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Influence of High-Resolution Spatial Information on Resource Exploitation: An Example from Angler Impacts on Artificial Reefs


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INFLUENCE OF HIGH-RESOLUTION SPATIAL INFORMATION ON RESOURCE EXPLOITATION: AN EXAMPLE FROM ANGLER IMPACTS ON ARTIFICIAL REEFS By STEPHEN J. LARSEN 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 2005

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Copyright 2005 by Stephen J. Larsen

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iii ACKNOWLEDGMENTS I thank my advisor Dr. William J Lindberg for introducing me to the Gulf of Mexico ecosystems and encouragement to s ee and think about the big picture. This research and the completion of my graduate career would not have been possible without his guidance, optimism, and perspective on the project at hand. I thank Dr. Debra Murie for serving on my committee and for her guidance and input th roughout my graduate experience. I thank Dr. Tom Frazer for serv ing on my committee as well as providing perspective on what the important things are and not to lose sight of them. Enormous thanks go out to Dr. Ken Portier for his help with the statistical aspects of this project. Thanks also to Dr. Mike Allen for statistical guidance and the encouragement to complete the degree for there are bigger and be tter things following graduation. Special thanks go to lab-mate s Doug Marcinek, Mark Butler, and Brian Nagy who collectively welcomed me into the Lindberg Lab, made my transition to graduate school easy and provided a great sounding board for ideas, discussions, and frustrations. Additional thanks go to gradua te students Rick Kline, Mark Rogers, and Paul Anderson for always being willing to give time even when they had none to give. In fact every graduate student who passed thr ough the carrels of the Fisheries and Aquatic Sciences Department from August, 2001, thr ough Fall, 2005, contributed to a great work environment and community of friends that is regrettably so temporary in nature.

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iv TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iii LIST OF TABLES...............................................................................................................v LIST OF FIGURES...........................................................................................................vi ABSTRACT......................................................................................................................v ii CHAPTER 1 INTRODUCTION........................................................................................................1 2 METHODS...................................................................................................................9 Experimental System....................................................................................................9 Study Organism..........................................................................................................10 Sources of Data...........................................................................................................11 Suitability of Data.......................................................................................................12 Experimental Design..................................................................................................13 Statistical Analyses.....................................................................................................13 3 RESULTS...................................................................................................................16 Legal Gag....................................................................................................................16 Pre-publication Time Period (Initial Conditions)................................................16 Transition from “Pre” to “Acute” Time Periods.................................................17 Within “Acute”....................................................................................................17 Transition from “Acute” to “Chronic”................................................................18 Within “Chronic”.................................................................................................18 Sub-Legal Gag............................................................................................................19 4 DISCUSSION.............................................................................................................27 REFERENCES..................................................................................................................37 BIOGRAPHICAL SKETCH.............................................................................................44

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v LIST OF TABLES Table page 1. Type 3 tests of fixed effects for legal gag......................................................................21 2. Type 3 tests of fixed effects for sub-legal gag...............................................................22

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vi LIST OF FIGURES Figure page 1. Design of the Suwannee Regional Reef System............................................................15 2. Pre-publication distribution of legal ga g grouper on the SRRS. Data are drawn from not-to-be-published arrays due to the influence of pre-publication perturbations on to-be-published arrays...................................................................23 3. Chronology of impacts to legal gag on 16cube arrays of the SRRS by array architecture and publication status...........................................................................23 4. Chronology of impacts to legal gag on four-cube arrays of the SRRS by array architecture and publication status...........................................................................24 5. Abundance of legal gag per array within the “acute” pe riod by array architecture and publication status...............................................................................................24 6. Abundance of legal gag per array within the “chronic” period by array architecture and publication status...............................................................................................25 7. Abundance of sub-legal gag per array, by ar ray architecture and publication status, averaged across all time periods...............................................................................25 8. Abundance of sub-legal gag per array, by array architecture on (A) published and (B) unpublished arrays.............................................................................................26

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vii Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science INFLUENCE OF HIGH-RESOLUTION SPATIAL INFORMATION ON RESOURCE EXPLOITATION: AN EXAMPLE FROM ANGLER IMPACTS ON ARTIFICIAL REEFS By Stephen J. Larsen December 2005 Chair: William J. Lindberg Major Department: Fisherie s and Aquatic Sciences Exploitation of natural resources is dependent on knowing where to find those resources. Increasingly speci fic and detailed informati on regarding the location and relative value of many resour ces is being continually de veloped by rapidly advancing technologies in remote sensing. It is gene rally assumed that such information allows more efficient and directed exploitation of those resources. I evaluated impacts of the public release of deta iled geographic information regard ing artificial reefs designed for gag grouper ( Mycteroperca microlepis ). Reefs were construc ted of concrete cubes approximately 90 cm on a side. Size of reef patches (4-cube and 16-cube, small and large respectively), and distances among patches (25 m and 225 m), were examined. Approximately half of the reef locations were published to the ang ling community. Reefs were monitored from two years prior to publication to two year s-post publication and again six to eight ye ars post-publication.

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viii Impacts on published reef arrays were highest on large, closely spaced reef arrays, and least on small, widely spaced reef arrays. In contrast to pre-publication trends, large reef patches, once published, no longer held more legal gag (>508 mm) than small patches. Six to eight years after publicati on sub-legal gag (<508 mm) were reduced on the largest, most closely spaced arrays, indi cating that these reefs received the highest fishing effort. Large unpublished reefs as well as small, widely spaced reefs showed effects of discovery by anglers in the period six to eight years after other reefs in the study system were made publicly known. The disclosure of locations of previously untargeted, high-quality habitat led to imme diate exploitation of legal gag, with the exception of apparent refuges of small habi tat patches, which are inherently more difficult to locate and to fis h. Resource managers should take into account the improved efficiency of exploitation made possibl e by the collection and dissemination of highresolution geographic habitat data.

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1 CHAPTER 1 INTRODUCTION Accurate and rapid collecti on of spatially explicit da ta regarding the natural environment has been made possible over recent decades by the development of new technologies. Advances in satellite imagi ng and sensing systems as well as sonic and laser technologies are providing unprecedented detail and information. The utility of high-resolution spatial data to both resource managers and user groups has been clear. It has made possible the quantific ation of changes in land use and land cover to describe processes such as deforestation and dese rtification (Pamo, 2004; Leimgruber et. al., 2005) and shoreline changes (Mor ton et. al., 2005) with much greater accuracy than prior techniques, provided for far more proficient and directed use of natural res ources (Pickrill and Todd, 2003), and has opened lines of scie ntific inquiry prev iously limited by the technology available (Wright, 1999; Andersen et. al., 2005; Leimgruber et. al., 2005). In the sea, detailed surveys have be en conducted through the use of multi-beam sonar systems (Verlaan, 1997; Pickrill a nd Todd, 2003) as well as the LIDAR (Laser Imaging Detection and Ranging) optical sy stem (Kincade, 2003). Coupled with Geographic Positioning Systems (GPS), data can be placed very precisely in a spatial context. Such detailed information has already demonstrated its utility in the management, exploration, and understanding of the marine environment. In coastal environments, decisions regarding location of sewage outfalls as well as cable and pipeline routes have been well founded (Pickri ll and Todd, 2003). Side-scan sonar has been used to identify mineral deposits on the o cean floor (Lee and Kim, 2004) and investigate

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2 the geo-physical properties of hydrothermal vents and area s of sea-floor spreading (Wright, 1999). In fisheries, LIDAR has been combined with vide o technology for the remote sensing of schools of capelin ( Mallotus villosus ) and zooplankton densities (Brown et. al. 2002). Detailed maps were created of Brown’s Bank in the Northern Atlantic, which were then coupled with biol ogical data to identify key scallop habitats (Kostylev et. al., 2003). As a consequence, commercial trawlers were able to reach quotas in as little as one quarter the time while avoiding fragile or unproductive regions (Pickrill and Todd, 2003). The availability of such detailed geogra phic data is clearly a boon to resource managers and those working in the natural environment. Mack (1990) noted, however, that there are unintended uses of new technol ogies that may only become apparent once a program is well underway. For example, fisher y resources are inherently patchy in space, and detailed geographic information collected to other ends has the potential to facilitate their exploitation. In the example of the commercial scallop fishery on Brown’s Bank (Kostylev et. al., 2003; Pickrill and Todd, 2003), a quota limited the harvest. New technologies provided informati on facilitating more efficien t harvest without increasing the overall effect on the fishery, and possibly minimized impacts to benthic habitats by reducing the area trawled. Had there been no quota, continued effi cient and directed efforts could have led to much greater yields and thus pot ential overexploitation in the fishery. The development of informati on increasing the potential for efficient exploitation of natural resour ces, if not coupled with pr oper management strategies, creates the possibility of over-e xploitation of those resources.

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3 Like the scallop, many marine fishery species are associated with specific habitat types. The current efforts in sea-floor mapping hold the potential of identifying and describing those habitats in great detail, l eading to far better unde rstanding of population distributions and identification of essential fish habitats. While clearly useful to managers, to date, there are few documented examples of how fishermen use detailed geographic information of fish habitat. Id entification of densel y populated habitat among recreational fishermen is commonly achieved through large expenditu res of effort in exploring new areas and searching with the limited bottom mapping information and technologies available to the recreational sector. Due to the investment in locating fishing sites, once found, such areas are rare ly made public. Although maps are created and bathymetric data are availa ble to recreational anglers, th ey are typically of coarse scale and limited scope. The Ideal Free Distribution (IFD), as applie d to the dist ribution of angling effort (Walters and Martell, 2004), predicts that effo rt will be directed to the most profitable fishing grounds. One assumption of the IFD is complete knowledge of fishing grounds and the relative profitability of each. Increa se in awareness of available fishing grounds, as is made possible by detailed bottom mappi ng, will likely lead to a distribution of angling effort closer to that predicted by the IFD. The predicted consequences are an increase in catch-per-unit-effo rt (CPUE) in the short-term, and hyper-stability in the longterm as detailed geographic information facil itates exploitation in the face of declining stocks. Due to the expanse of marine environmen ts and limited ability of recreational anglers to accurately perceive the sea floor, habitat extent is likely a key factor in

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4 determining its probability of discovery. Small, isolated habitat patches that support dense local populations of fish are difficult to locate by conventional means, rarely shared if they are discovered, and are likely key habi tat features providing refuge for targeted marine species. The uncontrolled dissemina tion of fine-scale bathymetry could reveal such locations in detail, leading to better-directed and more efficient exploitation of stocks that are patchy in space. The importance of such refuges is largely unknown, but is potentially critical in the maintenance of a viable fishery. The impact s of both recreational and commercial fishing on populations and assemblages of marine fi sh have been well documented (Haedrich and Barnes, 1997; Wantiez et. al., 1997; Bi anchi et. al., 2000; Roberts et. al., 2001; Bremner et. al., 2003; Coleman et. al., 2004). Fishing generally leads to fewer and smaller fish of the targeted species (Haed rich and Barnes, 1997; Grandcourt, 2003) as well as reduced overall diversity (Albaret and Lae, 2003; Le y et. al., 2002). Protection from fishing, in some cases, has reversed these trends (Roberts, 1994; Wantiez et. al., 1997) and resulted in increased abundance and si ze of targeted fish as well as increased biodiversity in protected areas. Refuges provide fish the oppor tunity to become older and larger. Such individuals are of great importance to the welf are of a fishery (Birkeland and Dayton, 2005). For some species, larger an d older individuals have been shown to have exponentially higher f ecundity (Berkeley et. al., 2004a ) and to produce healthier, faster-growing larvae (Conover and Munch, 2002; Berkeley et. al., 2004b), as well as preserving genetic diversity (Hauser et. al., 2002). As large-scale sea-floor mapping programs are relatively new, studies of such natural, small, isolated, but high quality, habitat features are rare. The use of artificial

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5 reef structures to create such locales provides the oppor tunity to control for habitat features (size, shape, and di stribution) that may influence the resulting assemblage of species as well as the exploitation of the resident species by fishers. The specific characteristics of artificial habitat along with reef placement (Coll et. al., 1998) strongly influence the resulting asse mblage of marine life. There are two characteristics of artificial re ef use by marine fish that ha ve been widely studied: as shelter and as a food source. Available refuge has been demonstrated to be the dominant structuring influence on the species resident on a reef (Williams and Sale, 1981; Doherty and Sale 1985; Sweatman, 1985; Hixon and Beets, 1989; Eklund, 1997; Lindberg in press) although resident species clearly use the reef as a forage base (Herrera et. al., 2002; Szedlmayer and Lee, 2004). Many top-level predators are transien t groups (e.g., jacks, sharks, tunas, mackerels) and would be less-f requently observed at artificial reefs despite their potential for playing a major role in th e structuring processes of the resident fish assemblage (Bohnsack et. al., 1994; Carr et. al., 2002). The use of artificial reefs as refuge is de pendent on the shelter characteristics of the structure provided. Many studi es have investigated the effe cts of reef size and design on resulting fish assemblages. Several genera l trends have been observed. Larger reef structures support higher abunda nces of fish (Rountree, 1989; Lindberg and Loftin, 1998) though not necessarily at higher densities (p er unit reef area) (Bohnsack et. al., 1994; Lindberg and Loftin, 1998). Bohnsack et. al. (1994) found that although there are lower densities at larger reefs, the resident fish ar e larger on average than on smaller reefs. In contrast, Lindberg et. al (in press) observed hi gher growth rates by gag, Mycteroperca microlepis on smaller artificial reef patches. Th ese patterns are likely dependent on the

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6 species and system being studied. Size of refuges within a reef has been shown to positively influence the abundance of fish suite d to the size of refuge provided (Frazer and Lindberg, 1994; Hixon and Beets, 1989; Hart 2002). Fish tend to prefer openings close to their own body size (Shulman, 1984). Within reefs, higher habitat complexity increases diversity of the resul ting assemblage as adequate shelter is provided for a larger range of species (Charbonne l et. al., 2002; Sherman et. al ., 2002; Gratwicke and Speight, 2005). Although resident species also use the reef and surrounding area as a forage base (Herrera et. al., 2002; Szedlmayer and Lee, 2004), several studies ha ve concluded that refuge is the over-riding factor determining a bundance of resident fish on artificial reefs (Ecklund, 1997; Lindberg et. al. in press). For recreational anglers, artificial r eefs are widely-known and publicized, easily locatable angling sites. In public survey s, 6.4% (McGlennon and Branden, 1994) to 87% (Ditton and Graefe, 1978) of angl ers reported fishing on artificia l reefs. The lower end of the spectrum resulted in a fishing intensit y (angler hours/unit area) 92-171 times greater than observed on natural substrates (McGlennon and Branden, 1994). While expectations of high catch ra tes are a motivating factor fo r selecting artificial reefs (Milon, 1989) only 5 of 27 comparisons by McGlennon and Branden (1994) yielded significantly higher catch rate s on artificial habitats, and these were all for pelagic species. Solonsky (1985) demonstrated the si gnificant impact that anglers can have on recreationally targeted game fish on an artifici al reef in Monterey Bay. One central reef amidst several others was marked for recreati onal fishing. After three years, there were significantly fewer rockfish on the marked reef relative to the unmarked reefs surrounding it. Furthermore, tagged fish on the surrounding reefs were observed to move

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7 onto the marked reef, but none were observed leaving the marked reef, demonstrating the function of a known artific ial reef to attract fish thus increasing their vulnerability to fishing. Turpin and Bortone (2002), who observe d artificial reefs before and after they were displaced by hurricanes, also observed a significant increase in lengths of gag, and red snapper, Lutjanus campechanus on these reefs following displacement as anglers no longer knew their locations. Th e use of artificial reefs in the study reported here offers the additional dimension of high at traction for recreational anglers. The purpose of this study was to test how the public release of detailed location information regarding patchy habitat impacted the standing stock of gag, a dominant reefassociated, recreationally-target ed species. The specific objec tives were: (1) to determine how publication of reef locations to angler s differentially affected abundances of both legal and sub-legal gag across di fferent reef architectures (siz es and spacings), and (2) to determine the impacts of angling over a br oad time-scale, including the discovery and exploitation of unpublished reef locations. This evaluation of angling impacts as a function of habitat patchiness and location information provides fishery managers with experimental results pertinent to the manage ment of fisheries in light of the everincreasing efficiencies that anglers garner through ne w and developing technologies. Publication was predicted to l ead to rapid reductions of legal gag. A refuge effect on more-widely spaced patches was predicted as these are mo re difficult to fish as a single unit. Angling impacts were predicted to be greatest on 16-cube arrays as anglers are likely to favor these under the conception th at larger habitat patches hold more fish. Discovery of unpublished arrays was expected to be a function of both patch size and spacing. Larger and more-widely spaced patc hes provide the greatest probability of

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8 encounter for searching anglers. Discovery of a single patch should l ead to discovery of the entire array as anglers were aware of the reef layouts within the experimental system. Several mechanisms likely affect sub-legal gag abundance. Compensatory responses to predicted decreases in legal gag abundances would lead to an increase in sub-legal gag abundance. Induced immigration and mortalit y from catch and release would lead to declines in sub-legal gag abundance. Large, cl osely-spaced arrays were predicted to have the highest fishing effort, thus they were e xpected to demonstrate the relative importance of these mechanisms.

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9 CHAPTER 2 METHODS Experimental System The Suwannee Regional Reef System (S RRS) was constructed from 1990 to 1993 in the northeastern Gulf of Mexico, approximately 20-25 km from the mouth of the Suwannee River (Figure 1A). The building bl ocks of the SRRS were 89 cm x 89 cm x 89 cm concrete cubes with 60 cm diameter cylindrical horizontal passages through the centers and 10 cm diameter, horizontal, right -angle tunnels through each of the eight corners (Figure 1B). Cubes were arranged in either 4-cube or 16-cube square reef patches, such that central passages all run in the same direction. Patches were arranged hexagonally, and were spaced 25, 75 or 225 m apart, constituting a reef array (Figure 1B). Reef arrays were spaced one to two km apart along the 13 m depth contour. Twenty-two arrays comprise the entire S RRS, which was designed as a 3 x 2 factorial experiment with three spacing treatments (25m, 75m, 225m) and two patch size treatments (4-cube and 16-cube). The SRRS was twice affected by perturba tions in its initial years. In 1992, locations of four arrays we re inadvertently published. In 1995, all fish on the five southernmost arrays were eliminated by a red ti de event. This fish-kill effectively reset the fish colonization process on those ar rays. Two arrays were both published inadvertently and experienced the fish-kill. In November of 1996, locations of two to three arrays per treatment group were published for access by the general public. No locations of the 75 m spaced arrays were

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10 published and thus the 75 m treatment wa s excluded from this study. The early perturbations and requirements of other on-going research projects warranted restrictions on randomization when selecting arrays fo r publication, e.g. inadvertently published arrays were assigned to the ‘published’ treatment. Study Organism Gag, Mycteroperca microlepis is a dominant reef-associat ed, demersal fish species in the Western Atlantic ranging from New E ngland to Brazil, incl uding the Gulf of Mexico (McErlean, 1963). As protogynous he rmaphrodites, female gag mature at 3-6 years old and 538 to 795 mm TL (Hood and Sc hlieder 1992; Harris and Collins 2000). In two studies, no males younger than five or smaller than 875 mm TL were observed (Hood and Schlieder 1992; Harris and Collins 2000). By age 11, males comprised 50% of the age class. Transition from female to male is hypothesized to be socially mediated (Koenig et. al. 1999; Coleman et. al. 2002) but is debated (Kenchington, 1999). Gag reach sizes between 1100 and 1200 mm and ages ranging into the early twenties (Hood and Schlieder 1992; Collins et. al. 1998). Gag form spawning aggregations of 10’s to 100’s of individuals (Coleman et. al., 1996). Aggregations have been observed al ong the shelf edge break in the Northwest Gulf of Mexico in 50-120 m (Coleman et. al. 1996; Koen ig et. al., 1999), on deep (70100 m) reefs off the Atlantic coast of Florid a (Gilmore and Jones, 1992), and have been recently reported on the Campeche Bank, Yucat an, Mexico (Brule et. al., 2003). Gag spawn from late December through April wi th peak spawning in February and March (Hood and Schlieder 1992; Collins et. al. 1998). Currents carry gag larvae inshore where they settle in seagrass beds and oyster ba rs (Ross and Moser, 1995). Average larval duration is approximately 43 days (Keener et. al. 1988). Gag spend their first summer

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11 growing in inshore habitats where their di et is composed primarily of crustaceans (Bullock and Smith 1991; Weaver 1996). In the late summer and fall, gag move to deeper water and take up residency on near-s hore reefs and live-bo ttom where their diet shifts to decapod crustaceans and fishes (Bu llock and Smith 1991; Weaver 1996). It is in these habitats that gag reach legally harvestabl e size and are first targ eted by fishers. Gag continue to grow and mature in these e nvironments before moving to spawning grounds as mature adults. The natural annual mort ality rate is unknown but is assumed to be M=0.15 for stock assessment purposes (Turner et al. 2001). It is du ring their transition across the shallow continental shelf that juve nile to sub-adult pre-reproductive females take up residency on the SRRS Sources of Data Gag present on each SRRS patch were counted once each Summer from 1995 to 1998 and 2002 to 2004 by trained SCUBA divers (see Lindberg et. al., in press for details). Types of data collected changed over the years of sampling as the research questions being addressed changed. I worked with a historical data set (1995 to 1998) and participated in data collection du ring the 2002 to 2004 period. From 1995 to 1996 the total number of gag on each patch reef were counted and divers visually estimated the length of the largest and smallest gag as well as the average size of gag. In 1997 and 1998, counts were divided into total number of legal ( >20” or 508 mm) and sub-legal (<20” or 508 mm) gag. In 2002 through 2004, ga g were individually assigned to 10 cm size groups. The 50-59 cm size group was fu rther divided into gag from 50-55 cm and 56-59 cm in order to determine the number of legal and sub-legal gag on a patch. This coincided with an increase in the legal size of recreationally harvestable gag from 20” (508 mm) to 22” (559 mm) that occurred on J une 19, 2000 (Turner et. al., 2001). For this

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12 investigation, all data were converted to counts of legal and sub-legal gag by array. Legal and sub-legal counts we re estimated for 1995 and 1996 from percentages of legal and sub-legal gag observed on unpublished arrays of the same architecture in 1997. This is based on a necessary assumption that the proportions of legal and sub-legal gag on patches of like architecture and presumed level of fishing effo rt is consistent over time (1995-1997) and space (among unpublished arrays). These approximations were further adjusted based on the size estimates for the la rgest and smallest gag (i.e., if the largest gag observed was smaller than the legal limit, all gag were considered sub-legal). Patch reef counts were summed for each array, as th e arrays rather than the patches are the proper replicates for this study. Suitability of Data Preliminary analyses were conducted to establ ish the suitability of data to be used. Reef arrays were constructed from 19901993. Within arrays, data from 1995 and 1996 were compared for significant differences. N one were found and thus variable reef age was determined not to be a significant fact or influencing gag abunda nces. In 1995 a fishkill event eliminated all fish on the five southern-most reef arrays. The fish-kill was investigated as a treatment effect within reef architectures. Data were excluded from the final model for all architecture/year combinations in which the fish-kill treatment was significant. This resulted in th e exclusion of data from all fish-killed arrays in 1995. In 1996 legal counts on four-cube arrays were cons idered recovered and included in further analyses. Analysis indicated all affected arrays had recovered by 1997. In 1992, several array locations were inadverten tly published. Due to low re plication and the impacts of the fish-kill, I was unable to evaluate this effect.

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13 Experimental Design Three variables were investigated in a re peated measures 2 x 2 x 2 x 3 factorial design for their effects on gag abundance on the SRRS: patch spacing (25 m or 225 m between patches within an ar ray), patch size (4 or 16 cubes per patch), publication of locations for public fishing (published or not), and time period. Annual counts were nested within three different time periods (time relative to th e publication of array locations). “Pre” consists of data collected in 1995 a nd 1996, prior to publication. “Acute” consists of data collected in 1997 and 1998, the period immediately following publication. “Chronic” consists of data taken in 2002 th rough 2004, six to eight years following publication. Statistical Analyses All analyses were conducted independently on legal and sub-legal gag count data. To satisfy the assumptions of normality a nd homogeneity of variances, all count data were square root transformed. Data not excluded by the preliminary analyses were entered in a four-way repeatedmeasures, mixed-model Analysis of Vari ance (ANOVA) to determine significant interactions and main effects. Alternate correlation structures for the effect of year nested within period were tested, but none improve d the model over a zero-correlation model. The Kenward-Rogers method was used to estimate the degrees of freedom for the appropriate F-test for fixe d effects. Follow-up analyses were done by pair-wise comparisons of least square means provided fo r each treatment by the model. Residuals were plotted in a Q-Q plot and against predic ted values to examine model fit. Akaike’s information criterion as well as mean square error values were compared between treatment levels to investigate error structure in the model. All statistical analyses were

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14 performed in SAS version 8 (SAS Institute Inc. 2002, Cary, NC). An alpha value of 0.05 was used for determining statistical significance. Due to the low replication and thus low suspected power of these tests, the alpha value was not adjusted to maintain an experiment-wise error rate of 0.05.

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15 Figure 1. Design of the Suwannee Regional R eef System (A) Location of SRRS in the Big Bend region of Florida (i nset). (B) Design of a component artificial reef block and layout of an SRRS array.

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16 CHAPTER 3 RESULTS Legal Gag The four-way interaction of patch size, patch spacing, publication and time period was significant (p=0.0083, Tabl e 2) for legal-sized gag a bundances on the SRRS. The results of follow-up comparisons below e xplain this four-way interaction. The interaction is partitioned ch ronologically with steady-st ate comparisons within time periods and transitional comparisons between time periods. Mean square errors were examined between treatment levels and dete rmined not to be significantly different between levels of any treatment. Residua l analysis indicated good model fit. The significant model was run using untransformed data in order to generate least square means and error estimates for use in fi gures to better convey the results. Pre-publication Time Period (Initial Conditions) Arrays were not selected randomly for publ ication and thus there were pre-existing differences between arrays selected for the published and unpublished treatments. Arrays that experienced the fish-kill and those th at were inadvertently published were given priority as ‘published’ treatments in order to maintain a valid ‘unpublished’ treatment to compare against. To-be-published 4 x 225 m arrays had significantly fewer legal gag than their not-to-be-published counterparts even before th eir publicati on (p=0.0008). Beyond the perturbations, there was a di stributional pattern on the unpublished arrays dependent on the size and spacing of a rrays (Figure 2). Within spacing treatments, 16-cube arrays had a higher abundance of le gal gag than 4-cube arrays (25 m p=0.0002;

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17 225 m p=0.0009). Within 4-cube arrays, ther e was a higher abundance of legal gag on 225 m arrays than 25 m arrays (p=0.0314). Transition from “Pre” to “Acute” Time Periods The publication of array locations signif icantly impacted the abundances of legalsized gag for 16-cube arrays (Figure 3) for both spacing treatments (25 m p<0.0001; 225 m p<0.0001). Four-cube published arrays, how ever, did not change significantly following publication (25 m p=0.3378; 225 m p=0.3898), (Figure 4). There was a significant increase in legal gag abundan ce on unpublished 4 x 25 m arrays (p=0.0071), and thus no difference in the “acute” period between unpublished 4-c ube arrays based on their spacing (p=0.6264). This was the only significant ch ange on any of the unpublished array treatments. Within “Acute” The effect of publication on legal gag was most pronounced for arrays with larger reef patches (Figure 5). Th e number of legal gag on publis hed 16-cube arrays, however, was not significantly different than the numbe r of legal gag on pub lished 4-cube arrays (25 m p=0.5977; 225 m p=0.2462) or unpublished 4-cube arrays (25 m p=.0004 [greater abundance on four-cube arrays]; 225 m p=0.2380) Unpublished arrays maintained the size-dependent difference of more legal ga g on 16-cube than 4-cube arrays (25 m p=0.0005; 225 m p<0.0001). In the “acute” period a pattern emerged of more legal gag on unpublished 4-cube arrays relative to published 4-cube arrays for both spacing treatments (25 m p=0.0044; 225 m p=0.0249). More widely spaced arrays were hypothesized to be more difficult to fish and although there were more legal gag on published 16-cube arrays at the 225 m sp acing, the difference was not significant (p=0.0737).

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18 Transition from “Acute” to “Chronic” Following the initial impacts of publication observed in the “acute” period, none of the published arrays experienced significant changes (Figur es 3 and 4). On unpublished arrays, decreases indicative of discovery by anglers were observed. Although 4-cube, 25meter arrays did not change (p=0.2764), 4-c ube arrays at the 225meter spacing declined significantly (p=0.0483) (Figur e 4). Sixteen-cube arrays experienced a significant reduction in legal gag between the “acu te” and “chronic” periods at both spacing treatments (25m p=0.0010; 225m p<0.0001) (Figure 3). Within “Chronic” Despite the decrease on unpublished 16-cube, 25 m arrays, these arrays still held significantly more legal gag in the “chronic” period than did the published 16 cube, 25 m arrays (p=0.0003) (Figure 6). Reductions on unpublished arrays lead to there being no difference in legal gag abundances between 16-cube, 225 m arrays and their published counterparts (p=0.0872). Sixt een-cube arrays, both published and unpublished, did not show any difference by spacing (pub, p=0.1246; unpub, p=0.4132). Four-cube arrays showed a different pa ttern of gag abundanc e in the “chronic” period than the “acute.” Although there were still more legal gag on the unpublished 4cube, 25 m than the published 4 cube, 25 m arrays (p=0.0214), 4-cube, 225 m arrays showed no difference between published a nd unpublished treatments (p=0.7808) (Figure 6). As with the 16-cube a rrays, this was the result of a significant decrease on the unpublished arrays. Within publication treatm ents, spacing was not significant on 4-cube arrays (published p=0.45 19; unpublished p=0.0872) In the “chronic” period, patch size was no longer significant for any treatment. Effects of publication con tinued to be significant for 25 m arrays (4-cube p=0.0214; 16-

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19 cube p=0.0003), however, 225 m arrays no longe r showed any differences by publication (4-cube p=0.7808; 16-cube p=0.1812) Sub-Legal Gag There was a significant main effect of time period (p<0.0001) for sub-legal gag (Table 4). The three-way interaction between publication, patch size, and patch spacing was also significant (p=0.0513) (Table 4) give n the low replication and thus low expected power of this test. Mean square error was examined between treatment levels and determined not to be significantly different between levels of any treatment. Residual analysis indicated good model fit. The si gnificant model was run using untransformed data in order to generate leas t square means and error estimates for use in figures to better convey the results. The significant main effect of time period was manifested as a trend of decreasing abundance of sub-legal gag. Although the decrea se was not significant from the “pre” to the “acute” period (p=0.5617), it was significa nt from “acute” to “chronic” (p=0.0001). The significant effect of publication in the three-way interaction was only on 16cube, 25 m arrays. There were more sub-legal gag on the unpublished than published arrays (p=0.0151) (Figure 7). In most cases, there were more sub-lega l gag on 16-cube arrays than on 4-cube arrays. This held true for unpublished arrays (25 m p=0.0101; 225 m p=0.0017) as well as published 225 m arrays (p=0.0003), but not for published 25 m arrays (p=0.6966). Patch spacing had the most involved in teraction determin ing sub-legal gag abundance (Figure 8). There was a significant interaction with public ation as spacing had no significant effect on unpublished arrays (4-cube p=0.3868; 16-cube p=0.5679). Patch spacing and patch size interacted to aff ect patterns of sub-legal gag abundance on

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20 published arrays. There were more sub-lega l gag on published 16-cube arrays at the 225 m spacing than the 25 m spacing (p=0.0125). The opposite was true for the published 4cube arrays with more sub-legal gag on 25 m arrays than 225 m arrays (p=0.0188).

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21 Table 1. Type 3 tests of fixed effects for legal gag Covariance Parameters SubjectEstimateStd. Err.Z valuePr Z Reef 1.1787 0.6847 1.72 0.0462 Year (Period) Reef 2.3078 0.3555 6.49 <0.0001 Four-way interaction Num DF Den DF F-value Pr>F Pd*Fishing*Size*Dist 2 85.3 5.08 0.0083 Three-way interactions Num DF Den DF F-value Pr>F Pd*Fishing*Size 2 85.3 15.85 <0.0001 Pd*Fishing*Dist 2 85.3 4.01 0.0217 Pd*Size*Dist 2 85.3 2.72 0.0716 Fishing*Size*Dist 1 10.5 1.59 0.2344 Two-way interactions Num DF Den DF F-value Pr>F Pd*Fishing 2 85.3 27.51 <0.0001 Pd*Size 2 85.3 36.64 <0.0001 Pd*Dist 2 85.3 6.21 0.0030 Fishing*Size 1 10.5 3.22 0.1014 Fishing*Dist 1 10.5 0.60 0.4549 Size*Dist 1 10.5 4.39 0.0613 Main Effects Num DF Den DF F-value Pr>F Period 2 85.3 39.43 <0.0001 Fishing 1 10.5 48.20 <0.0001 Size 1 10.5 43.84 <0.0001 Distance 1 10.5 4.19 0.0664

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22 Table 2. Type 3 tests of fixed effects for sub-legal gag. Covariance Parameters SubjectEstimateStd. Err.Z ValuePr Z Reef 1.0481 0.7444 1.41 0.0795 Year (Period) Reef 3.6065 0.5661 6.37 <0.0001 Four-way interaction Num DF Den DF F-value Pr>F Pd*Fishing*Size*Dist 2 83.9 1.53 0.2222 Three-way interactions Num DF Den DF F-value Pr>F Pd*Fishing*Size 2 83.9 2.75 0.0695 Pd*Fishing*Dist 2 83.9 1.25 0.2928 Pd*Size*Dist 2 83.9 1.24 0.2937 Fishing*Size*Dist 1 10.5 4.83 0.0513 Two-way interactions Num DF Den DF F-value Pr>F Pd*Fishing 2 83.9 0.50 0.6088 Pd*Size 2 83.9 2.88 0.0615 Pd*Dist 2 83.9 0.24 0.7852 Fishing*Size 1 10.5 1.34 0.2719 Fishing*Dist 1 10.5 0.01 0.9252 Size*Dist 1 10.5 13.23 0.0042 Main Effects Num DF Den DF F-value Pr>F Period 2 83.9 12.44 <0.0001 Fishing 1 10.5 4.15 0.0675 Size 1 10.5 38.63 <0.0001 Distance 1 10.5 0.02 0.8831

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23 0 50 100 150 200 250 25225 Distance Between Patches (m)Legal Gag (per array) 4-cube 16-cube Figure 2. Pre-publication distribut ion of legal gag grouper on the SRRS. Data are drawn from not-to-be-published arrays due to the influence of pre-publication perturbations on to-be-published arrays. 0 50 100 150 200 250 PreAcuteChr Time PeriodLegal Gag (per array) Pub, 25m Pub, 225m Unpub, 25m Unpub, 225m Figure 3. Chronology of impacts to legal gag on 16-cube arrays of the SRRS by array architecture and publication status.

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24 0 10 20 30 40 50 60 70 80 90 PreAcuteChr Time PeriodLegal Gag (per array) Pub, 25m Pub, 225m Unpub, 25m Unpub, 225m Figure 4. Chronology of impacts to legal gag on four-cube arrays of the SRRS by array architecture and publication status. 0 50 100 150 200 250 4x25m4x225m16x25m16x225m Array ArchitectureLegal Gag (per array) Published Unpublished Figure 5. Abundance of legal gag per a rray within the “acute” period by array architecture and publication status.

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25 0 10 20 30 40 50 60 70 80 90 100 4x25m4x225m16x25m16x225m Array ArchitectureLegal Gag (per array) Published Unpublished Figure 6. Abundance of legal gag per array within the “chronic” period by array architecture and publication status. 0 50 100 150 200 250 4x25m4x225m16x25m16x225m Array ArchitectureSub-legal Gag (per array) Published Unpublished Figure 7. Abundance of sub-legal gag per ar ray, by array architecture and publication status, averaged across all time periods.

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26 A. Published Arrays0 50 100 150 200 250 416 Patch SizeSub-Legal Gag (per array) 25m 225m B. Unpublished arrays0 50 100 150 200 250 416 Patch SizeSub-Legal Gag (per array) 25m 225m Figure 8. Abundance of sub-legal gag per ar ray, by array architecture on (A) published and (B) unpublished arrays.

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27 CHAPTER 4 DISCUSSION The SRRS was designed to examine how sp atial components of habitat structure affect gag abundance. The subsequent publi cation of several array locations introduced directed fishing effort as an additional factor. Although no da ta were collected regarding fishing effort or angler behavior, differences between published and unpublished treatments are assumed to be due to directed fishing. Further, inferences are possible regarding angler behavior based on observed gag abundances on the SRRS. In a survey of recreational anglers in Dade County, FL, over 28% used artif icial reef sites, motivated by expectations of high catch rates (Milon, 1989 ). Fishing effort usually is positively related with fish abundance that “represent s a cumulative statistical summation of the effects of individual fisher choices” (Walters and Martell, 2004, p.205). For recreational anglers this leads to a rou ghly linear relationship between fish abundance and angling effort (Walters and Martell, 2004). On the SRRS this relationship is complicated by the rapid depletion of localized standing stocks of legal gag. The reduction in abundance lowers the benefit to anglers of selecting par ticular arrays and offers feedback to their decision-making process, but must have a la g as new experiences are likely slow to modify initial impressions and expectations. This experiment effectively demonstrated th e ability of anglers to remove the vast majority of legally harvestable fish from pub lished artificial reefs over the course of only a few years. Once published, size of reef patches had no impact on abundance of legal gag, indicating both large and small patches were fished down to a similar level. Over

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28 the six to eight years follow ing publication and the initial rapid reductions in legal gag, effort was apparently redirected to lo cating unpublished reef arrays. Changes on unpublished reef arrays can likel y be attributed to discovery by anglers as they were proportional to predicted impacts based on architecture. Large and widely-spaced patches (those most prone to discovery) expe rienced declines in abundance, while reef arrays composed of small closely-spaced pa tches did not change. Patterns in sub-legal gag abundance are driven by significant dec lines on the most heavily fished arrays (published, 16-cube, 25 m spaced). Several studies have reported higher abundances of fish on larger habitat patches or patches providing more refuge (de Bo er 1978; Roberts and Ormond 1987; Hixon and Beets, 1989; Rountree, 1989; Kuwamura et. al. 1994, Eggleston et. al 1998; Abelson and Shlesinger 2002). The initial conditions obs erved on the SRRS with regard to array architecture are thus not su rprising. Studies of gag home range on the SRRS (Kiel 2004) and residency (Lindberg et. al. in press) have indicated th at reef patches spread 25 m apart are collectively used as a single home -site whereas 225 m spaced patches are used independently. The fact that fishing had both an immedi ate and significant impact on the largest aggregations of gag is not surprising. Reduc tions in catch assumed to be reflective of similar reductions in abunda nce were observed by Grandc ourt (2003) in monitoring the exploitation of a virgin stock of crimson jobfish, Pristipomoides filamentous a shelf-edge hook and line fishery. There are also numerous examples in the literature of comparisons between both recreationally and commercially fished and un-fi shed areas in which there are more fish and larger fish in protec ted areas than unprotected ones (Roberts, 1994;

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29 Jennings and Polunin, 1996; Wantiez et. al ., 1997, Guidetti et. al., 2005, Kamukuru et. al., 2005) as well as declines over time of exploited stocks (Haedrich and Barnes, 1997; Fogarty and Murawski 1998; McClanahan and Mangi, 2001; Albaret and Lae 2003; Laurans et. al., 2004). Solonsky (1985) demonstr ated the significant impact of fishing on artificial reefs in Monterey Bay, CA. A singl e marked reef was constructed amidst other unmarked reefs. Observed abundance of le gal-sized rockfish on the marked reef was reduced after three years of fishing effort re lative to the unmarked reefs. Furthermore, tagged fish were observed to move from unmark ed reefs to the marked reef, but not vice versa, indicating the potential ‘si nk’ quality of a fished artifi cial reef. Similar movements of fish (from natural to artificial reefs, but not back) were observed in Puerto Rico (Fast and Pagan, 1974) On the SRRS we had the unique oppor tunity to examine the manner in which variable spatial qualities of reefs inte ract with fishing effort to determine the abundance of a targeted species. Although 25 and 225 m published 16-cube arra ys experienced significant declines in abundance of legal gag following publicati on, the predicted refuge effect of more widely spaced arrays was only marginally si gnificant in the “acute” period. There are several potential mechanisms for such a refuge effect. Since gag treat 25 m arrays as a single home-site, fishing effort, even when focused on a single patch, is effectively fishing the entire array due to the movement of gag among patches. There is also a significant margin of error for non-anchored fi shing techniques (drift -fishing or trolling) on 25 m arrays. Should the boat’s course not take it over the inte nded patch, it is far more likely to encounter gag on another patc h, or between patches. Furthermore, 25 m spaced arrays are likely to be more appea ling to spear-fishermen who can easily swim

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30 between patches in search of legal gag. All of these factors likely contribute to higher attractiveness to anglers of 25 m arrays relative to 225 m arrays. An additional consideration is that 225 m spaced patches may recruit more gag as a result of their larger footprint, simply by an increased chance of encounter by gag, however, immigration rates and residence times under fished conditions, relative to removal rates by anglers are unknown. While the publication of array locations le d to a rapid depletion of legal gag on 16cube patches, 4-cube patches did not change significantly with publication. Both their smaller size and lower abundances of gag make them more difficult to locate and fish effectively. Furthermore, the four cube arrays were likely less attr active to anglers based on the common conception that smaller reef s hold fewer fish. Although there was no significant change on the published four-cube arrays between the “pre” and “acute” periods, there was a significan t effect of publication within the “acute” period (more legal gag on unpublished arrays). Keeping in mind th at there were randomization restrictions in assignment of publication treatments becau se of earlier perturba tions, the effect of publication on four-cube arrays may have b een to maintain low abundances on these arrays, rather than to depress them below their pre-publication levels. The immediacy of the decrease in gag a bundances following publication is further emphasized by the fact that none of the published treatments demonstrated any significant further decreases between th e “acute” and “chronic” periods. A new equilibrium abundance appears to have been reached in which legally harvestable fish were maintained at low levels by fishing activi ties. The increase in the minimum size of recreationally harvestable gag between th e “acute” and “chronic” periods had the

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31 potential to further decrease abundances of legal gag as those between 508 and 550 mm would be considered sub-legal in the “chroni c” period. There was, however, a significant decrease of sub-legal gag betw een these periods, indicating that this was a minimal effect in relation to the other pro cesses affecting abundances of legal and sub-legal gag on the SRRS. Because the SRRS represents only a way-point in the spatially st age-structured life history of gag, there is a constant immigra tion to and emigration from the reefs. In studies done prior to introduc ing the publication treatment, mean residence time for an individual gag was 9.8 months (Lindberg et. al in press). It is assumed that newly arriving gag make a decision as to whether to stay or not based on current conditions on the patch. Although density-dependent habita t selection has been confirmed for gag (Lindberg et. al., in press), th e exact influence of the standi ng stock of gag on an array in the decision making process of newly arrivi ng gag is unknown. On arrays depleted by fishing, it seems reasonable that newly arri ved legal-sized gag would find themselves among the dominant fish present and be more likel y to stay on the reef than if there was a full compliment of un-fished legal gag presen t. In this manner there may be a higher percentage of newly arrived gag deciding to stay on published patches, thus making themselves vulnerable to fishing, than on unpublished patches or patches prior to publication. Fully understanding the rate at wh ich gag arrive, and the proportion of those taking up residence, as well as criteria important in maki ng such a decision, would be a big step forward in understanding the impli cations of fishing on habitat selection and habitat-specific mortality risk.

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32 The tendency of gag to aggregate in speci fic habitats known to recreational anglers fits the definition of an ‘ ecological trap’ (Schlaepfer et al., 2002). The concept of ecological traps has most widely been applie d to terrestrial envi ronments. Ecological traps result when an organism makes a mal-adaptive habitat selection, due most frequently to an anthropogenic change or ma nipulation of the environment, based on cues that over evolutionary time were correlated with improved fitne ss. In the marine environment, the tendency of many game-fish species to associate with structure can be interpreted as an ecological trap. Once disc overed by anglers, high quality habitat (both artificial and natural) will continue to attract and aggreg ate both fish and the anglers targeting them. In the case of the SRRS, the artificial reef patches are high quality habitat (Lindberg et. al. in press) providing gag both refuge and a prey base. The outcome, however, is an aggregation accurately predictabl e in space, leading to the removal of the majority of legally harvestable gag. The decision to take up residence on published patches of the SRRS seems to meet the criter ia of an ecological trap (Schlaepfer et. al. 2002), but could only be conclusively defined as such with complete knowledge of the overall reproductive success of gag taking up residence on the SRRS relative to those inhabiting natural hard-bottom habitats. One of the most telling results is the lack of any significant difference between size treatments of both published and unpublished ar rays during the “chronic” period. While other factors such as catch-ability of legal gag and by-catch of under-sized gag factor into the benefit to anglers of fishing an array, th e primary focus is assumed to be harvest of legal gag, and each size of reef provides simila r potential harvest at its new equilibrium abundance. This indicates that the additiona l shelter on 16-cube patches does not provide

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33 gag any greater protection from fishing rela tive to the four-cube arrays. Also, when constructing reefs for the benefit of the gag, the additional investment in construction materials is not justified by its potential to house more legal gag under conditions where recreational fishing will occur. The predictable impacts of fishing on the SRRS extend beyond the published arrays. Ultimately the unpublished arrays of the SRRS are all predicted to become discovered. Thus the rate of progression from their un-fished state in the pre-publication period and “acute” period to their moderately -fished state in the “ch ronic” period is an indication of their combined ease of discovery and subsequent value as fishing sites. Between the “acute” and “chronic” periods, unpu blished 16-cube arrays, in both spacing treatments, experienced significant declines in legal gag. This is believed to be due to increased fishing effort, most likely from dir ected efforts in respons e to declining catches on published arrays, but also possibly due to simple chance, to locate sites that were known to exist. Sixteen-cube arrays would be the most susceptible to discovery as they have a larger footprint than four-cube arrays, and larger aggregations of gag, thus providing the largest targets fo r searching anglers. Of th e four-cube arrays, only the 225meter spaced treatments showed significant e ffects of discovery. The probability of a searching angler encountering an array is higher on more-widely and systematically spaced arrays where there is likely less ove rlap of the areas used by gag on different patches. As the types of array architectures within the SRRS were publicly known, discovery of one patch within an array should be interpreted as discove ry of the array as a whole.

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34 Impacts of directed fishing extended beyond the removal of legally-harvestable gag to the sub-legal gag. All comparisons i nvolving published, 16-cube, 25-meter arrays demonstrated the impacts of fishing pressure on sub-legal gag. This treatment apparently received the highest level of fi shing effort and thus was the fi rst to demonstrate effects of that angling pressure trickli ng down to the sub-legal gag. First, there were more sublegal gag on unpublished arrays of this arch itecture than published arrays. Second, there was no difference between this treatment a nd 4-cube, published arrays at the 25-meter spacing. In all other treatment combinations 16-cube arrays held more sub-legal gag than 4-cube arrays as woul d be expected by the amount of shelter provided. Finally, published, 25-meter spaced, 16-cube arrays had fewer sub-legal gag than the more widely-spaced, published, 16-cube arrays, a pattern that was not observed among the unpublished arrays. Hooking mortality, illegal harvest, and induced emigration are all potential mechanisms by which sub-legal gag may be affected. No data were collected to determine the relative importance of these mechanisms. Catch and release associated mortality from recreational anglers has been measured to be as high as 20 % from headboat fisheries (R. Dixon, NMFS, persona l communication). These gag, however, were caught from a minimum de pth of 25 m where there is a greater effect of swim bladder expansion than occurs on the SRRS in 13 m of water, and they were not followed beyond release. Both depth-related effects as well as hooking effects contribute to release mortality. In a study of depth-relate d capture-release mortality on gag, where gill or gut-hooked fish were not included, no ga g caught from 20 m of water showed any adverse depth-related effects of being caught (C. Koenig, FSU, unpublished data). Hooking mortality on another serranid, Epinephelus quoyanus in shallow waters (<2m)

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35 of the Great Barrier Reef, wher e depth related effects were not a factor, was found to be highest at 5.1% when bait-fish ing with single hooks (Diggles and Ernst, 1997). Actual catch and release mortality on the SRRS is lik ely close to this figur e, as bottom-fishing with natural bait is a very co mmon technique. It is likely that many legal gag are hooked several times before being landed and th at sub-legal gag are both hooked and landed without being harvested from the system Beyond hooking mortality, the role these experiences play in modifying behavior a nd possibly residence times of surviving gag may be of importance. The main effect of time period on sub-le gal gag abundance manifested itself in a decreasing trend over time. The only significan t change, however, was from the “acute” period to the “chronic” period. The lack of an interaction with publication makes interpretation somewhat troublesome. It is possible that there were simply several years of smaller year-classes of gag colonizing the SRRS. The continued directed angling efforts both on published and unpublished arra ys following the “acute” period, however, certainly contributed to the decline. This study has revealed an interaction of spa tial qualities of ha bitat and angling pressure, mediated by detailed information of those habitat qualities, in determining local abundances of a targeted reef-d ependent species. The relativ e benefit to gag that occupy small patches of artificial habitat are clear. Widely-spaced patches within an array increase the probability of a single patch be ing discovered. Discovery of a single patch, in this case, should lead to di scovery of the array as a whol e as anglers are familiar with the layout of patches in the SRRS. While the end results have been demonstrated there is still uncertainty in the precise mechanisms, and their relative importance, combining to

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36 produce the observed patterns. Identifying a nd quantifying these mechanisms would be important for applying the results of this study to management decisions for gag, other fish and other systems. Additional informa tion regarding the usage and opinions of the SRRS in the angling community could validate several of the assumptions and inferences made herein as well as increase the applicabil ity of conclusions drawn in this study. The publication of detailed geographic information in this case allowed anglers to select or disregard fishing sites according to thei r expectations of su ccess based on habitat architecture. The continued development of such detailed information regarding natural habitats will enhance efficiencies in the exploitation of natural resources.

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37 REFERENCES Ableson, A. and Shlesinger, Y. (2002). Compar ison of the development of coral and fish communities on rock-aggregated artificial reef in Eilat, Red Sea. ICES Journal of Marine Science. 59 S122-S126. Albaret, J. and Lae, R. (2003). Impact of fi shing on fish assemblages in tropical lagoons: the example of the Ebrie lagoon, West Africa. Aquatic Living Resources. 16 1-9. Andersen, H., McGaughey, R.J., and Reutebuc h, S.E. (2005). Estimating forest canopy fuel parameters using LIDAR data. Remote Sensing the Environment. 94 441-449. Berkeley, S.A., Hixon, M.A., Larson, R.J. and Love, M.S. (2004a). Fisheries sustainability via protection of age stru cture and spatial distribution of fish populations. Fisheries. 29 23-32. Berkeley, S.A., Chapman, C. and Sogard, S.M. (2004b). Maternal age as a determinant of larval growth and survival in a marine fish, Sebastes melanops Ecology. 85 12581264. Bianchi, G., Gislason, H., Graham, K., Hill, L., Jin, X., Koranteng, K., ManickchandHeileman, S., Paya, I., Sainsbury, K., Sa nchez, F. and Zwanenburg, K. (2000). Impact of fishing on size composition and diversity of demersal fish communities. ICES Journal of Marine Science. 57 558-571. Birkeland, C. and Dayton, P.K. (2005). The impo rtance in fishery management of leaving the big ones. Trends in Ecology and Evolution. 20 356-358. Bohnsack, J.A., Harper, D.E., McClellan, D.B. and Hulsbeck, M. (1994). Effects of reef size on colonization and assemblage struct ure of fishes at artificial reefs off southeastern Florida, U.S.A. Bulletin of Marine Science. 55 796-823. Bremner, J., Frid, C.L.J. and Rogers, S.I. (2003). Assessing marine ecosystem health: The long-term effects of fishing on functi onal biodiversity in North Sea benthos. Aquatic Ecosystem Health and Management. 6 131-137. Brown, E.D., Churnside, J.H., Collins, R.L., Veenstra, T., Wilson, J.J. and Abnett, K. (2002). Remote sensing of capelin and other biological features in the North Pacific using lidar and video technology. ICES Journal of Marine Science. 59 1-11. Brule, T., Deniel, C., Colas-Marrufo, T. and Renan, X. (2003). Reproductive biology of gag in the southern Gulf of Mexico. Journal of Fish Biology. 63 1505-1520.

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38 Bullock, L.H. and Smith, G.B. (1991). Seaba sses (Pisces: Serranid ae). Memoirs of the Hourglass Cruises. Marine Research La boratory, Florida Depa rtment of Marine Resources, St. Petersburg, FL. 8 1-205. Carr, M.H., Anderson, T.W., and Hixon, M.A. (2002). Biodiversity, population regulation, and the stability of coral-reef fish communities. Proc. Nat. Acad. Sci. 99 11241-11245. Charbonnel, E., Serre, C., Ruitton, S., Harmelin, J. and Jensen, A. (2002). Effects of increased habitat complexity on fish assemblages associated with artificial reef units (French Mediterranean coast). ICES Journal of Marine Science. 59 S208S213. Coleman, F.C., Figueira, W.F., Ueland, J.S. and Crowder, L.B. (2004). The impact of United States recreational fisheries on marine fish populations. Science. 305 19581960. Coleman, F.C., Koenig, C.C. and Chap man, R. (2002). Review of Kenchington Document “Management of the Gulf of Mexico Gag Grouper Fisheries: A Reconsideration”. Tallahassee, Department of Biological Scie nce, Florida State University: 20p. Coleman, F.C., Koenig, C.C. and Collins, L. A. (1996). Reproductive styles of shallowwater groupers (Pisces: Serranidae) in the eastern Gulf of Mexico and the consequences of fishing spawning aggreg ations. Environmenta l Biology of Fishes. 47 129-141. Coll, J., Moranta, J., Renones, O., Garcia-R ubies, A. and Moreno, I. (1998). Influence of substrate and deployment time on fish a ssemblages on an artificial reef at Formentera Island (Balearic Islands, we stern Mediterranean ). Hydrobiologia. 385 139-152. Collins, L.A., Johnson, A.G., Koenig, C.C. and Baker, M.S. Jr. (1998). Reproductive patterns, sex ratio, and fecundity in gag, Mycteroperca, microlepis (Serranidae), a protogynous grouper from the northeastern Gulf of Mexico. Fishery Bulletin. 96 415-427. Conover, D.O. and Munch, S.B. (2002). Sustai ning fisheries yields over evolutionary time scales. Science. 297 94-96. De Boer, B.A. (1978). Factors influenci ng the distribution of the damselfish Chromis cyanea (Poey), Pomacentridae, on a reef at Curacao, Netherlands Antilles. Bulletin of Marine Science. 28 550-565. Diggles, B.K. and Ernst, I. (1997). Hooking mo rtality of two species of shallow-water reef fish caught by recreational angling me thods. Marine and Freshwater Research. 48 479-483.

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39 Ditton, R.B. and Graefe, A.R. (1978). Recreatio nal fishing use of ar tificial reefs on the Texas Gulf Coast. Texas Agricultural E xperiment Station, Texas A&M University, College Station. 155pp. Doherty, P.J. and Sale, P.F. (1985). Predation on juvenile coral reef fishes: an exclusion experiment. Coral Reefs. 4 225-234. Eggleston, D.B., Etherington, L.L. and Elis, W.E. (1998). Organism response to habitat patchiness: species and ha bitat-dependent recruitment of decapod crustaceans. Journal of Experimental Marine Biology and Ecology. 223 111-132. Eklund, A.M. (1997). The importance of post-se ttlement predation and reef resources limitation on the structure of reef fish assemblages. Proccedings of the 8th International Coral Reef Symposium. 2 1139-1142. Fast, D.E. and Pagan F.A. (1974). Comparative observations of an ar tificial tire reef and natural patch reefs off southwestern Puerto Rico. Pages 49-50 in L. Colunga and R. Stone, eds. Proceedings: artificial reef conference. Texas A&M University, TAMU-SG-74-103. Fogarty, M.J. and Murawski, S.A. (1998). Larg e-scale disturbance a nd the structure of marine systems: fishery impacts on Geor ges Bank. Ecological Applications. S6S22. Frazer, T.K. and Lindberg W.J. (1994). Refuge spacing similarly affects reef-associated species from 3 phyla. Bulletin on Marine Science. 55 388-400. Gilmore, R.G. and Jones, R.S. (1992). Color variation and associat ed behavior in the epinepheline groupers, Mycteroperca microlepis (Goode and Bean) and M. phalanx Jordan and Swain. Bulletin of Marine Science. 51 83-103. Grandcourt, E.M. (2003). The effect of intens ive line fishing on the virgin biomass of a tropical deepwater snapper, the crimson jobfish ( Pristopomoides filamentosus ). Fisheries Bulletin. 101 305-311. Gratwicke, B. and Speight, M.R. (2005). E ffects of habitat complexity on Caribbean marine fish assemblages. Marine Ecology Progress Series. 292 301-310. Guidetti, P., Verginella, L., Viva, C., Odoric o, R. and Boero, F. (2005). Protection effects on fish assemblages and comparison of tw o visual-census techniques in shallow artificial rocky habitats in the northern Ad riatic Sea. Journal of the Marine Biology Association of the U.K. 85 247-255. Haedrich, R.L. and Barnes, S.M. (1997). Cha nges over time of the si ze structure in an exploited shelf fish comm unity. Fisheries Research. 31 229-239.

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40 Harris, P.J. and Collins, M.R. (2000). Age, growth and maturity of gag, Mycteroperca microlepis from the southeastern United States during 1994-1995. Bulletin of Marine Science. 66 105-117 Hart, M. (2002). Habitat-mediated direct and indirect effects among th ree Serranid fishes. Master’s Thesis. University of Florida, Gainesville, Florida. Hauser, L., Adcock, G.J., Smith, P.J., Ramirez, J.H.B., and Carvalho, G.R. (2002). Loss of microsatellite diversit y and low effective population size in an overexploited population of New Zealand snapper ( Pagrus auratus ). Proc. Natl. Acad. Sci. U.S.A. 99 11742-11747. Herrera, R., Espino, F., Garrido, M., Haroun, R.J. (2002). Observations on fish colonization and predation on two artificia l reefs in the Canary Islands. ICES Journal of Marine Science. 59 S69-S73. Hixon, M.A. and Beets, J.P. (1989). Shelte r characteristics and Caribbean fish assemblages: experiments with artificial reefs. Bulletin of Marine Science. 44 666680. Hood, P.B. and Schleider, R.A. (1992). Age, growth, and reproduction of gag, Mycteroperca microlepis (Pisces: Serranidae), in th e eastern Gulf of Mexico. Bulletin of Marine Science. 51 337-352. Jennings, S. and Polunin, N.V.C. (1996). Effects of fishing effort and catch rate upon the structure and biomass of Fijian reef fish communities. Journal of Applied Ecology. 33 400-412. Kamukuru, A.T., Hecht, T. and Mgaya, Y.D. (2005). Effects of exploitation on age, growth and mortality of the blackspot sanpper, Lutjanus fulviflamma at Mafia Island, Tanzania. Fisheries Management and Ecology. 12 45-55. Keener, P., Johnson, G.D., Stender, B.W., Brothers, E.B. and Beatty, H.R. (1988). Ingress of postlarval gag, Mycteroperca microlepis (Pisces: Serranidae), through a South Carolina barrier island inle t. Bulletin of Marine Science. 42 376-396. Kenchington, T.J. (1999). Management of the Gulf of Mexico gag grouper fisheries: A reconsideration (revised version). Gadus Associates report prepared for the Southeastern Fisheries Association Inc ., Musquodoboit Harbor, Nova Scotia: 47pp. Kiel, B.L. (2004). Homing and spatial use of gag grouper, Mycteroperca microlepis Masters Thesis. University of Florida, Gainesville, Florida. Kinkade, K. (2003). Sensors and lasers map ebb a nd flow of ocean life. Laser Focus World. 39 91-96.

PAGE 49

41 Koenig, C.C., Chapman, R.W., Collins, M.R., Harris, P., McGovern, J., Sedberry, G.R., Wyanski, D.M., and A.G. Johnson. (1999). The effects of shelf-edge fishing on the demographics of the gag, Mycteroperca microlepis population of the southeastern United States. Tallahassee, FL, Department of Biological Scie nce, Florida State University. Kostylev, V.E., Courtney, R.C., Robert, G. and Todd, B.J. (2003). Stock evaluation of giant scallop ( Placopecten magellanicus ) using high-resolution acoustics for seabed mapping. Fisheries Research. 60 479-492. Kuwamura, T., Yogo, Y. and Nakashima, Y. (1994). Population-dynamics of goby Paragobiodon Echinocephalus and host cora l Stylophora-pistillata. Marine Ecology Progress Series. 103 17-23. Laurans, M., Gascuel, D., Chassot, E. a nd Thiam, D. (2004). Changes in the trophic structure of fish demersal communities in West Africa in the last three decades. Aquatic Living Resources. 17 163-173. Lee, S.H. and Kim, K. (2004). Side-scan sonar characteristics and manganese nodule abundance in the Clarion-Clippe rton Fracture Zones, NE e quatorial Pacific. Marine Georesources and Geotechnology. 22 103-114. Leimgruber, P., Christen, C.A., Laborderie, A. (2005). The impact of Landsat satellite monitoring on conservation biology. Envir onmental Monitoring and Assessment. 106 81-101. Ley, J.A., Halliday, I.A., Tobin, A.J., Garrett R.N. and Gribble N.A. (2002). Ecosystem effects of fishing closures in mangrove estuaries of tropical Australia. Marine Ecology Progress Series. 245 223-238. Lindberg, W.J. and Loftin, J.L. (1998) Effects of artifical reef charac teristics and fishing mortality on gag ( Mycteroperca microlepis ) productivity and r eef fish community structure. Final Project Report, Florida Marine Resources Grants Number MR-073. 47pp. Lindberg, W.J., Frazer, T.K., Portier, K.P., Vose F., Loftin, J, Murie, D.J., Mason, D.M., Nagy, B., and Hart, M.K. Density-dependent habitat selection and performance by a large mobile reef fish. Ecol ogical Applications. In Press. Mack, P.E. (1990). Viewing the Earth: The soci al construction of the Landsat Satellite System. MIT Press, Cambridge, USA. McClanahan, T.R. and Mangi, S. (2001). The effect of a closed area and beach seine exclusion on coral reef fish catches. Fisherie s Management and Ecology. 8 107121.

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42 McGlennon, D. and Branden, K.L. (1994). Comp arison of catch and recreational anglers fishing on artificial reefs and natural seabed in Gulf St. Vincent, South Australia. Bulletin of Marine Science. 55 510-523. McErlean, A.J. (1963). A study of th e age and growth of the gag, M ycteroperca microlepis Goode and Bean (Pisces: Serranid ae) on the west coast of Florida. Florida Board of Conservation Mari ne Laboratory, Technical Series. 41 29pp. Milon, J.A. (1989). Artifi cial marine habitat characteristic s and participation behavior by sport anglers and divers. Bulletin of Marine Science. 44 853-862. Morton, R.A., Miller, T. and Moore, L. (2005) Historical shoreline changes along the US Gulf of Mexico: A summary of recent shoreline comparisons and analyses. 21 704-709. Pamo, E.T. (2004). Community production prac tices and desertifica tion in the SaheloSudanian region of Cameroon at the tu rn of the millennium. Environmental Monitoring and Assessment. 99 197-210. Pickrill, R.A., Todd, B.J. (2003). The multiple roles of acoustic mapping in integrated ocean management, Canadian Atlantic continental margin. Ocean and Coastal Management. 46 601-614. Roberts, C.M. (1994). Rapid build-up of fish biomass in a Caribbean marine reserve. Conservation Biology. 9 815-826. Roberts, C.M., Bohnsack, J.A., Gell, F., Hawkins, J.P. and Goodridge, R. (2001). Effects of marine reserves on adjacent fisheries. Science. 294 1920-1923. Roberts, C.M. and Ormond, R.F.G. (1987). Ha bitat complexity and coral reef fish diversity and abundance on Red Sea fri nging reefs. Marine Ecology Progress Series. 41 1-8. Ross, S.W. and Moser, M.L. (1995) Life history of juvenile gag, Mycteroperca microlepis, in North Carolina estuaries. Bulletin of Marine Science. 56 222-237. Rountree, R.A. (1989). Association of fishes with fish aggregation devices: effects of structure size on fish abundance. Bulletin of Marine Scienec. 44 960-972. Schlaepfer, M.A., Rungs, M.C. and Sherma n P.W. (2002). Ecological and evolutionary traps. Trends in Ecology & Evolution. 17 474-480. Sherman, R.L., Gilliam, D.S. and Spieler, R.E. (2002). Artificial reef design: void space, complexity and attractants. ICES Journal of Marine Science. 59 S196-S200. Shulman, M.J. (1984). Resource limitation and recruitment patterns in a coral reef assemblage. Journal of Experimental Marine Biology. 74 85-109.

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43 Solonsky A.C. (1985). Fish colonization and the effect of fish ing activities on two artificial reefs in Monterey Bay, Cali fornia. Bulletin of Marine Science. 37 336347. Sweatman, H.P.A. (1985). The influence of adul ts of some coral reef fishes on larval recruitment. Ecological Monographs. 55 469-485. Szedlmayer, S.T. and Lee, J.D. (2004). Di et shifts of juvenile red snapper ( Lutjanus campechanus ) with changes in habitat a nd fish size. Fishery Bulletin. 102 366-375. Turner, S.C., Porch, C.E., Heinemann, D., Scott, G.P. and Ortiz, M. (2001). Status of gag in the Gulf of Mexico, Assessment 3.0. NMFS Southeast Fisheries Center, Miami Laboratory, Miami SFD 01/02 –134. 33p. Turpin, R.K. and Bortone, S.A. (2002). Preand post-hurricane assessment of artificial reefs: evidence for potential use as refugi a in a fishery management strategy. ICES Journal of Marine Science. 59 S74-S82. Verlaan, P.A. (1997). New seafloor ma pping technology and Article 76 of the 1982 United Nations Convention on the Law of the Sea. Marine Policy. 21 425-434. Walters, C.J. and Martell, S.J.D. (2004). Fisheries Ecology and Management. Princeton University Press, Princeton, New Jersey, USA. Wantiez, L., Thollot, P. and Kulbicki, M. ( 1997). Effects of marine reserves on coral reef fish communities from five islands in New Caledonia. Coral Reefs. 16 215-224. Weaver, D.C. (1996). Feeding ecology and eco morphology of three sea basses (Pisces: Serranidae) in the northeaste rn Gulf of Mexico. Thesis University of Florida, Gainesville, Florida. Williams, D.McB., and Sale, P.F. (1981). Spatial and temporal patterns of recruitment of juvenile coral reef fishes to coral hab itats within “One Tr ee Lagoon,” Great Barrier Reef. Marine Biology. 65 245-253. Wright, D.J. (1999). Getting to the bottom of it: Tools, techniques, and discoveries of deep ocean geography. Professional Geographer. 51 426-439.

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44 BIOGRAPHICAL SKETCH The author was born in Washi ngton, D.C. During his early years he was fascinated by the fish, frogs, turtles and insects that he caught and raised and watched in his neighborhood streams and ponds. As early as pre-school he was the tender of the class aquarium. His first exposure to the scien tific method came from Stanley Edwards, his science teacher from fourth through sixth gr ades. Mr. Edwards effectively conveyed his own passion for the sciences and natural world. During summer vacation following his s ophomore year of high school, he began volunteering for Dr. Marjorie Reaka-Kudla, a coral reef biologist at the University of Maryland. Being invited on a tw o-week research trip to the Florida Keys as a 16-yearold who was half way through high-school convi nced him he was in the right field. Involvement in her research continued through his high school years. He attended the University of California at Santa Barbara from wh ich he graduated in 1998 with a Bachelor of Science degree in aqua tic sciences. After gr aduation he returned to the University of Maryland, this tim e working with Dr. David Secor of the University’s Chesapeake Biological Laborat ory. Following three years as a faculty research assistant he decided to return to school in pursuit of a master degree. The opportunity to again work beneath the water dr ew him to the University of Florida where he studied under Dr. William J Lindberg.

PAGE 53

45 Following graduation he has accepted a positi on in Gainesville, FL, with Golder Associates, an environmental consulting firm.


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INFLUENCE OF HIGH-RESOLUTION SPATIAL INFORMATION ON RESOURCE
EXPLOITATION: AN EXAMPLE FROM ANGLER IMPACTS ON ARTIFICIAL
REEFS











By

STEPHEN J. LARSEN


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


2005

































Copyright 2005

by

Stephen J. Larsen















ACKNOWLEDGMENTS

I thank my advisor Dr. William J Lindberg for introducing me to the Gulf of

Mexico ecosystems and encouragement to see and think about the big picture. This

research and the completion of my graduate career would not have been possible without

his guidance, optimism, and perspective on the project at hand. I thank Dr. Debra Murie

for serving on my committee and for her guidance and input throughout my graduate

experience. I thank Dr. Tom Frazer for serving on my committee as well as providing

perspective on what the important things are and not to lose sight of them.

Enormous thanks go out to Dr. Ken Portier for his help with the statistical aspects

of this project. Thanks also to Dr. Mike Allen for statistical guidance and the

encouragement to complete the degree for there are bigger and better things following

graduation. Special thanks go to lab-mates Doug Marcinek, Mark Butler, and Brian

Nagy who collectively welcomed me into the Lindberg Lab, made my transition to

graduate school easy and provided a great sounding board for ideas, discussions, and

frustrations. Additional thanks go to graduate students Rick Kline, Mark Rogers, and

Paul Anderson for always being willing to give time even when they had none to give. In

fact every graduate student who passed through the carrels of the Fisheries and Aquatic

Sciences Department from August, 2001, through Fall, 2005, contributed to a great work

environment and community of friends that is regrettably so temporary in nature.
















TABLE OF CONTENTS



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

L IST O F T A B L E S ..................................................................... .....................

L IST O F FIG U R E S .... .............................. ....................... .......... ............... vi

ABSTRACT .............. ..................... .......... .............. vii

CHAPTER

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

2 M E TH O D S .................................................................9

Experim mental System .................. .............................. ....... ...............
Study Organism ....................................................................... ......... 10
S ou rces of D ata ............................................................................... 1 1
Suitability of D ata...................................................... 12
E xperim mental D design ........................ ................ .. ......... ....... 13
S statistic al A n aly se s .....................................................................................................13

3 R E S U L T S ........................................................................................................1 6

L egal G ag .....................................16
Pre-publication Time Period (Initial Conditions) .............................................16
Transition from "Pre" to "Acute" Time Periods .............................................17
W within "A cute" .................................. .......................... ..... ............ 17
Transition from "A cute" to "Chronic" ............ ................................ ...............18
W within "Chronic" .................. ................................... .... ........... .18
Sub-L egal G ag ................................................................ .. .... ......... 19

4 DISCUSSION .................. .................................... ........... .... .......... 27

REFERENCES ................... ......... .. ...... ... ..................37

B IO G R A PH IC A L SK E TCH ..................................................................... ..................44





iv
















LIST OF TABLES


Table page

1. Type 3 tests of fixed effects for legal gag ................................. .......... ...... ......... 21

2. Type 3 tests of fixed effects for sub-legal gag.....................................................22















LIST OF FIGURES


Figure page

1. Design of the Suwannee Regional Reef System ................................ ..................... 15

2. Pre-publication distribution of legal gag grouper on the SRRS. Data are drawn
from not-to-be-published arrays due to the influence of pre-publication
perturbations on to-be-published arrays. ........................................ ............... 23

3. Chronology of impacts to legal gag on 16-cube arrays of the SRRS by array
architecture and publication status. ............................................... ............... 23

4. Chronology of impacts to legal gag on four-cube arrays of the SRRS by array
architecture and publication status. ............................................... ............... 24

5. Abundance of legal gag per array within the "acute" period by array architecture
and publication status. .................................... ...............................24

6. Abundance of legal gag per array within the "chronic" period by array architecture
and publication status. .................................... ...............................25

7. Abundance of sub-legal gag per array, by array architecture and publication status,
averaged across all tim e periods........................................ ........................... 25

8. Abundance of sub-legal gag per array, by array architecture on (A) published and
(B ) unpublished arrays. ...................... .. ...... .............. ...................... .....26














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

INFLUENCE OF HIGH-RESOLUTION SPATIAL INFORMATION ON RESOURCE
EXPLOITATION: AN EXAMPLE FROM ANGLER IMPACTS ON ARTIFICIAL
REEFS

By

Stephen J. Larsen

December 2005

Chair: William J. Lindberg
Major Department: Fisheries and Aquatic Sciences

Exploitation of natural resources is dependent on knowing where to find those

resources. Increasingly specific and detailed information regarding the location and

relative value of many resources is being continually developed by rapidly advancing

technologies in remote sensing. It is generally assumed that such information allows

more efficient and directed exploitation of those resources. I evaluated impacts of the

public release of detailed geographic information regarding artificial reefs designed for

gag grouper (Mycteroperca microlepis). Reefs were constructed of concrete cubes

approximately 90 cm on a side. Size of reef patches (4-cube and 16-cube, small and large

respectively), and distances among patches (25 m and 225 m), were examined.

Approximately half of the reef locations were published to the angling community. Reefs

were monitored from two years prior to publication to two years-post publication and

again six to eight years post-publication.









Impacts on published reef arrays were highest on large, closely spaced reef arrays,

and least on small, widely spaced reef arrays. In contrast to pre-publication trends, large

reef patches, once published, no longer held more legal gag (>508 mm) than small

patches. Six to eight years after publication sub-legal gag (<508 mm) were reduced on

the largest, most closely spaced arrays, indicating that these reefs received the highest

fishing effort. Large unpublished reefs as well as small, widely spaced reefs showed

effects of discovery by anglers in the period six to eight years after other reefs in the

study system were made publicly known. The disclosure of locations of previously un-

targeted, high-quality habitat led to immediate exploitation of legal gag, with the

exception of apparent refuges of small habitat patches, which are inherently more

difficult to locate and to fish. Resource managers should take into account the improved

efficiency of exploitation made possible by the collection and dissemination of high-

resolution geographic habitat data.














CHAPTER 1
INTRODUCTION

Accurate and rapid collection of spatially explicit data regarding the natural

environment has been made possible over recent decades by the development of new

technologies. Advances in satellite imaging and sensing systems as well as sonic and

laser technologies are providing unprecedented detail and information. The utility of

high-resolution spatial data to both resource managers and user groups has been clear. It

has made possible the quantification of changes in land use and land cover to describe

processes such as deforestation and desertification (Pamo, 2004; Leimgruber et. al.,

2005) and shoreline changes (Morton et. al., 2005) with much greater accuracy than prior

techniques, provided for far more proficient and directed use of natural resources (Pickrill

and Todd, 2003), and has opened lines of scientific inquiry previously limited by the

technology available (Wright, 1999; Andersen et. al., 2005; Leimgruber et. al., 2005).

In the sea, detailed surveys have been conducted through the use of multi-beam

sonar systems (Verlaan, 1997; Pickrill and Todd, 2003) as well as the LIDAR (Laser

Imaging Detection and Ranging) optical system (Kincade, 2003). Coupled with

Geographic Positioning Systems (GPS), data can be placed very precisely in a spatial

context. Such detailed information has already demonstrated its utility in the

management, exploration, and understanding of the marine environment. In coastal

environments, decisions regarding location of sewage outfalls as well as cable and pipe-

line routes have been well founded (Pickrill and Todd, 2003). Side-scan sonar has been

used to identify mineral deposits on the ocean floor (Lee and Kim, 2004) and investigate









the geo-physical properties of hydrothermal vents and areas of sea-floor spreading

(Wright, 1999). In fisheries, LIDAR has been combined with video technology for the

remote sensing of schools of capelin (Mallotus villosus) and zooplankton densities

(Brown et. al. 2002). Detailed maps were created of Brown's Bank in the Northern

Atlantic, which were then coupled with biological data to identify key scallop habitats

(Kostylev et. al., 2003). As a consequence, commercial trawlers were able to reach

quotas in as little as one quarter the time while avoiding fragile or unproductive regions

(Pickrill and Todd, 2003).

The availability of such detailed geographic data is clearly a boon to resource

managers and those working in the natural environment. Mack (1990) noted, however,

that there are unintended uses of new technologies that may only become apparent once a

program is well underway. For example, fishery resources are inherently patchy in space,

and detailed geographic information collected to other ends has the potential to facilitate

their exploitation. In the example of the commercial scallop fishery on Brown's Bank

(Kostylev et. al., 2003; Pickrill and Todd, 2003), a quota limited the harvest. New

technologies provided information facilitating more efficient harvest without increasing

the overall effect on the fishery, and possibly minimized impacts to benthic habitats by

reducing the area trawled. Had there been no quota, continued efficient and directed

efforts could have led to much greater yields and thus potential overexploitation in the

fishery. The development of information increasing the potential for efficient

exploitation of natural resources, if not coupled with proper management strategies,

creates the possibility of over-exploitation of those resources.









Like the scallop, many marine fishery species are associated with specific habitat

types. The current efforts in sea-floor mapping hold the potential of identifying and

describing those habitats in great detail, leading to far better understanding of population

distributions and identification of essential fish habitats. While clearly useful to

managers, to date, there are few documented examples of how fishermen use detailed

geographic information of fish habitat. Identification of densely populated habitat among

recreational fishermen is commonly achieved through large expenditures of effort in

exploring new areas and searching with the limited bottom mapping information and

technologies available to the recreational sector. Due to the investment in locating

fishing sites, once found, such areas are rarely made public. Although maps are created

and bathymetric data are available to recreational anglers, they are typically of coarse

scale and limited scope.

The Ideal Free Distribution (IFD), as applied to the distribution of angling effort

(Walters and Martell, 2004), predicts that effort will be directed to the most profitable

fishing grounds. One assumption of the IFD is complete knowledge of fishing grounds

and the relative profitability of each. Increase in awareness of available fishing grounds,

as is made possible by detailed bottom mapping, will likely lead to a distribution of

angling effort closer to that predicted by the IFD. The predicted consequences are an

increase in catch-per-unit-effort (CPUE) in the short-term, and hyper-stability in the long-

term as detailed geographic information facilitates exploitation in the face of declining

stocks.

Due to the expanse of marine environments and limited ability of recreational

anglers to accurately perceive the sea floor, habitat extent is likely a key factor in









determining its probability of discovery. Small, isolated habitat patches that support

dense local populations of fish are difficult to locate by conventional means, rarely shared

if they are discovered, and are likely key habitat features providing refuge for targeted

marine species. The uncontrolled dissemination of fine-scale bathymetry could reveal

such locations in detail, leading to better-directed and more efficient exploitation of

stocks that are patchy in space.

The importance of such refuges is largely unknown, but is potentially critical in the

maintenance of a viable fishery. The impacts of both recreational and commercial fishing

on populations and assemblages of marine fish have been well documented (Haedrich

and Barnes, 1997; Wantiez et. al., 1997; Bianchi et. al., 2000; Roberts et. al., 2001;

Bremner et. al., 2003; Coleman et. al., 2004). Fishing generally leads to fewer and

smaller fish of the targeted species (Haedrich and Barnes, 1997; Grandcourt, 2003) as

well as reduced overall diversity (Albaret and Lae, 2003; Ley et. al., 2002). Protection

from fishing, in some cases, has reversed these trends (Roberts, 1994; Wantiez et. al.,

1997) and resulted in increased abundance and size of targeted fish as well as increased

biodiversity in protected areas. Refuges provide fish the opportunity to become older and

larger. Such individuals are of great importance to the welfare of a fishery (Birkeland

and Dayton, 2005). For some species, larger and older individuals have been shown to

have exponentially higher fecundity (Berkeley et. al., 2004a) and to produce healthier,

faster-growing larvae (Conover and Munch, 2002; Berkeley et. al., 2004b), as well as

preserving genetic diversity (Hauser et. al., 2002).

As large-scale sea-floor mapping programs are relatively new, studies of such

natural, small, isolated, but high quality, habitat features are rare. The use of artificial









reef structures to create such locales provides the opportunity to control for habitat

features (size, shape, and distribution) that may influence the resulting assemblage of

species as well as the exploitation of the resident species by fishers.

The specific characteristics of artificial habitat along with reef placement (Coll et.

al., 1998) strongly influence the resulting assemblage of marine life. There are two

characteristics of artificial reef use by marine fish that have been widely studied: as

shelter and as a food source. Available refuge has been demonstrated to be the dominant

structuring influence on the species resident on a reef (Williams and Sale, 1981; Doherty

and Sale 1985; Sweatman, 1985; Hixon and Beets, 1989; Eklund, 1997; Lindberg in

press) although resident species clearly use the reef as a forage base (Herrera et. al., 2002;

Szedlmayer and Lee, 2004). Many top-level predators are transient groups (e.g., jacks,

sharks, tunas, mackerels) and would be less-frequently observed at artificial reefs despite

their potential for playing a major role in the structuring processes of the resident fish

assemblage (Bohnsack et. al., 1994; Carr et. al., 2002).

The use of artificial reefs as refuge is dependent on the shelter characteristics of the

structure provided. Many studies have investigated the effects of reef size and design on

resulting fish assemblages. Several general trends have been observed. Larger reef

structures support higher abundances of fish (Rountree, 1989; Lindberg and Loftin, 1998)

though not necessarily at higher densities (per unit reef area) (Bohnsack et. al., 1994;

Lindberg and Loftin, 1998). Bohnsack et. al. (1994) found that although there are lower

densities at larger reefs, the resident fish are larger on average than on smaller reefs. In

contrast, Lindberg et. al. (in press) observed higher growth rates by gag, Mycteroperca

microlepis, on smaller artificial reef patches. These patterns are likely dependent on the









species and system being studied. Size of refuges within a reef has been shown to

positively influence the abundance of fish suited to the size of refuge provided (Frazer

and Lindberg, 1994; Hixon and Beets, 1989; Hart, 2002). Fish tend to prefer openings

close to their own body size (Shulman, 1984). Within reefs, higher habitat complexity

increases diversity of the resulting assemblage as adequate shelter is provided for a larger

range of species (Charbonnel et. al., 2002; Sherman et. al., 2002; Gratwicke and Speight,

2005). Although resident species also use the reef and surrounding area as a forage base

(Herrera et. al., 2002; Szedlmayer and Lee, 2004), several studies have concluded that

refuge is the over-riding factor determining abundance of resident fish on artificial reefs

(Ecklund, 1997; Lindberg et. al. in press).

For recreational anglers, artificial reefs are widely-known and publicized, easily

locatable angling sites. In public surveys, 6.4% (McGlennon and Branden, 1994) to 87%

(Ditton and Graefe, 1978) of anglers reported fishing on artificial reefs. The lower end of

the spectrum resulted in a fishing intensity (angler hours/unit area) 92-171 times greater

than observed on natural substrates (McGlennon and Branden, 1994). While

expectations of high catch rates are a motivating factor for selecting artificial reefs

(Milon, 1989) only 5 of 27 comparisons by McGlennon and Branden (1994) yielded

significantly higher catch rates on artificial habitats, and these were all for pelagic

species. Solonsky (1985) demonstrated the significant impact that anglers can have on

recreationally targeted game fish on an artificial reef in Monterey Bay. One central reef

amidst several others was marked for recreational fishing. After three years, there were

significantly fewer rockfish on the marked reef relative to the unmarked reefs

surrounding it. Furthermore, tagged fish on the surrounding reefs were observed to move









onto the marked reef, but none were observed leaving the marked reef, demonstrating the

function of a known artificial reef to attract fish thus increasing their vulnerability to

fishing. Turpin and Bortone (2002), who observed artificial reefs before and after they

were displaced by hurricanes, also observed a significant increase in lengths of gag, and

red snapper, Lutjanus campechanus, on these reefs following displacement as anglers no

longer knew their locations. The use of artificial reefs in the study reported here offers

the additional dimension of high attraction for recreational anglers.

The purpose of this study was to test how the public release of detailed location

information regarding patchy habitat impacted the standing stock of gag, a dominant reef-

associated, recreationally-targeted species. The specific objectives were: (1) to determine

how publication of reef locations to anglers differentially affected abundances of both

legal and sub-legal gag across different reef architectures (sizes and spacings), and (2) to

determine the impacts of angling over a broad time-scale, including the discovery and

exploitation of unpublished reef locations. This evaluation of angling impacts as a

function of habitat patchiness and location information provides fishery managers with

experimental results pertinent to the management of fisheries in light of the ever-

increasing efficiencies that anglers garner through new and developing technologies.

Publication was predicted to lead to rapid reductions of legal gag. A refuge effect

on more-widely spaced patches was predicted as these are more difficult to fish as a

single unit. Angling impacts were predicted to be greatest on 16-cube arrays as anglers

are likely to favor these under the conception that larger habitat patches hold more fish.

Discovery of unpublished arrays was expected to be a function of both patch size and

spacing. Larger and more-widely spaced patches provide the greatest probability of






8


encounter for searching anglers. Discovery of a single patch should lead to discovery of

the entire array as anglers were aware of the reef layouts within the experimental system.

Several mechanisms likely affect sub-legal gag abundance. Compensatory responses to

predicted decreases in legal gag abundances would lead to an increase in sub-legal gag

abundance. Induced immigration and mortality from catch and release would lead to

declines in sub-legal gag abundance. Large, closely-spaced arrays were predicted to have

the highest fishing effort, thus they were expected to demonstrate the relative importance

of these mechanisms.














CHAPTER 2
METHODS

Experimental System

The Suwannee Regional Reef System (SRRS) was constructed from 1990 to 1993

in the northeastern Gulf of Mexico, approximately 20-25 km from the mouth of the

Suwannee River (Figure 1A). The building blocks of the SRRS were 89 cm x 89 cm x 89

cm concrete cubes with 60 cm diameter, cylindrical horizontal passages through the

centers and 10 cm diameter, horizontal, right-angle tunnels through each of the eight

corners (Figure 1B). Cubes were arranged in either 4-cube or 16-cube square reef

patches, such that central passages all run in the same direction. Patches were arranged

hexagonally, and were spaced 25, 75 or 225 m apart, constituting a reef array (Figure

1B). Reef arrays were spaced one to two km apart along the 13 m depth contour.

Twenty-two arrays comprise the entire SRRS, which was designed as a 3 x 2 factorial

experiment with three spacing treatments (25m, 75m, 225m) and two patch size

treatments (4-cube and 16-cube).

The SRRS was twice affected by perturbations in its initial years. In 1992,

locations of four arrays were inadvertently published. In 1995, all fish on the five

southernmost arrays were eliminated by a red tide event. This fish-kill effectively reset

the fish colonization process on those arrays. Two arrays were both published

inadvertently and experienced the fish-kill.

In November of 1996, locations of two to three arrays per treatment group were

published for access by the general public. No locations of the 75 m spaced arrays were









published and thus the 75 m treatment was excluded from this study. The early

perturbations and requirements of other on-going research projects warranted restrictions

on randomization when selecting arrays for publication, e.g. inadvertently published

arrays were assigned to the 'published' treatment.

Study Organism

Gag, Mycteroperca microlepis, is a dominant reef-associated, demersal fish species

in the Western Atlantic ranging from New England to Brazil, including the Gulf of

Mexico (McErlean, 1963). As protogynous hermaphrodites, female gag mature at 3-6

years old and 538 to 795 mm TL (Hood and Schlieder 1992; Harris and Collins 2000). In

two studies, no males younger than five or smaller than 875 mm TL were observed

(Hood and Schlieder 1992; Harris and Collins 2000). By age 11, males comprised 50%

of the age class. Transition from female to male is hypothesized to be socially mediated

(Koenig et. al. 1999; Coleman et. al. 2002) but is debated (Kenchington, 1999). Gag

reach sizes between 1100 and 1200 mm and ages ranging into the early twenties (Hood

and Schlieder 1992; Collins et. al. 1998).

Gag form spawning aggregations of 10's to 100's of individuals (Coleman et. al.,

1996). Aggregations have been observed along the shelf edge break in the Northwest

Gulf of Mexico in 50-120 m (Coleman et. al. 1996; Koenig et. al., 1999), on deep (70-

100 m) reefs off the Atlantic coast of Florida (Gilmore and Jones, 1992), and have been

recently reported on the Campeche Bank, Yucatan, Mexico (Brule et. al., 2003). Gag

spawn from late December through April with peak spawning in February and March

(Hood and Schlieder 1992; Collins et. al. 1998). Currents carry gag larvae inshore where

they settle in seagrass beds and oyster bars (Ross and Moser, 1995). Average larval

duration is approximately 43 days (Keener et. al. 1988). Gag spend their first summer









growing in inshore habitats where their diet is composed primarily of crustaceans

(Bullock and Smith 1991; Weaver 1996). In the late summer and fall, gag move to

deeper water and take up residency on near-shore reefs and live-bottom where their diet

shifts to decapod crustaceans and fishes (Bullock and Smith 1991; Weaver 1996). It is in

these habitats that gag reach legally harvestable size and are first targeted by fishers. Gag

continue to grow and mature in these environments before moving to spawning grounds

as mature adults. The natural annual mortality rate is unknown but is assumed to be

M=0.15 for stock assessment purposes (Turner et. al. 2001). It is during their transition

across the shallow continental shelf that juvenile to sub-adult pre-reproductive females

take up residency on the SRRS

Sources of Data

Gag present on each SRRS patch were counted once each Summer from 1995 to

1998 and 2002 to 2004 by trained SCUBA divers (see Lindberg et. al., in press for

details). Types of data collected changed over the years of sampling as the research

questions being addressed changed. I worked with a historical data set (1995 to 1998)

and participated in data collection during the 2002 to 2004 period. From 1995 to 1996

the total number of gag on each patch reef were counted and divers visually estimated the

length of the largest and smallest gag as well as the average size of gag. In 1997 and

1998, counts were divided into total number of legal ( >20" or 508 mm) and sub-legal

(<20" or 508 mm) gag. In 2002 through 2004, gag were individually assigned to 10 cm

size groups. The 50-59 cm size group was further divided into gag from 50-55 cm and

56-59 cm in order to determine the number of legal and sub-legal gag on a patch. This

coincided with an increase in the legal size of recreationally harvestable gag from 20"

(508 mm) to 22" (559 mm) that occurred on June 19, 2000 (Turner et. al., 2001). For this









investigation, all data were converted to counts of legal and sub-legal gag by array.

Legal and sub-legal counts were estimated for 1995 and 1996 from percentages of legal

and sub-legal gag observed on unpublished arrays of the same architecture in 1997. This

is based on a necessary assumption that the proportions of legal and sub-legal gag on

patches of like architecture and presumed level of fishing effort is consistent over time

(1995-1997) and space (among unpublished arrays). These approximations were further

adjusted based on the size estimates for the largest and smallest gag (i.e., if the largest

gag observed was smaller than the legal limit, all gag were considered sub-legal). Patch

reef counts were summed for each array, as the arrays rather than the patches are the

proper replicates for this study.

Suitability of Data

Preliminary analyses were conducted to establish the suitability of data to be used.

Reef arrays were constructed from 1990-1993. Within arrays, data from 1995 and 1996

were compared for significant differences. None were found and thus variable reef age

was determined not to be a significant factor influencing gag abundances. In 1995 a fish-

kill event eliminated all fish on the five southern-most reef arrays. The fish-kill was

investigated as a treatment effect within reef architectures. Data were excluded from the

final model for all architecture/year combinations in which the fish-kill treatment was

significant. This resulted in the exclusion of data from all fish-killed arrays in 1995. In

1996 legal counts on four-cube arrays were considered recovered and included in further

analyses. Analysis indicated all affected arrays had recovered by 1997. In 1992, several

array locations were inadvertently published. Due to low replication and the impacts of

the fish-kill, I was unable to evaluate this effect.









Experimental Design

Three variables were investigated in a repeated measures 2 x 2 x 2 x 3 factorial

design for their effects on gag abundance on the SRRS: patch spacing (25 m or 225 m

between patches within an array), patch size (4 or 16 cubes per patch), publication of

locations for public fishing (published or not), and time period. Annual counts were

nested within three different time periods (time relative to the publication of array

locations). "Pre" consists of data collected in 1995 and 1996, prior to publication.

"Acute" consists of data collected in 1997 and 1998, the period immediately following

publication. "Chronic" consists of data taken in 2002 through 2004, six to eight years

following publication.

Statistical Analyses

All analyses were conducted independently on legal and sub-legal gag count data.

To satisfy the assumptions of normality and homogeneity of variances, all count data

were square root transformed.

Data not excluded by the preliminary analyses were entered in a four-way repeated-

measures, mixed-model Analysis of Variance (ANOVA) to determine significant

interactions and main effects. Alternate correlation structures for the effect of year nested

within period were tested, but none improved the model over a zero-correlation model.

The Kenward-Rogers method was used to estimate the degrees of freedom for the

appropriate F-test for fixed effects. Follow-up analyses were done by pair-wise

comparisons of least square means provided for each treatment by the model. Residuals

were plotted in a Q-Q plot and against predicted values to examine model fit. Akaike's

information criterion as well as mean square error values were compared between

treatment levels to investigate error structure in the model. All statistical analyses were






14


performed in SAS version 8 (SAS Institute Inc. 2002, Cary, NC). An alpha value of 0.05

was used for determining statistical significance. Due to the low replication and thus low

suspected power of these tests, the alpha value was not adjusted to maintain an

experiment-wise error rate of 0.05.











A


N '-


*



Keys
30' 20 10' 83' 50' 40'

B



0000
array pC-


25-mrn, 75-m
or 225-m
spacing

S-89 cm-1
4-cube ",
array "',D0






Figure 1. Design of the Suwannee Regional Reef System (A) Location of SRRS in the
Big Bend region of Florida (inset). (B) Design of a component artificial reef
block and layout of an SRRS array.














CHAPTER 3
RESULTS

Legal Gag

The four-way interaction of patch size, patch spacing, publication and time period

was significant (p=0.0083, Table 2) for legal-sized gag abundances on the SRRS. The

results of follow-up comparisons below explain this four-way interaction. The

interaction is partitioned chronologically with steady-state comparisons within time

periods and transitional comparisons between time periods. Mean square errors were

examined between treatment levels and determined not to be significantly different

between levels of any treatment. Residual analysis indicated good model fit. The

significant model was run using untransformed data in order to generate least square

means and error estimates for use in figures to better convey the results.

Pre-publication Time Period (Initial Conditions)

Arrays were not selected randomly for publication and thus there were pre-existing

differences between arrays selected for the published and unpublished treatments. Arrays

that experienced the fish-kill and those that were inadvertently published were given

priority as 'published' treatments in order to maintain a valid 'unpublished' treatment to

compare against. To-be-published 4 x 225 m arrays had significantly fewer legal gag

than their not-to-be-published counterparts even before their publication (p=0.0008).

Beyond the perturbations, there was a distributional pattern on the unpublished

arrays dependent on the size and spacing of arrays (Figure 2). Within spacing treatments,

16-cube arrays had a higher abundance of legal gag than 4-cube arrays (25 m p=0.0002;









225 m p=0.0009). Within 4-cube arrays, there was a higher abundance of legal gag on

225 m arrays than 25 m arrays (p=0.0314).

Transition from "Pre" to "Acute" Time Periods

The publication of array locations significantly impacted the abundances of legal-

sized gag for 16-cube arrays (Figure 3) for both spacing treatments (25 m p<0.0001; 225

m p<0.0001). Four-cube published arrays, however, did not change significantly

following publication (25 m p=0.3378; 225 m p=0.3898), (Figure 4). There was a

significant increase in legal gag abundance on unpublished 4 x 25 m arrays (p=0.0071),

and thus no difference in the "acute" period between unpublished 4-cube arrays based on

their spacing (p=0.6264). This was the only significant change on any of the unpublished

array treatments.

Within "Acute"

The effect of publication on legal gag was most pronounced for arrays with larger

reef patches (Figure 5). The number of legal gag on published 16-cube arrays, however,

was not significantly different than the number of legal gag on published 4-cube arrays

(25 m p=0.5977; 225 m p=0.2462) or unpublished 4-cube arrays (25 m p=.0004 [greater

abundance on four-cube arrays]; 225 m p=0.2380). Unpublished arrays maintained the

size-dependent difference of more legal gag on 16-cube than 4-cube arrays (25 m

p=0.0005; 225 m p<0.0001). In the "acute" period a pattern emerged of more legal gag

on unpublished 4-cube arrays relative to published 4-cube arrays for both spacing

treatments (25 m p=0.0044; 225 m p=0.0249). More widely spaced arrays were

hypothesized to be more difficult to fish and although there were more legal gag on

published 16-cube arrays at the 225 m spacing, the difference was not significant

(p=0.0737).









Transition from "Acute" to "Chronic"

Following the initial impacts of publication observed in the "acute" period, none of

the published arrays experienced significant changes (Figures 3 and 4). On unpublished

arrays, decreases indicative of discovery by anglers were observed. Although 4-cube, 25-

meter arrays did not change (p=0.2764), 4-cube arrays at the 225-meter spacing declined

significantly (p=0.0483) (Figure 4). Sixteen-cube arrays experienced a significant

reduction in legal gag between the "acute" and "chronic" periods at both spacing

treatments (25m p=0.0010; 225m p<0.0001) (Figure 3).

Within "Chronic"

Despite the decrease on unpublished 16-cube, 25 m arrays, these arrays still held

significantly more legal gag in the "chronic" period than did the published 16 cube, 25 m

arrays (p=0.0003) (Figure 6). Reductions on unpublished arrays lead to there being no

difference in legal gag abundances between 16-cube, 225 m arrays and their published

counterparts (p=0.0872). Sixteen-cube arrays, both published and unpublished, did not

show any difference by spacing (pub, p=0.1246; unpub, p=0.4132).

Four-cube arrays showed a different pattern of gag abundance in the "chronic"

period than the "acute." Although there were still more legal gag on the unpublished 4-

cube, 25 m than the published 4 cube, 25 m arrays (p=0.0214), 4-cube, 225 m arrays

showed no difference between published and unpublished treatments (p=0.7808) (Figure

6). As with the 16-cube arrays, this was the result of a significant decrease on the

unpublished arrays. Within publication treatments, spacing was not significant on 4-cube

arrays (published p=0.4519; unpublished p=0.0872)

In the "chronic" period, patch size was no longer significant for any treatment.

Effects of publication continued to be significant for 25 m arrays (4-cube p=0.0214; 16-









cube p=0.0003), however, 225 m arrays no longer showed any differences by publication

(4-cube p=0.7808; 16-cube p=0.1812)

Sub-Legal Gag

There was a significant main effect of time period (p<0.0001) for sub-legal gag

(Table 4). The three-way interaction between publication, patch size, and patch spacing

was also significant (p=0.0513) (Table 4) given the low replication and thus low expected

power of this test. Mean square error was examined between treatment levels and

determined not to be significantly different between levels of any treatment. Residual

analysis indicated good model fit. The significant model was run using untransformed

data in order to generate least square means and error estimates for use in figures to better

convey the results.

The significant main effect of time period was manifested as a trend of decreasing

abundance of sub-legal gag. Although the decrease was not significant from the "pre" to

the "acute" period (p=0.5617), it was significant from "acute" to "chronic" (p=0.0001).

The significant effect of publication in the three-way interaction was only on 16-

cube, 25 m arrays. There were more sub-legal gag on the unpublished than published

arrays (p=0.0151) (Figure 7).

In most cases, there were more sub-legal gag on 16-cube arrays than on 4-cube

arrays. This held true for unpublished arrays (25 m p=0.0101; 225 m p=0.0017) as well

as published 225 m arrays (p=0.0003), but not for published 25 m arrays (p=0.6966).

Patch spacing had the most involved interaction determining sub-legal gag

abundance (Figure 8). There was a significant interaction with publication as spacing had

no significant effect on unpublished arrays (4-cube p=0.3868; 16-cube p=0.5679). Patch

spacing and patch size interacted to affect patterns of sub-legal gag abundance on






20


published arrays. There were more sub-legal gag on published 16-cube arrays at the 225

m spacing than the 25 m spacing (p=0.0125). The opposite was true for the published 4-

cube arrays with more sub-legal gag on 25 m arrays than 225 m arrays (p=0.0188).









Table 1. Type 3 tests of fixed effects for legal gag
Covariance Parameters Subject Estimate Std. Err. Z value Pr Z
Reef 1.1787 0.6847 1.72 0.0462
Year (Period) Reef 2.3078 0.3555 6.49 <0.0001

Four-way interaction Num DF Den DF F-value Pr>F
Pd*Fishing*Size*Dist 2 85.3 5.08 0.0083

Three-way interactions Num DF Den DF F-value Pr>F
Pd*Fishing*Size 2 85.3 15.85 <0.0001
Pd*Fishing*Dist 2 85.3 4.01 0.0217
Pd*Size*Dist 2 85.3 2.72 0.0716
Fishing* Size*Dist 1 10.5 1.59 0.2344

Two-way interactions Num DF Den DF F-value Pr>F
Pd*Fishing 2 85.3 27.51 <0.0001
Pd*Size 2 85.3 36.64 <0.0001
Pd*Dist 2 85.3 6.21 0.0030
Fishing*Size 1 10.5 3.22 0.1014
Fishing*Dist 1 10.5 0.60 0.4549
Size*Dist 1 10.5 4.39 0.0613

Main Effects Num DF Den DF F-value Pr>F
Period 2 85.3 39.43 <0.0001
Fishing 1 10.5 48.20 <0.0001
Size 1 10.5 43.84 <0.0001
Distance 1 10.5 4.19 0.0664









Table 2. Type 3 tests of fixed effects for sub-legal gag.
Covariance Parameters Subject Estimate Std. Err. Z Value PrZ
Reef 1.0481 0.7444 1.41 0.0795
Year (Period) Reef 3.6065 0.5661 6.37 <0.0001

Four-way interaction Num DF Den DF F-value Pr>F
Pd*Fishing*Size*Dist 2 83.9 1.53 0.2222

Three-way interactions Num DF Den DF F-value Pr>F
Pd*Fishing*Size 2 83.9 2.75 0.0695
Pd*Fishing*Dist 2 83.9 1.25 0.2928
Pd*Size*Dist 2 83.9 1.24 0.2937
Fishing* Size*Dist 1 10.5 4.83 0.0513

Two-way interactions Num DF Den DF F-value Pr>F
Pd*Fishing 2 83.9 0.50 0.6088
Pd*Size 2 83.9 2.88 0.0615
Pd*Dist 2 83.9 0.24 0.7852
Fishing*Size 1 10.5 1.34 0.2719
Fishing*Dist 1 10.5 0.01 0.9252
Size*Dist 1 10.5 13.23 0.0042

Main Effects Num DF Den DF F-value Pr>F
Period 2 83.9 12.44 <0.0001
Fishing 1 10.5 4.15 0.0675
Size 1 10.5 38.63 <0.0001
Distance 1 10.5 0.02 0.8831











250


S200
I-,



[] i16-cube
100

50
0 5

25 225
Distance Between Patches (m)



Figure 2. Pre-publication distribution of legal gag grouper on the SRRS. Data are drawn
from not-to-be-published arrays due to the influence of pre-publication
perturbations on to-be-published arrays.


250


S200 x

150 -.,.-Pub, 25m
S150
T--ime- Pub, 225m
S architecUnpub, 25m
8 100oo ,,
S1 0---x--- Unpub, 225m

50-..----,----



Pre Acute Chr
Time Period

Figure 3. Chronology of impacts to legal gag on 16-cube arrays of the SRRS by array
architecture and publication status.





















46.




Pre Acute Chr
Time Period


- -- Pub, 25m
- -- Pub, 225m
-A-Unpub, 25m
--X- --Unpub, 225m


Figure 4. Chronology of impacts to legal gag on four-cube arrays of the SRRS by array
architecture and publication status.


250


200


~150
15. Published
0 O] Unpublished
100


50 T


0
4x25m 4x225m 16x25m 16x225m
Array Architecture

Figure 5. Abundance of legal gag per array within the "acute" period by array
architecture and publication status.











100
90
80
L 70
60
S- Published
S 50
CD ] Unpublished
3 40
S30
0 20

10
4x25m 4x225m 16x25m 16x225m
Array Architecture

Figure 6. Abundance of legal gag per array within the "chronic" period by array
architecture and publication status.


250


200


150
l Published
O Unpublished
100 H


50 -


0
4x25m 4x225m 16x25m 16x225m
Array Architecture

Figure 7. Abundance of sub-legal gag per array, by array architecture and publication
status, averaged across all time periods.











A. Published Arrays

250

200

150 -25m

o 100 225m

S50 -

CO 0
4 16
Patch Size


B. Unpublished arrays

250

200 T

"150 25m

100 0 225m
'7,
50 -
0
CO 0
4 16
Patch Size

Figure 8. Abundance of sub-legal gag per array, by array architecture on (A) published
and (B) unpublished arrays.














CHAPTER 4
DISCUSSION

The SRRS was designed to examine how spatial components of habitat structure

affect gag abundance. The subsequent publication of several array locations introduced

directed fishing effort as an additional factor. Although no data were collected regarding

fishing effort or angler behavior, differences between published and unpublished

treatments are assumed to be due to directed fishing. Further, inferences are possible

regarding angler behavior based on observed gag abundances on the SRRS. In a survey

of recreational anglers in Dade County, FL, over 28% used artificial reef sites, motivated

by expectations of high catch rates (Milon, 1989). Fishing effort usually is positively

related with fish abundance that "represents a cumulative statistical summation of the

effects of individual fisher choices" (Walters and Martell, 2004, p.205). For recreational

anglers this leads to a roughly linear relationship between fish abundance and angling

effort (Walters and Martell, 2004). On the SRRS this relationship is complicated by the

rapid depletion of localized standing stocks of legal gag. The reduction in abundance

lowers the benefit to anglers of selecting particular arrays and offers feedback to their

decision-making process, but must have a lag as new experiences are likely slow to

modify initial impressions and expectations.

This experiment effectively demonstrated the ability of anglers to remove the vast

majority of legally harvestable fish from published artificial reefs over the course of only

a few years. Once published, size of reef patches had no impact on abundance of legal

gag, indicating both large and small patches were fished down to a similar level. Over









the six to eight years following publication and the initial rapid reductions in legal gag,

effort was apparently redirected to locating unpublished reef arrays. Changes on

unpublished reef arrays can likely be attributed to discovery by anglers as they were

proportional to predicted impacts based on architecture. Large and widely-spaced

patches (those most prone to discovery) experienced declines in abundance, while reef

arrays composed of small closely-spaced patches did not change. Patterns in sub-legal

gag abundance are driven by significant declines on the most heavily fished arrays

(published, 16-cube, 25 m spaced).

Several studies have reported higher abundances of fish on larger habitat patches or

patches providing more refuge (de Boer 1978; Roberts and Ormond 1987; Hixon and

Beets, 1989; Rountree, 1989; Kuwamura et. al. 1994, Eggleston et. al. 1998; Abelson and

Shlesinger 2002). The initial conditions observed on the SRRS with regard to array

architecture are thus not surprising. Studies of gag home range on the SRRS (Kiel 2004)

and residency (Lindberg et. al. in press) have indicated that reef patches spread 25 m

apart are collectively used as a single home-site whereas 225 m spaced patches are used

independently.

The fact that fishing had both an immediate and significant impact on the largest

aggregations of gag is not surprising. Reductions in catch assumed to be reflective of

similar reductions in abundance were observed by Grandcourt (2003) in monitoring the

exploitation of a virgin stock of crimson jobfish, Pristipomoidesfilamentous, a shelf-edge

hook and line fishery. There are also numerous examples in the literature of comparisons

between both recreationally and commercially fished and un-fished areas in which there

are more fish and larger fish in protected areas than unprotected ones (Roberts, 1994;









Jennings and Polunin, 1996; Wantiez et. al., 1997, Guidetti et. al., 2005, Kamukuru et.

al., 2005) as well as declines over time of exploited stocks (Haedrich and Barnes, 1997;

Fogarty and Murawski 1998; McClanahan and Mangi, 2001; Albaret and Lae 2003;

Laurans et. al., 2004). Solonsky (1985) demonstrated the significant impact of fishing on

artificial reefs in Monterey Bay, CA. A single marked reef was constructed amidst other

unmarked reefs. Observed abundance of legal-sized rockfish on the marked reef was

reduced after three years of fishing effort relative to the unmarked reefs. Furthermore,

tagged fish were observed to move from unmarked reefs to the marked reef, but not vice

versa, indicating the potential 'sink' quality of a fished artificial reef. Similar movements

of fish (from natural to artificial reefs, but not back) were observed in Puerto Rico (Fast

and Pagan, 1974). On the SRRS we had the unique opportunity to examine the manner in

which variable spatial qualities of reefs interact with fishing effort to determine the

abundance of a targeted species.

Although 25 and 225 m published 16-cube arrays experienced significant declines

in abundance of legal gag following publication, the predicted refuge effect of more

widely spaced arrays was only marginally significant in the "acute" period. There are

several potential mechanisms for such a refuge effect. Since gag treat 25 m arrays as a

single home-site, fishing effort, even when focused on a single patch, is effectively

fishing the entire array due to the movement of gag among patches. There is also a

significant margin of error for non-anchored fishing techniques (drift-fishing or trolling)

on 25 m arrays. Should the boat's course not take it over the intended patch, it is far

more likely to encounter gag on another patch, or between patches. Furthermore, 25 m

spaced arrays are likely to be more appealing to spear-fishermen who can easily swim









between patches in search of legal gag. All of these factors likely contribute to higher

attractiveness to anglers of 25 m arrays relative to 225 m arrays. An additional

consideration is that 225 m spaced patches may recruit more gag as a result of their larger

footprint, simply by an increased chance of encounter by gag, however, immigration rates

and residence times under fished conditions, relative to removal rates by anglers are

unknown.

While the publication of array locations led to a rapid depletion of legal gag on 16-

cube patches, 4-cube patches did not change significantly with publication. Both their

smaller size and lower abundances of gag make them more difficult to locate and fish

effectively. Furthermore, the four cube arrays were likely less attractive to anglers based

on the common conception that smaller reefs hold fewer fish. Although there was no

significant change on the published four-cube arrays between the "pre" and "acute"

periods, there was a significant effect of publication within the "acute" period (more legal

gag on unpublished arrays). Keeping in mind that there were randomization restrictions

in assignment of publication treatments because of earlier perturbations, the effect of

publication on four-cube arrays may have been to maintain low abundances on these

arrays, rather than to depress them below their pre-publication levels.

The immediacy of the decrease in gag abundances following publication is further

emphasized by the fact that none of the published treatments demonstrated any

significant further decreases between the "acute" and "chronic" periods. A new

equilibrium abundance appears to have been reached in which legally harvestable fish

were maintained at low levels by fishing activities. The increase in the minimum size of

recreationally harvestable gag between the "acute" and "chronic" periods had the









potential to further decrease abundances of legal gag as those between 508 and 550 mm

would be considered sub-legal in the "chronic" period. There was, however, a significant

decrease of sub-legal gag between these periods, indicating that this was a minimal effect

in relation to the other processes affecting abundances of legal and sub-legal gag on the

SRRS.

Because the SRRS represents only a way-point in the spatially stage-structured life

history of gag, there is a constant immigration to and emigration from the reefs. In

studies done prior to introducing the publication treatment, mean residence time for an

individual gag was 9.8 months (Lindberg et. al. in press). It is assumed that newly

arriving gag make a decision as to whether to stay or not based on current conditions on

the patch. Although density-dependent habitat selection has been confirmed for gag

(Lindberg et. al., in press), the exact influence of the standing stock of gag on an array in

the decision making process of newly arriving gag is unknown. On arrays depleted by

fishing, it seems reasonable that newly arrived legal-sized gag would find themselves

among the dominant fish present and be more likely to stay on the reef than if there was a

full compliment of un-fished legal gag present. In this manner there may be a higher

percentage of newly arrived gag deciding to stay on published patches, thus making

themselves vulnerable to fishing, than on unpublished patches or patches prior to

publication. Fully understanding the rate at which gag arrive, and the proportion of those

taking up residence, as well as criteria important in making such a decision, would be a

big step forward in understanding the implications of fishing on habitat selection and

habitat-specific mortality risk.









The tendency of gag to aggregate in specific habitats known to recreational anglers

fits the definition of an 'ecological trap' (Schlaepfer et. al., 2002). The concept of

ecological traps has most widely been applied to terrestrial environments. Ecological

traps result when an organism makes a mal-adaptive habitat selection, due most

frequently to an anthropogenic change or manipulation of the environment, based on cues

that over evolutionary time were correlated with improved fitness. In the marine

environment, the tendency of many game-fish species to associate with structure can be

interpreted as an ecological trap. Once discovered by anglers, high quality habitat (both

artificial and natural) will continue to attract and aggregate both fish and the anglers

targeting them. In the case of the SRRS, the artificial reef patches are high quality habitat

(Lindberg et. al. in press) providing gag both refuge and a prey base. The outcome,

however, is an aggregation accurately predictable in space, leading to the removal of the

majority of legally harvestable gag. The decision to take up residence on published

patches of the SRRS seems to meet the criteria of an ecological trap (Schlaepfer et. al.

2002), but could only be conclusively defined as such with complete knowledge of the

overall reproductive success of gag taking up residence on the SRRS relative to those

inhabiting natural hard-bottom habitats.

One of the most telling results is the lack of any significant difference between size

treatments of both published and unpublished arrays during the "chronic" period. While

other factors such as catch-ability of legal gag and by-catch of under-sized gag factor into

the benefit to anglers of fishing an array, the primary focus is assumed to be harvest of

legal gag, and each size of reef provides similar potential harvest at its new equilibrium

abundance. This indicates that the additional shelter on 16-cube patches does not provide









gag any greater protection from fishing relative to the four-cube arrays. Also, when

constructing reefs for the benefit of the gag, the additional investment in construction

materials is not justified by its potential to house more legal gag under conditions where

recreational fishing will occur.

The predictable impacts of fishing on the SRRS extend beyond the published

arrays. Ultimately the unpublished arrays of the SRRS are all predicted to become

discovered. Thus the rate of progression from their un-fished state in the pre-publication

period and "acute" period to their moderately-fished state in the "chronic" period is an

indication of their combined ease of discovery and subsequent value as fishing sites.

Between the "acute" and "chronic" periods, unpublished 16-cube arrays, in both spacing

treatments, experienced significant declines in legal gag. This is believed to be due to

increased fishing effort, most likely from directed efforts in response to declining catches

on published arrays, but also possibly due to simple chance, to locate sites that were

known to exist. Sixteen-cube arrays would be the most susceptible to discovery as they

have a larger footprint than four-cube arrays, and larger aggregations of gag, thus

providing the largest targets for searching anglers. Of the four-cube arrays, only the 225-

meter spaced treatments showed significant effects of discovery. The probability of a

searching angler encountering an array is higher on more-widely and systematically

spaced arrays where there is likely less overlap of the areas used by gag on different

patches. As the types of array architectures within the SRRS were publicly known,

discovery of one patch within an array should be interpreted as discovery of the array as a

whole.









Impacts of directed fishing extended beyond the removal of legally-harvestable gag

to the sub-legal gag. All comparisons involving published, 16-cube, 25-meter arrays

demonstrated the impacts of fishing pressure on sub-legal gag. This treatment apparently

received the highest level of fishing effort and thus was the first to demonstrate effects of

that angling pressure trickling down to the sub-legal gag. First, there were more sub-

legal gag on unpublished arrays of this architecture than published arrays. Second, there

was no difference between this treatment and 4-cube, published arrays at the 25-meter

spacing. In all other treatment combinations, 16-cube arrays held more sub-legal gag

than 4-cube arrays as would be expected by the amount of shelter provided. Finally,

published, 25-meter spaced, 16-cube arrays had fewer sub-legal gag than the more

widely-spaced, published, 16-cube arrays, a pattern that was not observed among the

unpublished arrays. Hooking mortality, illegal harvest, and induced emigration are all

potential mechanisms by which sub-legal gag may be affected. No data were collected to

determine the relative importance of these mechanisms. Catch and release associated

mortality from recreational anglers has been measured to be as high as 20 % from

headboat fisheries (R. Dixon, NMFS, personal communication). These gag, however,

were caught from a minimum depth of 25 m where there is a greater effect of swim

bladder expansion than occurs on the SRRS in 13 m of water, and they were not followed

beyond release. Both depth-related effects as well as hooking effects contribute to

release mortality. In a study of depth-related capture-release mortality on gag, where gill

or gut-hooked fish were not included, no gag caught from 20 m of water showed any

adverse depth-related effects of being caught (C. Koenig, FSU, unpublished data).

Hooking mortality on another serranid, Epinephelus quoyanus, in shallow waters (<2m)









of the Great Barrier Reef, where depth related effects were not a factor, was found to be

highest at 5.1% when bait-fishing with single hooks (Diggles and Ernst, 1997). Actual

catch and release mortality on the SRRS is likely close to this figure, as bottom-fishing

with natural bait is a very common technique. It is likely that many legal gag are hooked

several times before being landed and that sub-legal gag are both hooked and landed

without being harvested from the system. Beyond hooking mortality, the role these

experiences play in modifying behavior and possibly residence times of surviving gag

may be of importance.

The main effect of time period on sub-legal gag abundance manifested itself in a

decreasing trend over time. The only significant change, however, was from the "acute"

period to the "chronic" period. The lack of an interaction with publication makes

interpretation somewhat troublesome. It is possible that there were simply several years

of smaller year-classes of gag colonizing the SRRS. The continued directed angling

efforts both on published and unpublished arrays following the "acute" period, however,

certainly contributed to the decline.

This study has revealed an interaction of spatial qualities of habitat and angling

pressure, mediated by detailed information of those habitat qualities, in determining local

abundances of a targeted reef-dependent species. The relative benefit to gag that occupy

small patches of artificial habitat are clear. Widely-spaced patches within an array

increase the probability of a single patch being discovered. Discovery of a single patch,

in this case, should lead to discovery of the array as a whole as anglers are familiar with

the layout of patches in the SRRS. While the end results have been demonstrated there is

still uncertainty in the precise mechanisms, and their relative importance, combining to









produce the observed patterns. Identifying and quantifying these mechanisms would be

important for applying the results of this study to management decisions for gag, other

fish and other systems. Additional information regarding the usage and opinions of the

SRRS in the angling community could validate several of the assumptions and inferences

made herein as well as increase the applicability of conclusions drawn in this study. The

publication of detailed geographic information in this case allowed anglers to select or

disregard fishing sites according to their expectations of success based on habitat

architecture. The continued development of such detailed information regarding natural

habitats will enhance efficiencies in the exploitation of natural resources.
















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BIOGRAPHICAL SKETCH


The author was born in Washington, D.C. During his early years he was fascinated

by the fish, frogs, turtles and insects that he caught and raised and watched in his

neighborhood streams and ponds. As early as pre-school he was the tender of the class

aquarium. His first exposure to the scientific method came from Stanley Edwards, his

science teacher from fourth through sixth grades. Mr. Edwards effectively conveyed his

own passion for the sciences and natural world.

During summer vacation following his sophomore year of high school, he began

volunteering for Dr. Marjorie Reaka-Kudla, a coral reef biologist at the University of

Maryland. Being invited on a two-week research trip to the Florida Keys as a 16-year-

old who was half way through high-school convinced him he was in the right field.

Involvement in her research continued through his high school years.

He attended the University of California at Santa Barbara from which he graduated in

1998 with a Bachelor of Science degree in aquatic sciences. After graduation he returned

to the University of Maryland, this time working with Dr. David Secor of the

University's Chesapeake Biological Laboratory. Following three years as a faculty

research assistant he decided to return to school in pursuit of a master degree. The

opportunity to again work beneath the water drew him to the University of Florida where

he studied under Dr. William J Lindberg.






45


Following graduation he has accepted a position in Gainesville, FL, with Golder

Associates, an environmental consulting firm.