sediment from each sample was described using a modified Wentworth scale. To

examine sediment characteristics, one quarter of each core was run through a series of

five sieves: 4 mm, 2 mm, 0.85 mm, 0.25 mm, and 0.125 mm. The percent sediment

captured within each sieve was estimated visually. Sediment groups were named

according to particle size: 'Oyster Shell' (4mm); 'Small Shell' (2mm); 'Coarse Sand'

(0.85mm); 'Medium Sand' (0.25mm); 'Fine Sand' (0.125mm); and 'Silt' (below

0.125mm). Fine Sand and Silt were combined for analysis and called 'Very Fine Sand'

and Coarse Sand and Medium Sand were merged and called 'Sand' to reduce the number

of sediment variables used for analysis. Oyster Shell and Small Shell were not combined

because they were composed of shell from different organisms and could represent very

different habitat types. Sites with high percentages of Oyster Shell were usually part of

or near a living oyster bar composed of the eastern oyster, Crassostrea virginica, whereas

sites with high percentages of Small Shell were not always in areas near oyster bars. All









remaining sediment was run through a 0.85 mm sieve. All invertebrates retained by the

0.85 mm sieve and coarser were collected for enumeration and identification.

All invertebrates collected from a sample were examined immediately after the

sieving process. Invertebrates were sorted, counted, weighed, and then fixed in 5%

phosphate-buffered formalin and saved for later identification. In cases where more than

ten specimens of the same species were found within a sample, groups were sometimes

formed according to size and subsamples of individuals within each size group were

weighed. Total weight for all specimens of each species was later estimated based upon

the known weights of the subsamples. Individuals of some species were also measured

for length and width. All invertebrates were later identified to the lowest taxonomic level

possible using reference keys (Richardson 1905, Thomas 1962, Williams 1964, Menzies

and Frankenberg 1966, Bousfield 1973, Watling 1979, Heard 1982, Williams 1984,

Abele and Kim 1986, Hendler et al. 1995, LeCroy 2000). Polychaetes were not identified

because incompatibility with the collection technique prevented preservation of features

needed for taxonomic identification. Some specimens of each species were permanently

stored in 70% ethanol as a reference collection. Identification of reference specimens

were verified by specialists from the University of Florida Museum of Natural History

and by comparison with voucher identified specimens from the invertebrate collection at

the Florida Marine Research Institute. The reference collection for the present study is

archived at the Department of Fisheries and Aquatic Sciences, University of Florida.

To test the hypothesis that the relative abundances of specific invertebrate groups

collected by the core and petite ponar grab methods, at each of the six sites, were similar,

Fisher's exact tests were used (Zar 1999, SAS 2000). In addition, to test the hypothesis









that the absolute number of genera collected by the two methods at each site was similar,

a Friedman distribution-free randomized complete block design test was used (Hollander

and Wolfe 1999).

Relocations of Gulf Sturgeon in Relation to Environmental Parameters and Benthic
Invertebrate Distribution

To examine correlations between the frequency of relocations of Gulf sturgeon in

the fall of 2001 and those in the spring of 2002, with environmental parameters, and with

the abundance and biomass of specific invertebrate genera, Spearman Rank Correlation

tests were used (Hollander and Wolfe 1999, SAS 2000). Each relocation position of a

Gulf sturgeon was assigned to the nearest benthic core site for these analyses.

Benthic core sites were clustered using the Ward's minimum variance method (PC-

ORD 4, MjM Software Design 1999) according to: sediment size type; total biomass of

all invertebrates (excluding polychaetes); abundance and biomass of the Gulf of Mexico

sturgeon's main prey resources in the Suwannee River estuary as observed in stomach

contents: amphipods, brachiopods, and brittle stars (Murie and Parkyn 2002); and

abundance and biomass of brachiopods, the dominant food resource found in the

stomachs of Gulf sturgeon in the Suwannee River system. Ward's is a hierarchical

clustering method that describes the distance between any two objects as the squared sum

of the distances of each object from the cluster's mean. In each step of the process the

cluster that is formed is the one that results in the smallest increase in the sum of squares

(Tinsley and Brown 2000). Prey abundances were logio(x+l) transformed to reduce the

variation between the three prey groups and brachiopod abundance was loglo(x+l)

transformed to reduce the effect of very high abundances. It was unnecessary to

transform data for any other cluster analyses. Core sites were then projected into an









equal area projection and interpolated to fill the MSTA using the Create Theissen

Polygons extension in ArcView 3.2 (ESRI 1999). In Theissen polygon interpolation, also

known as nearest neighbor interpolation, adjacent areas not sampled are assigned the

value of the closest sample (Bolstad 2002). Interpolated core sites were then grouped

according to their cluster number, and area within each cluster was calculated.

To determine if the frequency of relocations of Gulf sturgeon within each cluster,

compared to the area within each cluster, was similar, Fisher's exact tests were used. The

purpose of these Fisher's exact tests was to determine if relocations of sturgeon were

significantly distributed within the MSTA according to any of the clustered variables:

sediment size type, total invertebrate biomass, abundance and biomass of main prey

resources, and abundance and biomass of brachiopods. To further examine the

distribution of Gulf sturgeon in relation to the abundance and biomass of brachiopods,

brachiopod abundance/m2and biomass/m2 were interpolated using an inverse distance

weighting method and displayed with all relocation positions of Gulf sturgeon during the

fall of 2001 and the spring of 2002 using ArcView 3.2 (ESRI 1999). The inverse

distance weighting method estimates the values of unknown locations using the values

and distances of neighboring points. The farther away a neighboring point is, the less

weight its value will have on defining the value of the unknown location (Bolstad 2002).

Canonical correspondence analyses (CCA)(PC-ORD 4) was used to examine the

distribution of the relocations of Gulf sturgeon in the fall of 2001 and spring of 2002 and

benthic invertebrates, in relation to tested environmental parameters (Ter Braak 1986,

Palmer 1993). CCA is a robust weighted-averaging method that directly ordinates

community data in a fashion consistent with tested environmental variables, therefore,









variation in the distribution of the invertebrates can be explained in terms of the

environmental parameters examined in the study. CCA provides a direct multivariate

analysis, such that gradients within the environmental variables are regressed into the

ordination procedure during each step of the iteration process (Ter Braak 1986, Palmer

1993, Rakocinski et al. 1997). CCA was conducted on invertebrate abundances at both

the genera and the family levels to determine if outcomes between the levels would be

similar (Warwick 1988, Somerfield and Clarke 1995). Genera or families observed at

less than three of the 28 sample sites were removed from analysis to reduce the effects of

rare taxa. Taxa abundances were transformed by logio(y+l) for the analysis to reduce the

effect of absolute abundances. Environmental parameters included four sediment

measures: Oyster Shell, Small Shell, Sand, and Very Fine Sand; as well as three

environmental parameters: Depth, Distance from the closest mouth of the Suwannee

River (DFRM), and Dissolved Oxygen. Because Gulf sturgeon were not relocated at the

specific date or time when environmental parameters were measured for the CCA,

temperature and salinity were excluded from these analyses. Temperature and salinity

were observed to vary greatly depending upon the specific time and date of collection and

therefore may cause bias to the results. Percent data (sediment parameters) were arcsin

transformed (Zar 1999) and directly measured data (all other environmental parameters)

were transformed by logio(x+l) to reduce kurtosis (Griffith et al. 2001, Marchetti and

Moyle 2001, Ysebaert and Herman 2002, Griffith et al. 2003). Intraset correlations are

the correlations between the environmental variables and the ordination axes (Ter Braak

1986). Using intraset correlations is recommended because, in the CCA process,

invertebrates are ordinated according to the tested environmental variables. Thus, the









reader is able to see the direction and magnitude of the relationship between the axes

created and the specific environmental variables tested (Palmer 1993, McCune and

Mefford 1999). However, CCA procedures can inflate intraset correlation values because

the tested environmental parameters themselves constrain the calculation of the

ordination axes. Therefore, it is suggested that the signs and relative magnitudes of the

intraset values be used to examine the relative importance of each environmental variable

in structuring the invertebrate community, not as independent measures of the strength of

the relationships between the specific environmental variables and the invertebrate

community (McCune and Mefford 1999). For descriptive purposes in this study, intraset

values greater than 0.399 were considered more highly correlated than those below 0.399.

This criterion was not intended to reflect statistical significance and all intraset values are

presented for the reader to examine.











Table 1. Sex, size, and sexual maturity at the time of capture for each Gulf sturgeon
surgically implanted with an ultrasonic tag. Gulf sturgeon were captured in
gill nets at the mouth of the Suwannee River from February through April of
2001.


Sex Total Length
(cm)
Male 1496
Male 1613
Male 1345
Male 1279
Male 1450
Male 1540
Male 1375
Male 1484
Male 1476
Male 1406
Male 1622
Male 1473
Female 2010
Female 1922
Female 1869
Female 1798
Female 1846
Female 1768


Fork Length
(cm)
1332
1429
1217
1137
1295
1370
1224
1333
1340
1256
1415
1319
1790
1776
1717
1595
1688
1575


Weight (kg)


19.25
29.25
16.50
15.25
17.25
22.25
16.25
22.50
19.75
18.75
28.75
20.00
53.25
42.25
53.25
46.25
52.75
41.75


Fish
Identifier
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R


Sexually
Mature
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes











Table 2. Dates of tracking surveys of Gulf sturgeon in the Suwannee River estuary,
Florida, and other locations along the central Gulf coast of Florida.
Month Day Year Tracking Area


Main Suwannee
Main Suwannee
Main Suwannee
Main Suwannee and Lower Suwannee
Main Suwannee
Main Suwannee
Main Suwannee
Main Suwannee
Main Suwannee
Main Suwannee and Upper Suwannee
Main Suwannee and Upper Suwannee
Main Suwannee and Offshore
Main Suwannee
Offshore
Offshore
Offshore
Lower Suwannee and Cedar Key
Cedar Key
Waccasassa Bay
Waccasassa Bay
Crystal River Estuary


November 7
November 11
November 18
November 20
November 28
December 2
December 8
December 10
December 15
December 19
December 20
January 5
January 9
January 10
January 11
January 17
January 26
January 27
January 28
January 29
January 31
February 8
February 9
February 12
February 15
February 24
February 28
March 1
March 7
March 8
March 9
March 12
March 13
March 15
March 16
March 17
March 18
April 1
April 2
April 10
April 13
April 14
April 15
April 16
April 17
April 19
April 23
April 26


2001
2001
2001
2001
2001
2001
2001
2001
2001
2001
2001
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002


Offshore
Main Suwannee
Main Suwannee
Main Suwannee and Lower Suwannee
Main Suwannee
Main Suwannee and Lower Suwannee
Main Suwannee
Main Suwannee and Offshore
Offshore
Main Suwannee
Main Suwannee and Offshore
Main Suwannee
Main Suwannee
Main Suwannee and Lower Suwannee
Main Suwannee
Main Suwannee and Upper Suwannee
Main Suwannee
Main Suwannee
Main Suwannee
Main Suwannee
Main Suwannee
Main Suwannee
Main Suwannee
Main Suwannee
Lower Suwannee
Main Suwannee
Main Suwannee and Lower Suwannee



































83010' 82045'


Figure 1. Study area on the Gulf coast of Florida delineated into tracking areas.
Tracking Areas: A-Main Suwannee, B-Lower Suwannee, C-Upper
Suwannee, D-Cedar Key, E-Offshore, F-Waccasassa Bay, G-Crystal
River estuary.




















29020'- ^ 2920'
3Z
4Y 5X .
4Z 5Y
6X

aS2 M7Xi
06 *7Y 8X
S3, $S4
07Z 8Y
29015' a 9X 29015'


0 2 Miles 09Z



83015' 83010' 8305'


Figure 2. Benthic core sites (filled circles) in the Suwannee River estuary, Florida,
depicted within the boundary of the Main Suwannee tracking area. Labels
nearest to each benthic core site represent the specific site identifier. S-sites
were specifically chosen because high numbers of sturgeon were relocated
near those locations. All cores were collected from the Suwannee River
estuary, Florida, from April 22 through May 9, 2002.





















29020' -- 29020





\ ---rr
\ ; \ 5





29015' 29015'




0 6 Miles


83015' 83010' 83O5'





50


320 140




230



Figure 3. Core collection diagram: Cores were collected from the center location,
illustrated on the map, and then four satellite locations 30.5 m from the central
location, by swimming 50, 140, 230, and 320 from the center. All cores
were collected in the Suwannee River estuary, Florida, from April 22 through
May 9, 2002.














CHAPTER 3
RESULTS

Distribution of Relocated Gulf Sturgeon

Thirteen of the eighteen Gulf of Mexico sturgeon tagged in the spring of 2001 were

relocated in the Suwannee River estuary from November 2001, through May 2002, for a

total of 39 relocations in the 48 days of tracking. Tagged sturgeon were relocated in the

estuary in the fall from November 7, 2001, through December 19, 2001, and then again in

the spring from March 14, 2002, through April 17, 2002. However, no Gulf sturgeon

were relocated during the months of January or February 2002. Eight of 18 tagged-

sturgeon, seven males and one female, were relocated in the estuary during the fall of

2001 for durations of one to six days (X + I sd, 2.1 + 2.1 days) (Table 3). During the

spring of 2002, 10 of 18 tagged-sturgeon, five males and five females, were relocated in

the estuary for durations of one to 31 days (8.3 10.8 days) (Table 3). No significant

difference was detected between the number of males found during the fall and spring,

and the number of females found during the fall and spring (Fisher's exact test, n = 2, P =

0.15). In addition, no significant difference was detected between the relocation interval

for males and females during the spring of 2002 (Wilcoxon t-approximation, two sample,

two-sided test, n = 10, W= 23, P = 0.40).

All relocations of tagged sturgeon were made in the Main Suwannee tracking area

(MSTA), except one, which was made in the Lower Suwannee tracking area (Figures 4-

6). Within the MSTA, relocations of Gulf sturgeon were significantly aggregated or

clumped in their distribution (Clark and Evans nearest neighbor index of aggregation test,









n = 38, Z = -3.78, P <0.001). Patterns of relocations of Gulf sturgeon, calculated as

utilization distributions (UD) and including all relocations (n = 39), in the Suwannee

River estuary during the fall of 2001 and the spring of 2002 are illustrated in Figure 7.

The most highly used area, the 50% UD, was situated adjacent to Alligator Pass, one of

the three mouths of the Suwannee River. North of West Pass was also a well used area.

Much of the MSTA appears to be used by Gulf sturgeon during the fall and spring

relocation periods (Figure 7).

Five of the eighteen tagged Gulf sturgeon were relocated in the MSTA during both

the fall of 2001 and the spring of 2002 (Table 3). However, the movements of these five

sturgeon within the MSTA during the fall of 2001 and the spring of 2002 appear

different. Two of the five Gulf sturgeon, Fish F and Fish M, were relocated in one

general area in the fall and in a different area in the spring (Figure 8). In contrast, Fish G

was relocated outside Alligator Pass in both the fall and the spring (Figure 9). Fish H

was relocated only once during the fall of 2001 and was relocated in two distinct areas

during the following spring (Figure 10). In contrast, Fish C moved around the estuary

and was relocated more often than the other tagged fish; it was relocated north of West

Pass during the fall of 2001 and the beginning of the spring of 2002, then moved closer to

Alligator Pass in the later part of the spring of 2002 (Figure 11). Fish Q was relocated in

the estuary on three consecutive days, between Alligator Pass and East Pass, during the

spring of 2002 (Figure 12).

Utilization distributions of relocations of Gulf sturgeon in the fall of 2001 (n = 10),

and the spring of 2002 (n = 28), were both mostly confined to the Main Suwannee

tracking area (Figures 13 and 14). However, the utilization distributions calculated for









the fall, compared to those calculated for the spring, exhibited differences. The observed

area used by sturgeon in the fall of 2001 appears larger than the observed area used in the

spring of 2002 (Figures 13 and 14). Apparent differences may be because relocations of

sturgeon in the fall of 2001 were less frequent (Table 3), farther away from the closest

mouth of the Suwannee River (Paired, two tailed, t-test, t = 1.91 n = 39, P = 0.064), and

more dispersed within the studied area, than relocations were in the spring of 2002. In

addition, the most highly used area, the 50% UD, in the spring of 2002, was outside

Alligator Pass, whereas in the fall of 2001, the most highly used area was divided

between the area north of West Pass and the area around Alligator Pass. Despite

differences in patterns of use, areas north of West Pass and adjacent to Alligator Pass,

were highly used by Gulf sturgeon during both seasons (Figures 13 and 14).

Distribution of Benthic Invertebrates and Sediment Types

Sand was the major component of the sediment on a percentage basis at most of the

benthic core sites (n = 28), ranging from 12.8 to 86.4% (58.8%, 16.8). Very Fine Sand

comprised 5.4 to 50.0% (25.2% + 13.5) of the sediment at each core site. Percent Oyster

Shell at core sites ranged from 0.6 to 67.0% (9.9% + 13.6) and percent Small Shell was

usually low, but constant across all sites ranging from 5.3 to 15.0% (6.1% + 3.6). Mean

and first standard deviation for the sediment size types from the five samples collected at

each of the 28 benthic core sites is presented in Table 4.

Abundance and biomass of all invertebrates found in benthic cores collected from

the Suwannee River estuary, excluding polychaetes, are listed in Table 5. In all 28 cores

collected, the relative total abundance of all phyla was comprised of 82.5% arthropods

(crustaceans), 7.9% brachiopods, 2.8% echinoderms (brittle stars and sand dollars), and

6.7% molluscs (bivalves and gastropods) (Table 5, Figure 15). On a relative basis,









arthropods comprised 27.7%, brachiopods 20.2%, echinoderms 32.1%, and molluscs

20.12%, of the total invertebrate biomass collected from cores (Table 5, Figure 16).

Although polychaetes could not be accurately identified, it was determined that members

of seven families were present: Glyceridae, Onuphidae, Opheliadae, Oweniidae,

Pectinaridae, Pilargidae, and Polynoidae.

Significant differences were observed in the relative abundance and absolute

number of genera collected by the core method compared to the petite ponar grab

method. Specifically, there was a significant difference in the relative abundance of the

eight major invertebrate groups collected (amphipods, bivalves, brachiopods, brittle stars,

decapods, gastropods, isopods and sand dollars) in five out of the six comparisons made

between cores and grabs (Fisher's exact tests, n = 8, P <0.01) (Table 6). However, in one

comparison, in which sand was the predominant sediment type, no difference between the

two methods was detected (Fisher's exact test, n = 8, P = 0.38). In addition significantly

more genera were collected by the core method compared to the petite ponar grab method

(Friedman Test, n = 6, S = 6.00, P < 0.02) (Table 6).

Relocations of Gulf Sturgeon in Relation to Environmental Parameters, and Benthic
Invertebrate Distribution

Environmental Parameters

Bottom water temperatures at relocation positions of Gulf sturgeon during the fall

of 2001 ranged from 20.0 to 22.8 C (21.4 0.9 C). In the spring of 2002, bottom

temperatures at relocations ranged from 18.4 to 26.5 C (22.8 2.3 C). Bottom

temperatures at fall 2001 positions were significantly colder than bottom temperatures at

relocations in the spring of 2002 (Paired, two-tail, t-test n = 38, t = -3.14, P = 0.004)

(Figure 17).









Bottom salinities at relocation positions of Gulf sturgeon during the fall of 2001

ranged from 21.6 to 35.1 ppt (29.2 + 3.9 ppt) and bottom salinities during the spring of

2002 ranged from 15.2 to 31.2 ppt (23.3 5.1 ppt). Average bottom salinity at positions

in the fall of 2001 was significantly higher than that of the spring of 2002 (Satterthwaite

Unequal Variance, two-tail, t-test, n = 36, t = 2.69, P = 0.011) (Figure 17).

Dissolved oxygen concentrations near the bottom at relocation positions ranged

from 6.0 to 9.8 mg/L (7.4 + 1.0 mg/L). No significant difference was detected between

average dissolved oxygen near the bottom at positions during the fall of 2001 compared

to those in the spring of 2002 (Satterthwaite Unequal Variance, two-tail, t-test, n = 38, t =

0.15, P = 0.886).

Relocations of Gulf sturgeon during the fall of 2001 were not significantly

correlated with any of the tested environmental variables at the c = 0.1 level (Table 7).

However, relocations during the spring of 2002 were positively correlated with dissolved

oxygen, and negatively correlated with Oyster Shell and Small Shell (Spearman Rank

Correlation test, P < 0.1) (Table 8).

In addition, when sediment type was clustered using the Ward's minimum variance

method, and area within each cluster was compared to the frequency of relocations of

Gulf sturgeon within that cluster, relocations were significantly distributed according to

sediment type (Fisher's exact test, n = 4, P <0.001) (Figures 18 and 19, Table 9). When

compared to the area within each sediment cluster, the frequency of relocations was

comparatively highest in cluster number 2. Sites in cluster 2 were 76.4 to 86.4% Sand,

6.4 to 14.8% Very Fine Sand, and < 8% Small Shell and Oyster Shell (Figure 19, Tables

9 and 10).









Invertebrate Distribution

No correlation was detected between relocations of Gulf sturgeon in the fall of

2001 and relocations in the spring of 2002 (Spearman Rank Correlation test, p = 0.00134,

P = 0.99); however, both fall 2001 and spring 2002 relocations were significantly

correlated with the abundance and biomass of Glottidiapyramidata (Tables 11 and 12).

In addition, relocations in the fall of 2001 were significantly positively correlated with

the abundance and biomass of two brittle star genera: Amphipholis and Ophiactis,

molluscs: Corbula, Crassinella, and Parvilucina, and crabs: Euryplax and Portunus

(Spearman Rank Correlation test, P < 0.1) (Table 11). Relocations in the spring of 2002

were significantly positively correlated with the biomass of the amphipod Ampelisca as

well as the abundance and biomass of the clam Ensis (Spearman Rank Correlation test, P

< 0.1) (Table 12).

Relocations of Gulf sturgeon within the Main Suwannee tracking area (MSTA)

during the fall of 2001 and the spring of 2002 (n = 38) were not significantly distributed

according to total invertebrate biomass (Fisher's exact test, n = 4, P = 0.106) (Table 13,

Figures 20 and 21). However, when compared to the area within each cluster, frequency

of relocations of sturgeon was comparatively highest in cluster number 4, the cluster with

the lowest overall invertebrate biomass (Figure 21, Tables 13 and 14).

Relocations during the fall of 2001 and the spring of 2002 were significantly

distributed according to both the abundance and the biomass of the Gulf sturgeon's main

prey resources (Murie and Parkyn 2002): amphipods (Ampelisca), brachiopods (Glottidia

pyramidata), and brittle stars (Amphiuridae and Ophiactidae) (Abundance: Fisher's exact

test, n = 5, P <0.001, Biomass: Fisher's exact test, n = 4, P<0.002) (Figures 22-25, Tables









15-18). When compared to area within each prey abundance cluster, the frequency of

relocations of Gulf sturgeon was comparatively highest in cluster number 3. Cluster

number 3 had high abundances of all prey resources and the highest numeric abundance

of brachiopods, the dominant prey organism observed in stomach contents. In addition,

the frequency of relocations of sturgeon on a unit area basis was lowest in clusters 2 and

5, which had the lowest average number of brachiopods (Figure 23, Tables 15 and 16).

However, when relocations of Gulf sturgeon were compared on a unit basis to area within

each prey biomass cluster, the frequency of relocations of sturgeon was comparatively

highest in cluster 2 followed by cluster 3, which had low to medium prey biomass (Figure

25, Tables 17 and 18).

Relocations of Gulf sturgeon during the fall of 2001 and the spring of 2002

sampling periods were significantly distributed according to both the abundance and the

biomass of brachiopods (Abundance: Fisher's exact test, n = 4, P < 0.001, Biomass:

Fisher's exact test, n = 4, P = 0.007) (Figures 26-31, Tables 19-22). When compared to

the area within each brachiopod abundance cluster, frequency of relocations of Gulf

sturgeon was comparatively highest in cluster number 4. Cluster number 4 also had the

highest overall abundance of brachiopods. In addition, the frequency of relocations of

sturgeon on a unit area basis was lowest in cluster 2, which had no brachiopods (Figure

27, Tables 19 and 20). Relocations of Gulf sturgeon appear distributed in the Suwannee

River estuary in a pattern similar to the abundance ofbrachiopods (Figure 28). When

compared to the area within each brachiopod biomass cluster, the frequency of

relocations of sturgeon was comparatively the highest in cluster 2, which had

low/medium brachiopod biomass (Figure 30, Tables 21 and 22). Relocations of Gulf









sturgeon did not appear distributed in a similar pattern as that of brachiopod biomass

(Figure 31).

Environmental Parameters and Benthic Invertebrate Distribution

Canonical correspondence analysis (CCA) was used to explore the relationship

between the numerical abundance of invertebrates, the frequency of relocations of Gulf

sturgeon during the fall and the spring, and the tested environmental parameters in the

Suwannee River estuary. The first three axes in the CCA of genera abundances in

relation to the seven tested environmental variables (Very Fine Sand, Sand, Small Shell,

Oyster Shell, Distance from the closest mouth of the Suwannee River (DFRM),

Dissolved Oxygen, and Depth), explained 33.0% of the variation in the invertebrate data

matrix (Table 23). The first canonical axis, which explained 15.4% of the variation, was

highly positively correlated (>0.399) with DFRM and Depth and negatively correlated

with Very Fine Sand. The second canonical axis, which explained 11.0% of the

variation, was highly positively correlated (>0.399) with Very Fine Sand, and negatively

correlated with Small Shell and Oyster Shell. The third canonical axis, which explained

6.7% of the variation, was positively correlated (>0.399) with Depth and Very Fine Sand

and negatively correlated with Sand (Tables 23 and 24). Dissolved Oxygen was not as

highly correlated with any axis as the other environmental parameters were and therefore

did not explain as of much variation in the invertebrate community (Table 24).

Many genera appear to have been ordinated in response to an environmental

gradient in the Suwannee River estuary. Habitats varied from inshore, shallow habitats

characterized by Very Fine Sand, inhabited by genera such as the amphipod Ampelisca,

the brittle star Amphiodia, and the crab Pinnixa, to deeper, more offshore habitats,

inhabited by genera such as molluscs: Pyramidella, Marginella, Solemya, and Olivella.









There are a number of genera; however, such as the crab Eurypanopeus, and the

gastropods Cantharus and Nassarius, which appear to be more associated with Oyster

Shell, than they are with the above described gradient (Table 25, Figure 32). When

collected in the field, these genera were mostly associated with living Oyster bar in the

Suwannee River estuary.

The frequency of relocations of Gulf sturgeon in the fall of 2001 and those in the

spring of 2002 had relatively high scores on the first, followed by the third canonical

axes, associating relocations more with the combinations of environmental parameters

described by those axes. However, relocations of sturgeon in the fall of 2001 had a

positive score on the first axis, whereas that score for the spring of 2002 was negative,

illustrating a difference in habitat use during these two seasons (Table 25). Canonical

correspondence analysis scores for relocations in the fall of 2001 associated sturgeon,

during this season, with more offshore areas over sediments with a low percentage of

Very Fine Sand, but comprised more highly of Sand/Small Shell. In contrast, relocations

in the spring of 2002 were more associated with inshore, shallow areas, over mixed

sediments (Tables 24 and 25). Neither fall 2001, nor spring 2002 relocation scores were

exactly coincident with any of their major prey resources in the Suwannee River estuary;

amphipods, brachiopods, and brittle stars (Amphiodia, Amphipholis, Ophiophragmus, and

Ophiactis); however, spring 2002 relocation scores on each axis more closely resembled

those of some of their prey resources than did relocations in the fall, 2001 (Figures 32

and 33). Glottidia, the sturgeon's main prey resource in the Suwannee River estuary

(Murie and Parkyn 2002), had a high negative score for canonical axis three, illustrating









that this genera was more associated with shallow, sandy habitats with low Very Fine

Sand content (Table 25, Figures 32 and 33).

Invertebrates were also grouped at the family level to allow for comparison of the

effects of taxonomic level on how invertebrate abundance is ordinated in relation to

environmental parameters. The first three axes in the CCA of the abundance of

invertebrates at the family level in relation to the seven tested environmental variables:

Very Fine Sand, Sand, Small Shell, Oyster Shell, DFRM, Dissolved Oxygen, and Depth,

explained 38.2.0% of the variation in the data (Table 26). The first canonical axis, which

explained 19.1% of the variation, was highly negatively correlated with Small Shell and

Oyster Shell. The second canonical axis, which explained 12.2% of the variation, was

highly positively correlated with Small Shell, Depth, and DFRM and negatively

correlated with Very Fine Sand. The third canonical axis, which explained 6.9% of the

variation, was positively correlated with Sand and negatively correlated with Very Fine

Sand and Depth (Tables 26 and 27). As seen in the CCA at the genera level, Dissolved

Oxygen was not as highly correlated to any of the canonical axes as the other

environmental variables, indicating that Dissolved Oxygen contributed less to the

structuring of the community than did other environmental parameters (Table 27).

Overall, the canonical correspondence analysis at the family level did not appear to

differ greatly from analysis at the genera level (Figures 32 and 34). The three basic

habitat types: 1) high percentage Very Fine Sand and close to a mouth of the Suwannee

River; 2) high percentage Oyster Shell; 3) and deep and away from a mouth of the

Suwannee River, were still observed, but there was a greater emphasis on Oyster Shell

habitat when analysis was conducted at the family level (Figure 34).






35


Canonical correspondence analysis of relocations of Gulf sturgeon in the fall of

2001 and in the spring of 2002 at the family level had the highest scores on the second

followed by the third canonical axes (Table 28). As seen in the analysis conducted at the

genera level, fall 2001 relocations were more associated with areas farther offshore over

sediments with higher Sand and Small Shell composition and lower Very Fine Sand

composition, while spring 2002 relocations were associated with shallower, more inshore

habitats (Tables 27 and 28).










Table 3. Duration of residency in the Suwannee River estuary by each ultrasonic-
tagged Gulf sturgeon during the study period from November 2001 through
May 2002. Interval was calculated as the time in days between the Start Date
and the End Date; Start Date refers to the date when the fish was first
relocated in the estuary; End Date refers to the date when the fish was last
relocated in the estuary; R = the number of days that an individual fish was
relocated; M = Male; F = Female; and NR = Not Relocated.
Fish Sex Fall 2001 Spring 2002
Identifier Start End Interval R Start End Interval R
Date Date (Days) Date Date (Days)


A M 12/15 12/15
B M NR
C M 12/15 12/19
D M 11/11 11/11
E M 11/20 11/20
F M 12/10 12/15
G M 12/2 12/2
H M 11/7 11/7


1 NR


2 3/18 4/17
1 NR
1 NR
2 3/17 3/17
1 4/10 4/17


1 3/24


I M NR
J M NR
K M NR
L M NR


M F 11/18 11/18


1 3/29 4/10


N F NR
O F NR
P F NR
Q F NR


3/28 3/28


3/16 3/18


R F NR NR










Table 4. Mean and first standard deviation of each sediment size type collected from
28 benthic core location sites in the Suwannee River estuary, Florida. Five
cores were collected from each core site from April 22 through May 9, 2002.
At each core site, sediment was collected from a central location and then
collected from four satellite locations (all 30.5 m from the central location) by
swimming bearings of 50, 140, 230 and 320 degrees from the central location.
Site Very Fine Sand Sand Small Shell Oyster Shell
(X'+ lsd) (X + Isd) (X + Isd) (X0 + sd)
2X 15.4 4.6 53.6 9.2 6.6 1.5 24.4 11.8
2Y 10.8 5.5 68.6 13.0 11.2 5.0 9.4 6.3
2Z 10.0 + 0 80.0 3.5 5.5 + 2.7 4.5 1.1
3X 27.0 11.0 65.6 10.9 2.9 1.2 4.5 3.3
3Y 11.0 5.5 76.4 6.1 7.6 + 2.5 5.0 2.1
3Z 27.0 + 8.4 58.2 7.8 8.0 2.1 6.8 3.4
4X 25.4 8.6 66.4 7.1 4.4 1.3 3.8 1.1
4Y 14.0 3.8 76.4 5.8 5.4 1.8 4.2 1.6
4Z 17.0 7.0 64.2 6.9 8.8 + 1.6 10.0 + 5.9
5X 35.0 15.4 47.0 14.6 4.0 + 1.4 14.0 + 5.7
5Y 20.0 7.1 72.2 6.5 3.3 + 1.6 4.5 + 2.4
5Z 17.6 5.6 51.4 15.3 13.2 + 2.0 17.8 + 11.1
6X 46.0 4.2 43.2 5.4 5.2 + 0.4 5.6 + 1.3
6Y 5.4 4.6 12.8 6.6 14.2 + 6.9 67.6 + 17.0
6Z 20.1 8.4 63.6 12.2 6.8 + 1.6 9.5 + 5.7
7X 38.6 12.4 50.0 14.3 5.0 + 0.0 6.4 + 2.2
7Y 38.0 + 9.7 49.2 10.3 5.9 + 2.6 6.9 + 3.1
7Z 23.8 9.9 24.6 0.9 15.0 + 3.1 36.6 + 7.3
8X 35.0 15.8 63.6 15.6 0.8 + 0.3 0.6 + 0.4
8Y 35.0 11.2 58.6 11.0 3.2 1.8 3.2 1.8
8Z 6.4 2.7 80.0 14.2 6.2 5.0 7.4 11.1
9X 46.0 + 9.6 46.2 13.1 4.2 1.8 3.6 2.2
9Y 37.0 2.7 57.1 4.3 3.2 1.8 2.7 1.4
9Z 26.0 13.4 60.0 10.6 8.0 2.7 6.0 2.2
S1 7.2 5.1 86.4 6.1 2.7 1.3 3.7 3.5
S2 14.8 3.2 80.1 3.6 2.3 0.3 2.8 1.3
S3 50.0 15.0 43.6 13.0 3.2 1.0 3.2 1.0
S4 46.0 2.6 47.2 2.2 4.2 1.1 2.6 1.3











Table 5. Density in abundance and biomass of all invertebrates, excluding polychaetes,
collected from benthic core sites in the Suwannee River estuary, Florida. Ten
cores, (surface area =81 cm2; volume = 1234 cm3) were collected from 28
cores from April 22 through May 9, 2002. All organisms retained by a 0.85
mm sieve or coarser were collected.
Phylum Family Genus Species Abundance/ Biomass
m2 (g) / m2
Arthropoda Alpheidae Alpheus armillatus 0.3304 0.0459
Alpheus sp. 0.1101 0.0008
Ampeliscidae Ampelisca verrilli 40.6388 0.3108
vadorum 37.8855 0.1504
Anthuridae Apanthura imaignilca 2.9736 0.0178
Cyathura polita 1.9824 0.0211
Balanidae Balanus cf eberneus 313.7665 1.5135
Callianassidae Callianassa sp. 0.2203 0.0032
Goneplacidae cf Euryplax nitida 0.2203 0.0078
Hippolytidae Latreutes parvulus 0.1101 0.0008
Nannasticidae Oxyurostylis smith 0.5507 0.0020
Paguridae Pagurus longicarpus 0.7709 0.0451
Penaeidae Parapenaeus politus 0.1101 0.0015
Pinnotheridae Pinnixa sp. 0.6608 0.0128
Porcellanidae Euceramus praelongus 0.3304 0.0081
Petrolisthes armatus 0.2203 0.1028
Portunidae Pontunus floridanus 0.1101 0.0416
Xanthidae Eurypanopeus depressus 3.6344 1.0021
Brachiopoda Lingulidae Glottidia pyramidata 38.8767 2.3800
Chordata Branchiostomidae Branchiostoma sp. 0.1101 0.0010
Echinodermata Amphiuridae Amphiodia atra 1.7621 0.4291
Amphipholis gracillima 5.6167 0.7977
Ophiophragmus filograneus 2.6432 0.4897
wurdemani 0.5507 0.2132
Mellitidae Mellita tenuis 0.5507 1.7060
Ophiactidae Ophiactis sp. 2.6431 0.1915
Mollusca Arcidae Anadara transversa 0.1101 <0.0001
Buccinidae Cantharus cancellarius 0.6608 0.0963
Corbulidae Corbula contract 0.3304 0.0038
Crassatellidae Crassinella lunulata 0.1101 0.0006
Crepidulidae Crepidula plana 3.0837 0.0485
Lucinidae Parvilucina multilineata 0.1101 0.0011
Mactridae Mactra fragilis 0.1101 0.0175
Marginellidae Mlarginella apicina 4.5154 0.1425
Melongenidae Melongena corona 0.1101 1.2343
Muricidae Calotrophon ostrearum 0.1101 0.0025
Mytilidae Amygdalum papyrium 0.3304 0.0156
Brachidontes exustus 6.3877 0.1238
Ischadium recurvum 2.4230 0.0822
Nassariidae Nassarius vibex 0.6608 0.0342
Naticidae Natica pusilla 0.3304 0.0058
Nuculanidae Nuculana acuta 0.2203 0.0170
Olividae Olivella floralia 2.3128 0.1622
Pyramidellidae Boonea impressa 2.423 0.0072
Pyramidella crenulata 0.5507 0.0050
Solemyidae Solemya occidentalis 1.1013 0.1655
Solenidae Ensis minor 0.8811 0.0369
Tellinidae Tellina cf texana 5.1762 0.1189
Tellina cf versicolor 1.6520 0.1179
Terebridae Terebra dislocata 0.1101 0.1874
Ungulinidae Diplodonta semiaspera 1.3216 0.0750










Table 6. Comparisons between the core and petite ponar grab methods for the
collection of invertebrates in the Suwannee River estuary, Florida, in terms of
total number of genera collected and relative abundance of invertebrate
groups. Fisher's exact tests were used to determine differences in relative
abundance of the eight invertebrate groups (amphipods, brachiopods,
bivalves, brittle stars, decapods, gastropods, isopods, and sand dollars) found
at these six sites. Cores were collected from April 22 through May 9, 2002.
Grabs were collected from February 24 through March 30, 2002.
Site Predominant Number of Genera Number of Genera Fisher's Exact
Sediment Type Collected by Core Method Collected by Grab Method P value
3X Very Fine Sand 6 3 P < 0.001

5Y Sand 11 6 P = 0.383

7Y Very Fine Sand 9 2 P = 0.004

7Z Small Shell and 13 2 P < 0.001
Oyster Shell
8Y Very Fine Sand 8 6 P < 0.001
and Sand
9Z Very Fine Sand 8 4 P < 0.001
and Sand







40


Table 7. Spearman Rank Correlations (p) between relocation positions of Gulf
sturgeon in the fall of 2001 and environmental parameters collected from the
Suwannee River estuary, Florida, from April 22 through May 9, 2002. No
correlations were significant at the P < 0.1 level. DFRM = distance from the
closest mouth of the Suwannee River.
Environmental Parameter p P
Very Fine Sand -0.205 0.294
Sand 0.188 0.338
Small Shell 0.018 0.927
Oyster Shell -0.108 0.583
Dissolved Oxygen -0.082 0.680
DFRM 0.048 0.807
Depth 0.012 0.953







41


Table 8. Spearman Rank Correlations (p) between relocation positions of Gulf
sturgeon in the spring of 2002 and environmental parameters collected from
the Suwannee River estuary, Florida, from April 22 through May 9, 2002.
Correlations with P < 0.1 are indicated with a and considered significant.
DFRM = distance from the closest mouth of the Suwannee River.
Environmental Parameter p P
Very Fine Sand -0.048 0.810
Sand 0.173 0.380
Small Shell -0.384 0.044*
Oyster Shell -0.321 0.096*
Dissolved Oxygen 0.343 0.074*
DFRM -0.237 0.225
Depth -0.274 0.158











Table 9. Cluster number and percentage of each sediment size type at each of the 28
benthic core sites collected in the Suwannee River estuary, Florida, from April
22 through May 9, 2002. Clustering was completed using the Ward's
minimum variance method (PC-ORD 4).
Site Cluster Number Very Fine Sand Sand Small Shell Oyster Shell
2X 1 15.4 53.6 6.6 24.4
2Y 1 10.8 68.6 11.2 9.4
3X 1 27.0 65.6 2.9 4.5
3Z 1 27.0 58.2 8.0 6.8
4X 1 25.4 66.4 4.4 3.8
4Z 1 17.0 64.2 8.8 10.0
5Y 1 20.0 72.2 3.3 4.5
5Z 1 17.6 51.4 13.2 17.8
6Z 1 20.1 63.6 6.8 9.5
9Z 1 26.0 60.0 8.0 6.0

2Z 2 10.0 80.0 5.5 4.5
3Y 2 11.0 76.4 7.6 5.0
4Y 2 14.0 76.4 5.4 4.2
8Z 2 6.4 80.0 6.2 7.4
S1 2 7.2 86.4 2.7 3.7
S2 2 14.8 80.1 2.3 2.8

5X 3 35.0 47.0 4.0 14.0
6X 3 46.0 43.2 5.2 5.6
7X 3 38.6 50.0 5.0 6.4
7Y 3 38.0 49.2 5.9 6.9
8X 3 35.0 63.6 0.8 0.6
8Y 3 35.0 58.6 3.2 3.2
9X 3 46.0 46.2 4.2 3.6
9Y 3 37.0 57.1 3.2 2.7
S3 3 50.0 43.6 3.2 3.2
S4 3 46.0 47.2 4.2 2.6

6Y 4 5.4 12.8 14.2 67.6
7Z 4 23.8 24.6 15.0 36.6







43


Table 10. Area within each sediment cluster compared to the frequency of relocations of
Gulf sturgeon within that cluster. Sediment was collected in the Suwannee
River estuary, Florida, from April 22 through May 9, 2002. Clustering was
completed using the Ward's minimum variance method (PC-ORD 4).
Polygons representing each core site were created by interpolation between
core location points using a Thiessen polygon interpolation method. Core
sites with the same cluster number were then grouped and area within each
cluster was calculated (ArcView 3.2).
Cluster Number Cluster Area Frequency of Sturgeon Frequency of Sturgeon
(km2) Relocations Relocations/Cluster Area
1 60.7 6 0.10
2 28.0 20 0.71
3 45.7 10 0.22
4 9.3 2 0.22











Table 11. Spearman Rank Correlations (p) between relocation positions of Gulf
sturgeon in the fall of 2001 and the abundance and biomass of all invertebrate
genera (excluding polychaetes) collected in the Suwannee River estuary,
Florida, from April 22 through May 9, 2002. Correlations with a P < 0.1 are
indicated with a and considered significant.
Phylum Genus Abundance (p) Abundance (P) Biomass (p) Biomass (P)
Arthropoda Alpheus 0.218 0.266 0.194 0.323
Ampelisca -0.122 0.537 -0.077 0.698
Apanthura 0.108 0.585 0.101 0.611
Balanus -0.089 0.651 -0.089 0.651
Callianassa -0.129 0.514 -0.129 0.514
Cyathura -0.215 0.272 -0.215 0.272
Euceramus -0.161 0.414 -0.160 0.415
Eurypanopeus 0.108 0.585 0.118 0.551
cf Euryplax 0.540 0.003* 0.536 0.004*
Latreutes -0.089 0.651 -0.089 0.651
Oxyurostylis 0.074 0.708 0.083 0.675
Pagurus -0.040 0.841 -0.025 0.901
Parapenaeus -0.089 0.651 -0.089 0.651
Petrolisthes -0.089 0.651 -0.089 0.651
Pinnixa -0.216 0.270 -0.215 0.272
Portunus 0.375 0.049* 0.375 0.049*

Brachiopoda Glottidia 0.361 0.059* 0.373 0.051*

Chordata Branchiostoma -0.089 0.651 -0.089 0.651

Echinodermata Amphiodia -0.115 0.562 -0.090 0.649
Amphipholis 0.448 0.017* 0.500 0.007*
Mellita 0.098 0.620 0.098 0.620
Ophiactis 0.431 0.022* 0.400 0.035*
Ophiophragmus -0.081 0.684 -0.080 0.686

Mollusca Amygdalum -0.129 0.514 -0.129 0.514
Anadara -0.089 0.651 -0.089 0.651
Brachidontes -0.089 0.651 -0.089 0.651
Boonea -0.089 0.651 -0.089 0.651
Calotrophon -0.089 0.651 -0.089 0.651
Cantharus -0.189 0.336 -0.189 0.336
Corbula 0.375 0.049* 0.375 0.049*
Crassinella 0.375 0.049* 0.375 0.049*
Crepidula -0.129 0.514 -0.129 0.514
Ensis 0.138 0.485 0.183 0.350
Ischadium -0.129 0.514 -0.129 0.514
Mactra -0.089 0.651 -0.089 0.651
Marginella 0.188 0.338 0.128 0.516
Melongena -0.089 0.651 -0.089 0.651
Nassarius -0.242 0.214 -0.240 0.219
Natica -0.129 0.514 -0.129 0.514
Nuculana -0.129 0.514 -0.129 0.514
Olivella -0.241 0.217 -0.240 0.219
Parvilucina 0.375 0.049* 0.375 0.049*
Pyramidella 0.128 0.518 0.138 0.485
Solemya -0.160 0.415 -0.160 0.415
Tellina -0.241 0.216 -0.257 0.188
Terebra -0.089 0.651 -0.089 0.651











Table 12. Spearman Rank Correlations (p) between relocation positions of Gulf
sturgeon in the spring of 2002 and the abundance and biomass of all
invertebrate genera (excluding polychaetes) collected in the Suwannee River
estuary, Florida, from April 22 through May 9, 2002. Correlations with a P <
0.1 are indicated with a and considered significant.
Phylum Genus Abundance (p) Abundance (P) Biomass (p) Biomass (P)
Arthropoda Alpheus -0.054 0.783 -0.039 0.844
Ampelisca 0.243 0.213 0.344 0.073*
Apanthura 0.301 0.120 0.261 0.179
Balanus 0.117 0.554 0.117 0.554
Callianassa -0.262 0.178 -0.262 0.179
Cyathura 0.060 0.761 0.047 0.811
Euceramus -0.062 0.753 -0.062 0.753
Eurypenopeus 0.037 0.850 0.031 0.875
cf Euryplax -0.262 0.178 -0.258 0.194
Latreutes -0.182 0.355 -0.182 0.355
Oxyurostylis -0.168 0.394 -0.143 0.469
Pagurus 0.116 0.557 0.065 0.744
Parapenaus 0.117 0.554 0.117 0.554
Petrolithes 0.117 0.554 0.117 0.554
Pinnixia 0.184 0.349 0.186 0.344
Portunas -0.182 0.355 -0.182 0.355

Brachiopoda Glottidia 0.514 0.005* 0.410 0.030*

Chordata Branchiostoma -0.182 0.355 -0.182 0.355

Echinodermata Amphiodia 0.200 0.307 0.195 0.320
Amphipholis 0.042 0.834 0.021 0.917
Mellita -0.327 0.090* -0.326 0.090*
Ophiactis -0.217 0.268 -0.211 0.280
Ophiofragmous -0.036 0.854 -0.054 0.786

Mollusca Amydalum 0.168 0.392 0.168 0.392
Anadara -0.182 0.355 -0.182 0.355
Brachiodontes -0.182 0.355 -0.182 0.355
Boonea -0.182 0.355 -0.182 0.355
Calotrophon -0.182 0.355 -0.182 0.355
Cantharus 0.285 0.142 0.276 0.155
Corbula -0.182 0.355 -0.182 0.355
Crassinella -0.182 0.355 -0.182 0.355
Crepidula 0.168 0.392 0.168 0.392
Ensis 0.449 0.017* 0.461 0.014*
Ishadium 0.168 0.392 0.168 0.392
Mactra -0.182 0.355 -0.182 0.355
Marginella -0.361 0.059* -0.287 0.139
Melongena -0.182 0.355 -0.182 0.355
Nassarius 0.112 0.572 0.075 0.705
Natica 0.168 0.392 0.168 0.392
Nuculana 0.168 0.392 0.168 0.392
Olivella -0.365 0.056* -0.360 0.060*
Parvilucina -0.182 0.355 -0.182 0.355
Pyramidella -0.327 0.090* -0.326 0.090*
Solemya -0.326 0.090* -0.326 0.090*
Tellina -0.226 0.248 -0.450 0.016*
Terebra -0.182 0.355 -0.182 0.355











Table 13. Cluster number and total invertebrate biomass (excluding polychaetes) at each
benthic core site collected from the Suwannee River estuary, Florida, from
April 22 through May 9, 2002. Clustering was completed using the Ward's
minimum variance method (PC-ORD 4).
Site Cluster Number Invertebrate Biomass
2X 1 12.0985
3X 1 9.0836
4X 1 7.1875
8Z 1 13.4400

6Y 2 24.8926

2Y 3 2.7734
3Y 3 3.7442
5Y 3 3.6717
8Y 3 4.0191
9X 3 2.4818
9Y 3 3.6903
S3 3 3.1500

2Z 4 0.6318
3Z 4 1.6278
4Y 4 1.6589
4Z 4 0.7329
5X 4 0.3383
5Z 4 0.8054
6X 4 0.4825
6Z 4 1.2888
7X 4 0.2980
7Y 4 1.7902
7Z 4 1.8007
8X 4 0.2473
9Z 4 1.3653
S1 4 1.5019
S2 4 1.1823
S4 4 0.0475







47


Table 14. Area within each total invertebrate biomass cluster compared to the frequency
of relocations of Gulf sturgeon within that cluster. Invertebrates were
collected in the Suwannee River estuary, Florida, from April 22 through May
9, 2002. Clustering was completed using the Ward's minimum variance
method (PC-ORD 4). Polygons representing each core site were created by
interpolation between core location points using a Thiessen polygon
interpolation method. Core sites with the same cluster number were then
grouped and area within each cluster was calculated (ArcView 3.2).
Cluster Number Cluster Area Frequency of Sturgeon Frequency of Sturgeon
(km2) Relocations Relocations/Cluster Area
1 26.7 3 0.11
2 3.6 1 0.28
3 35.1 6 0.17
4 78.2 28 0.36











Table 15. Cluster number and numerical abundance of major prey resources: amphipods
(Ampelisca), brachiopods (Glottidiapyramidata), and brittle stars
(Amphiuridae and Ophiactidae), at each of the 28 benthic core sites collected
in the Suwannee River estuary, Florida, from April 22 through May 9, 2002.
Clustering was completed using the Ward's minimum variance method (PC-
ORD 4). Prey abundances were logio(x +1) transformed to reduce variation
between the invertebrate families.
Site Cluster Number Amphipods Brachiopods Brittle stars
2X 1 32 1 3
9X 1 25 0 8
9Y 1 16 1 23
S3 1 6 0 18

5X 2 11 0 0
6X 2 71 0 0
7X 2 278 0 0
S4 2 39 0 0

3X 3 50 34 5
4X 3 34 51 1
5Y 3 13 9 3
7Y 3 151 11 4
8Y 3 54 14 15
S1 3 24 68 1
S2 3 52 124 0

2Y 4 1 13 2
3Y 4 0 19 0
4Y 4 0 3 5
6Z 4 0 2 3
7Z 4 0 2 3

2Z 5 0 0 0
3Z 5 0 0 0
4Z 5 2 1 2
5Z 5 0 0 0
6Y 5 1 0 1
8X 5 0 0 0
8Z 5 0 0 0
9Z 5 7 0 7







49


Table 16. Area within each prey abundance cluster compared to the frequency of
relocations of Gulf sturgeon within that cluster. Prey invertebrates were
collected in the Suwannee River estuary, Florida, from April 22 through May
9, 2002. Clustering was completed using the Ward's minimum variance
method (PC-ORD 4). Polygons representing each core site were created by
interpolation between core location points using a Thiessen polygon
interpolation method. Core sites with the same cluster number were then
grouped and area within each cluster was calculated (ArcView 3.2).
Cluster Number Cluster Area Frequency of Sturgeon Frequency of Sturgeon
(km2) Relocations Relocations/Cluster Area
1 21.7 4 0.18
2 20.1 1 0.05
3 33.1 21 0.63
4 28.1 10 0.36
5 40.6 2 0.05











Table 17. Cluster number and total biomass of main prey resources: amphipods
(Ampelisca), brachiopods (Glottidiapyramidata), and brittle stars
(Amphiuridae and Ophiactidae), at each of the 28 benthic core sites collected
from the Suwannee River estuary, Florida, from April 22 through May 9,
2002. Clustering was completed using the Ward's minimum variance method
(PC-ORD 4).
Site Cluster Number Prey Biomass
2X 1 0.5648
2Z 1 0.3185
4Z 1 0.3053
5Y 1 0.5236
5Z 1 0
6X 1 0.0927
6Y 1 0.0048
6Z 1 0.3924
7X 1 0.2703
7Z 1 0.4996
8X 1 0.0529
8Z 1 0
S4 1 0.0372

2Y 2 2.4412
3Z 2 1.3100
4Y 2 1.0730
5X 2 0.9240
7Y 2 1.4642
9X 2 2.1195
9Z 2 0.9600
S1 2 1.3123
S2 2 1.4771

3Y 3 3.4610
8Y 3 4.0232
9Y 3 2.9378
S3 3 3.0438

3X 4 7.6981
4X 4 7.4140







51


Table 18. Area within each prey biomass cluster compared to the frequency of
relocations of Gulf sturgeon within that cluster. Prey invertebrates were
collected in the Suwannee River estuary, Florida, from April 22 through May
9, 2002. Clustering was completed using the Ward's minimum variance
method (PC-ORD 4). Polygons representing each core site were created by
interpolation between core location points using a Thiessen polygon
interpolation method. Core sites with the same cluster number were then
grouped and area within each cluster was calculated (ArcView 3.2).
Cluster Number Cluster Area Frequency of Sturgeon Frequency of Sturgeon
(km2) Relocations Relocations/Cluster Area
1 69.1 7 0.10
2 45.6 24 0.53
3 16.3 5 0.31
4 12.6 2 0.16







52


Table 19. Cluster number and abundance of brachiopods, Glottidiapyramidata, at each
of the 28 benthic core sites collected in the Suwannee River estuary, Florida,
from April 22 through May 9, 2002. Clustering was completed using the
Ward's minimum variance method (PC-ORD 4) and brachiopod abundances
were logio(x +1) transformed to reduce the influence of very high abundances.
Site Cluster Number Brachiopod Abundance
2X 1 1
4Y 1 3
4Z 1 1
6Z 1 2
7Z 1 2
9Y 1 1


2Y 3 13
3Y 3 19
5Y 3 9
7Y 3 11
8Y 3 14

3X 4 34
4X 4 51
S1 4 68
S2 4 124







53


Table 20. Area within each brachiopod abundance cluster compared to the frequency of
relocations of Gulf sturgeon within that cluster. Brachiopods were collected
in the Suwannee River estuary, Florida, from April 22 through May 9, 2002.
Clustering was completed using the Ward's minimum variance method (PC-
ORD 4). Polygons representing each core site were created by interpolation
between core location points using a Thiessen polygon interpolation method.
Core sites with the same cluster number were then grouped and area within
each cluster was calculated (ArcView 3.2).
Cluster Number Cluster Area Frequency of Sturgeon Frequency of Sturgeon
(km2) Relocations Relocations/Cluster Area
1 36.7 10 0.27
2 62.7 5 0.08
3 25.5 7 0.27
4 18.7 16 0.86











Table 21. Cluster number and biomass of brachiopods, Glottidiapyramidata, at each of
the 28 benthic core sites collected in the Suwannee River estuary, Florida,
from April 22 through May 9, 2002. Clustering was completed using the
Ward's minimum variance method (PC-ORD 4).
Site Cluster Number Brachiopod Biomass
2X 1 0.0016
2Z 1 0
3Z 1 0
4Z 1 0.0001
5X 1 0
5Z 1 0
6X 1 0
6Y 1 0
6Z 1 0.0430
7X 1 0
7Y 1 0.1107
7Z 1 0.1311
8X 1 0
8Z 1 0
9X 1 0
9Y 1 0.0242
9Z 1 0
S3 1 0
S4 1 0

4Y 2 0.6379
5Y 2 0.4381
8Y 2 0.9972
S1 2 0.9335
S2 2 1.0706

2Y 3 2.1814
3Y 3 3.4610

3X 4 5.6801
4X 4 7.1843







55


Table 22. Area within each brachiopod biomass cluster compared to the frequency of
relocations of Gulf sturgeon within that cluster. Brachiopods were collected
in the Suwannee River estuary, Florida, from April 22 through May 9, 2002.
Clustering was completed using the Ward's minimum variance method (PC-
ORD 4). Polygons representing each core site were created by interpolation
between core location points using a Thiessen polygon interpolation method.
Core sites with the same cluster number were then grouped and area within
each cluster was calculated (ArcView 3.2).
Cluster Number Cluster Area Frequency of Sturgeon Frequency of Sturgeon
(km2) Relocations Relocations/Cluster Area
1 97.6 14 0.14
2 22.3 20 0.90
3 11.1 2 0.18
4 12.6 2 0.16










Table 23. Results of canonical correspondence analysis (CCA) for benthic invertebrate
genera collected from 28 core sites in the Suwannee River estuary, Florida,
from April 22 through May 9, 2002. Invertebrates not collected from at least
3 sites were removed to reduce the effects of rare taxa. Genera were
logio(y+l) transformed; proportional data was arcsin(x/100) transformed; all
other environmental parameters were logio(x+l) transformed. Species -
environmental correlations were conducted using Pearson tests.
Statistic CCA-Axis 1 CCA-Axis 2 CCA-Axis 3

Eigenvalue 0.473 0.337 0.206

Species-Environmental 0.969 0.951 0.899
Correlations

% Variance in species 15.4 11.0 6.7
data explained by the Axis

Cumulative % of variance 15.4 26.3 33.0
in species explained










Table 24. Intraset correlations between the environmental variables examined and the
first three axes in the canonical correspondence analysis (CCA) using
invertebrate genera collected from 28 core sites in the Suwannee River
estuary, Florida, from April 22 through May 9, 2002. Intraset correlations
may help indicate which environmental variables structure the community; the
higher the value, the more the parameter explains variation in the invertebrate
data. Proportional data was arcsin(x/100) transformed; all other
environmental parameters were loglo(x+1) transformed; DFRM = Distance
from the closest mouth of the Suwannee River. Correlations above 0.399 and
below -0.399 were considered more highly correlated than those between
-0.399 and 0.399 and followed by a for emphasis.
Variable CCA-Axis 1 CCA-Axis 2 CCA-Axis 3

Very Fine Sand -0.458* 0.498* 0.544*

Sand 0.359 0.041 -0.531*

Small Shell 0.382 -0.802* -0.023

Oyster Shell -0.337 -0.846* -0.111

Dissolved Oxygen -0.156 -0.037 -0.278

DFRM 0.616* -0.192 0.092


0.579* -0.361


Depth


0.575*










Table 25. Final scores by genera from the canonical correspondence analysis (CCA). A
higher score indicates that the invertebrate's distribution was more highly
correlated to the environmental variables described by the axis. The canonical
correspondence analysis was conducted on genera and environmental
variables collected in the Suwannee River estuary, Florida, from April 22
through May 9, 2002. Invertebrates were logio(y+l) transformed.
Genera CCA-Axis 1 CCA-Axis 2 CCA-Axis 3

Ampelisca -0.451 0.414 -0.021
Amphiodia -0.322 0.281 0.231
Amphipholis -0.093 0.067 0.538
Apanthura 0.012 0.191 -0.199
Cantharus -0.713 -1.044 0.352
Cyathura -1.241 -0.453 0.521
Diplodonta 0.215 -0.204 0.397
Ensis -0.307 0.211 -0.794
Euceramus 0.493 0.139 -0.318
Eurypanopeus -2.263 -3.306 -0.395
Glottidia -0.013 0.273 -0.665
Marginella 1.160 -0.501 -0.223
Mellita 0.608 -0.041 -0.712
Nassarius -0.859 -0.464 -0.175
Olivella 1.331 -0.362 0.192
Ophiophragmus -0.197 0.284 0.590
Ophiactis 0.427 -0.301 0.831
Oxyurostylis -0.050 0.408 -0.178
Pagurus 0.025 0.041 -0.595
Pinnixa -0.729 0.548 1.046
Pyramidella 1.599 -1.056 0.614
Solemya 0.982 -0.477 1.292
Tellina 0.025 0.212 0.414
Sturgeon-Fall 2001 relocations 0.404 -0.041 -0.234
Sturgeon-Spring 2002 relocations -0.452 0.141 -0.304










Table 26. Results of canonical correspondence analysis (CCA) for benthic invertebrate
families collected from 28 core sites in the Suwannee River estuary, Florida,
from April 22 through May 9, 2002. Families not collected from at least 3
sites were removed to reduce the effects of rare taxa. Invertebrates were
logio(y+l) transformed; proportional data was arcsin(x/100) transformed; all
other environmental parameters were loglo(x+l) transformed;. Species -
environmental correlations were conducted using Pearson tests.
Statistic CCA-Axis 1 CCA-Axis 2 CCA-Axis 3

Eigenvalue 0.498 0.319 0.179

Species-Environmental 0.977 0.890 0.881
Correlations

% Variance in species 19.1 12.2 6.9
data explained by the Axis

Cumulative % of variance 19.1 31.3 38.2
in species explained










Table 27. Intraset correlations between the environmental variables examined and the
first three axes in the canonical correspondence analysis (CCA) using
invertebrate families collected from 28 core sites in the Suwannee River
estuary, Florida, from April 22 through May 9, 2002. Intraset correlations
may help indicate which environmental variables structure the community; the
higher the value, the more the parameter explains variation in the invertebrate
data. Proportional data was arcsin(x/100) transformed; all other
environmental parameters were loglo(x+1) transformed; DFRM = Distance
from the closest mouth of the Suwannee River. Correlations above 0.399 and
below -0.399 were considered more highly correlated than those between
-0.399 and 0.399 and followed by a for emphasis.
Variable CCA-Axis 1 CCA-Axis 2 CCA-Axis 3

Very Fine Sand 0.368 -0.482* -0.704*

Sand 0.177 0.252 0.612*

Small Shell -0.687* 0.430* 0.099

Oyster Shell -0.943* 0.009 0.141

Dissolved Oxygen -0.125 -0.298 0.105

DFRM 0.311 0.565* -0.013


-0.002 0.766*


Depth


-0.454*










Table 28. Final scores by family from the canonical correspondence analysis (CCA). A
higher score indicates that the invertebrate's distribution was more highly
correlated to the environmental variables described by the axis. The canonical
correspondence analysis was conducted on family and environmental
variables collected in the Suwannee River estuary, Florida, from April 22
through May 9, 2002. Invertebrates were logio(y+l) transformed.
Family CCA-Axis 1 CCA-Axis 2 CCA-Axis 3

Ampeliscidae 0.266 -0.514 -0.116
Amphiuridae 0.246 -0.059 -0.446
Anthuridae 0.004 -0.203 -0.031
Buccinidae -1.669 -0.118 -0.228
Lingulidae 0.337 -0.173 0.655
Marginellidae 0.153 0.955 -0.114
Mellitidae 0.343 0.640 1.167
Mytilidae -2.770 -0.343 -0.059
Nannasticidae 0.366 -0.295 0.205
Nassaridae -0.305 -0.534 0.037
Olividae 0.270 1.787 0.579
Ophiactidae 0.044 0.938 -0.513
Paguridae 0.245 -0.188 0.568
Pinnotheridae 0.244 -0.605 -1.289
Porcellanidae -1.301 -0.181 0.164
Pyramidellidae -1.971 0.796 0.236
Solemyidae 0.045 1.711 -0.769
Solenidae 0.267 -0.117 0.900
Tellinidae 0.248 0.157 -0.328
Ungulinidae 0.109 0.428 -0.252
Xanthidae -2.660 -0.380 0.230
Sturgeon-Fall 2001 relocations 0.219 0.506 0.479
Sturgeon-Spring 2002 relocations 0.095 -0.368 0.195



































83015' 83010' 8305'


Figure 4. Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee
River estuary, Florida, during the fall of 2001 (November 7 through
December 19) and the spring of 2002 (March 14 through April 17). Thirteen
of the eighteen tagged Gulf sturgeon, eight in the fall of 2001 and ten in the
spring of 2002, were relocated (one position per day is represented) for a total
of 39 relocations.


















29020' 2902
A

FO





G -
H


M1
29015 29015'



0 4 Miles


83015' 83010' 8305'

Figure 5. Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee
River estuary, Florida, during the fall of 2001 (November 7 through
December 19). Eight out of the eighteen originally tagged Gulf sturgeon,
seven males and one female, were relocated (one position per day is
represented) for a total of 10 relocations (filled circles). The letter nearest to
each relocation point is the unique fish identifier assigned to the specific
sturgeon that was relocated (see Table 3).































29o15' B G C v 2915'
H *
G F
Q Q

0 3 Miles C.


83015' 83010' 835'

Figure 6. Positions of all relocated ultrasonic-tagged Gulf sturgeon in the Suwannee
River estuary, Florida, during the spring of 2002 (March 14 through April 17).
Ten of the eighteen originally tagged Gulf sturgeon, five males and five
females, were relocated (one position per day is represented) for a total of 29
relocations (filled circles). The letter nearest to each relocation point is the
unique fish identifier for the specific sturgeon that was relocated (see Table
3).



















29020' \ 29020'

Alligator Pass






2915' 2915,



0 5 Miles


83015' 83010' 8305'

Figure 7. Patterns of relocations of Gulf sturgeon (n = 39) in the Suwannee River
estuary during the fall of 2001 and the spring of 2002 calculated as utilization
distributions (UD)(95%, 80%, and 50%) using a fixed kernel method with a
least-squares cross-validation smoothing parameter (ArcView 3.2). Solid gray
represents the 50% UD; vertical stripes represent the 80% UD; and horizontal
stripes represent the 95% UD. The asterisks represents one sturgeon
relocation outside the delineated Main Suwannee tracking area (boxed
perimeter).





































83015' 83010' 8305'


Figure 8. Relocation positions for two individual tagged Gulf sturgeon, Fish F and Fish
M, in the Suwannee River estuary, Florida. Fish F is illustrated by open
circles and Fish M is illustrated by filled circles. The number closest to each
relocation position in the figure is the date when that specific relocation was
made.





































83015' 83010' 8305'


Figure 9. Relocation positions (filled circles) for Fish G in the Suwannee River estuary,
Florida. The number closest to each relocation position in the figure is the
date when that specific relocation was made.





































83015' 83010" 8305'


Figure 10. Relocation positions (filled circles) for Fish H in the Suwannee River estuary,
Florida. The number closest to each relocation position in the figure is the date
when that specific relocation was made.





































83015' 83010' 8305'


Figure 11. Relocation positions (filled circles) for Fish C in the Suwannee River estuary,
Florida. The number closest to each relocation position in the figure is the date
when that specific relocation was made.

































29016 29016'
03-16-02


0 3 Miles


83010' 8308' 8306'


Figure 12. Relocation positions (filled circles) for Fish Q in the Suwannee River estuary,
Florida. The number shown closest to each relocation position in the figure is
the date when that specific relocation was made.



















29020- 29020'

Alligator Pass












0 6 Miles


8315' 83010' 8305'

Figure 13. Patterns of relocations of tagged Gulf sturgeon (n = 10) in the Suwannee
River estuary during the fall of 2001 calculated as utilization distributions
(UD)(95%, 80%, and 50%) using a fixed kernel method with a least-squares
cross-validation smoothing parameter (ArcView 3.2). Solid gray represents
the 50% UD; vertical stripes represent the 80% UD; and horizontal stripes
represent the 95% UD.




































Figure 14. Patterns of relocations of Gulf sturgeon (n = 29) in the Suwannee River
estuary during the spring of 2002 calculated as utilization distributions
(UD)(95%, 80%, and 50%) using a fixed kernel method with a least-squares
cross-validation smoothing parameter (ArcView 3.2). Solid gray represents
the 50% UD; vertical stripes represent the 80% UD; and horizontal stripes
represent the 95% UD.









Molluscs
Echinoderms -


Brachiopods


I


~iili~olot/


Figure 15. Total relative abundance of all invertebrate taxa by phylum, except annelids,
from all 28 cores collected in the Suwannee River estuary, Florida, April 22
through May 9, 2002.














Molluscs
Arthropods










Echinoderms
Brachiopods


Figure 16. Total relative biomass of all invertebrate taxa by phylum, except annelids,
from all 28 cores collected in the Suwannee River estuary, Florida, April 22
through May 9, 2002.














30



25

.1,
.20
E


S30

25

cn 20

15

10


0 $

0* 0











000
S









o o


So s

0 0o
0
o


Nov Dec Jan Feb Mar Apr
Month


Figure 17. Temperature and salinity at relocation positions of Gulf sturgeon in the
Suwannee River estuary. Temperature and salinity were measured 10 cm
above the bottom. Filled circles (n = 38) represent temperature and open
circles (n = 36) represent salinity. Measurements were grouped by week.







76


2X
5Z
2Y 1
4Z
6Z
3X --
4X
5Y
3Z
9Z
2Z
8Z
Sl 2
3Y
4Y
S2
5X
7X
7Y
6X
s3 3
9X
S4
8X
8Y
9Y
6Y 4
7Z


Figure 18. Percent sediment size type (Very Fine Sand, Sand, Small Shell, and Oyster
Shell) clustered by benthic core site using the Ward's minimum variance
method (PC-ORD 4). Sediment was collected from benthic cores taken from
the Suwannee River estuary, Florida, from April 22 through May 9, 2002.
Bold numerals represent the four unique clusters identified using this
technique (see Table 9).



















29020' 29020'









29015' 2 29015'

1
0 6 Miles


83015' 83010' 8305'

Figure 19. Relocations of Gulf sturgeon (filled circles) in the Suwannee River estuary,
Florida, in the fall of 2001 (November 7 through December 19) and spring of
2002 (March 14 through April 17) in relation to sediment type from 28 core
sites in the Suwannee River estuary. Thirteen out of eighteen tagged sturgeon,
eight individuals in the fall of 2001 and ten individuals in the spring of 2002,
were relocated (one position per day is represented) for a total of 39
relocations. Clustering was completed using the Ward's minimum variance
method (PC-ORD 4). Core sites were interpolated to fill the Main Suwannee
tracking area (outer boxed perimeter) using a Thiessen polygon interpolation
method and grouped according to the cluster (ArcView 3.2). Bold numerals
represent the four unique clusters identified using this method (see Figure 18).







78


2X
8Z 1
3X
4X 2
6Y
2Y
9X
S3 3
3Y
5Y
9Y
8Y
2Z
6X
4Z
5Z
5X
7X
8X
S4 4
3Z
4Y
S1
7Y
7Z
6Z
9Z
S2


Figure 20. Total biomass of all invertebrates (excluding polychaetes) clustered by
benthic core site using the Ward's minimum variance method (PC-ORD 4).
Cores collected from all 28 sites (on the Y-axis) in the Suwannee River
estuary, Florida, from April 22 through May 9, 2002, were used for the
analysis. Bold numerals represent the four unique clusters identified using this
technique (see Table 13).



















29020' 0 rS 290 20'

4






29015' 1 29015'



0 6 Miles


83015' 83010' 8305'

Figure 21. Relocations of all Gulf sturgeon (filled circles) in the Suwannee River estuary,
Florida, in the fall of 2001 (November 7 through December 19) and spring of
2002 (March 14 through April 17) in relation to total invertebrate biomass
from 28 core sites in the Suwannee River estuary. Thirteen out of eighteen
tagged sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were
relocated (one position per day is represented) for a total of 39 relocations.
Clustering was completed using the Ward's minimum variance method (PC-
ORD 4). Sites were interpolated to fill the Main Suwannee tracking area
(outer boxed perimeter) using a Thiessen polygon interpolation method and
grouped according to cluster (ArcView 3.2). Bold numerals represent the four
unique clusters identified using this method (see Figure 20).







80


2X
9x
9Y
S3
5X
6X | 2
S4
7X
3X
8Y
7Y
5Y-- 3
4X
S1
S2
2Y
3Y 4
4Y
6Z
7Z
2Z
3Z
8X
5Z
8Z 5
6Y
4Z
9Z


Figure 22. Numerical abundance of the Gulf sturgeon's main prey resources: amphipods
(Ampelisca), brachiopods (Glottidiapyramidata), and brittle stars
(Amphiuridae and Ophiactidae), clustered by benthic core site using the
Ward's minimum variance method (PC-ORD 4). Prey invertebrates were
collected in the Suwannee River estuary, Florida, from April 22 through May
9, 2002. Prey resource abundances were logio(x +1) transformed to reduce
variation between the invertebrate groups. Bold numerals represent the five
unique clusters identified using this method (see Table 15).



















29020' 4 -290 20'

5 42


5 2
4 5
3

29015' 29015'


0 6 Miles


83015' 83010' 8305'

Figure 23. Relocations of Gulf sturgeon (filled circles) in the Suwannee River estuary,
Florida, in the fall of 2001 (November 7 through December 19) and the spring
of 2002 (March 14 through April 17) in relation to the abundance of their
main prey resources: amphipods (Ampelisca), brachiopods (Glottidia
pyramidata), and brittle stars (Amphiuridae and Ophiactidae) collected from
28 core sites in the Suwannee River estuary. Thirteen out of eighteen tagged
sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were relocated
(one position per day is represented) for a total of 39 relocations. Clustering
was completed using the Ward's minimum variance method (PC-ORD 4).
Sites were interpolated to fill the Main Suwannee tracking area using a
Thiessen polygon interpolation method and grouped according to cluster
(ArcView 3.2). Bold numerals represent the five unique clusters identified
using this method (see Figure 22).







82


2X
5Y
7Z
2Z
4Z
7X
6Z 1
5Z
8Z
6Y
6X
8X
S4
2Y
9X
3Z
S1
4Y
7Y
S2
5X
9Z
3Y
9Y 3
S3
8Y
3X| 4
4X


Figure 24. Total biomass of the Gulf sturgeon's main prey resources as seen in stomach
contents: amphipods (Ampelisca), brachiopods (Glottidiapyramidata), and
brittle stars (Amphiuridae and Ophiactidae), clustered by benthic core site
using the Ward's minimum variance method (PC-ORD 4). Prey invertebrates
were collected in the Suwannee River estuary, Florida, from April 22 through
May 9, 2002. Bold numerals represent the four unique clusters identified
using this method (see Table 17).



















29020' *3 29020'








29015' 29015'


0 6 Miles


83015' 83010' 8305'

Figure 25. Relocations of Gulf sturgeon (filled circles) in the Suwannee River estuary,
Florida, in the fall of 2001 (November 7 through December 19) and spring of
2002 (March 14 through April 17) in relation to the total biomass of their
main prey resources: amphipods (Ampelisca), brachiopods (Glottidia
pyramidata), and brittle stars (Amphiuridae and Ophiactidae) collected from
28 core sites in the Suwannee River estuary. Thirteen out of eighteen tagged
sturgeon, eight in the fall of 2001 and ten in the spring of 2002, were relocated
(one position per day is represented) for a total of 39 relocations. Clustering
was completed using the Ward's minimum variance method (PC-ORD 4).
Sites were interpolated to fill the Main Suwannee tracking area using a
Thiessen polygon interpolation method and grouped according to cluster
(ArcView 3.2). Bold numerals represent the four unique clusters identified
using this method (see Figure 24).







84


2X
4Z
9Y 1
4Y
6Z
7Z
2Z
6Y
8X
9Z
3Z 2
S4
5X
5Z
6X
7X
8Z
9X
S3
2Y
8Y
3Y 3
5Y
7Y
3X
4X 4
S1
S2


Figure 26. Abundance of brachiopods Glottidiapyramidata, clustered by benthic core
site using the Ward's minimum variance method (PC-ORD 4). Brachiopods
were collected from the Suwannee River estuary, Florida, from April 22
through May 9, 2002. Brachiopod abundances were logio(x +1) transformed
to reduce the influence of very high abundances. Bold numerals represent the
four unique clusters identified using this method (see Table 19).



















29 20' 2 4 290 20'




2 2


3\

29015' 29015'


0 6 Miles


83015' 83010' 8305'

Figure 27. Relocations of Gulf sturgeon (filled circles) in the Suwannee River estuary,
Florida, in the fall of 2001 (November 7 through December 19) and spring of
2002 (March 14 through April 17) in relation to brachiopod abundance
collected from 28 core sites in the Suwannee River estuary. Thirteen out of
eighteen tagged sturgeon, eight in the fall of 2001 and ten in the spring of
2002, were relocated (one position per day is represented) for a total of 39
relocations. Clustering was completed using the Ward's minimum variance
method (PC-ORD 4). Sites were interpolated to fill the Main Suwannee
tracking area using a Thiessen polygon interpolation method and grouped
according to cluster (ArcView 3.2). Bold numerals represent the four unique
clusters identified using this method (see Figure 26).











83015'


83010'




i iiiiiiii iiiiiiiiiiiiiiiiii:








.. 4 '
Ffl +




S


-=4

/y~



0@


8305'


N
N


I 2 0 -25
I l 25 -50
| 50 100
1H 100-200
1 200- 382


~-i~ ~r








I54~


0 2 Miles


83015'


83010'


2920'














29'15'


8305'


Figure 28. The distribution of ultrasonic-tagged Gulf sturgeon (filled circles) in relation
to the distribution of brachiopods (abundance/m2) in the Suwannee River
estuary. Thirteen out of eighteen tagged sturgeon, eight in the fall of 2001 and
ten in the spring of 2002, were relocated (one position per day is represented)
for a total of 39 relocations. Brachiopods were collected from April 22
through May 9, 2002. Interpolation of brachiopod density (abundance/m2)
between sites was completed using an inverse distance weighting method in
ArcView 3.2.


29020'














29015'


w I







87


2X
5Y
7Z
2Z
4Z
7X
6Z 1
5Z
8Z
6Y
6X
8X
S4
2Y
9X
3Z
S1
4Y
7Y
S2
5X
9Z
3Y
9Y 3
S3
8Y
3X| 4
4X


Figure 29. Biomass of brachiopods Glottidiapyramidata, clustered by benthic core site
using the Ward's minimum variance method (PC-ORD 4). Brachiopods were
collected from the Suwannee River estuary, Florida, from April 22 through
May 9, 2002. Bold numerals represent the four unique clusters identified
using this method (Table 21).