1 EVALUATIN G HATCHERY PRODUCED FLORIDA LARGEMOUTH BASS Micropterus floridanus FOR FISHERIES MAN AGEMENT By MICHAEL DAVID MATTHEWS A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILL MENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2015
2 2015 Michael David Matthews
3 To my parents for their everlasting support and Dawn, Courtney and Nathan for the ir patience
4 ACKNOWLEDGMENTS My research was funded in part by a grant from the Florida Fish and Wildlife Conservation Commission (FWC) and by the Division of Freshwater Fisheries Management. As a full time employee of the FWC, and with permission and encouragement from Rick Stout and Jon Fury, I was allowed to advance my educ ation utilizing the tuition waiv er program. I thank my graduate advisor chair, Dr. Kai Lorenzen, and the four graduate committee co members, Dr. Cortney Ohs, Dr. Mike Allen, Dr. C olette St. Mary, and Mr. Wesley Porak for their time, respect, and assistance. I specifically thank Dr. Lorenzen fo r his willingness to accept me as a graduate student fully aware of my very demanding and unpredictable hatchery work schedule. My research needs would not have been possible without the assistance of Rick Stout in securing hatchery space and the data collection efforts of Joshua Sakmar, Tyler Ferguson, Taryn Garlock, and Christopher Monk. I would like to thank Brittany Reynolds, a volunteer USF student, for all of her assistance in field sampling. I also would like to thank my fellow FWC biologist Wesley Porak for his time spent on my committee and guidance in completing my dissertation, and James Colee for his explanations and review on st atistic al analysis Finally I would like to express my gratitude to my family for allowing me to finish a personal goal I set 15 years ago. I thank Dawn for her understanding of my time away from the family over this three and a half year process. I was humbled and amazed by the support and data collection assistance of my children Courtney and Nathan. Most importantly I would like to thank my parents for their guidance through the years. It will be my greatest achievement in life if my children consid er me half as great a mentor as my parents were to me.
5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 9 ABSTRACT ................................ ................................ ................................ ................... 11 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .... 13 The Florida Bass Hatchery Program ................................ ................................ ....... 15 Research Questions ................................ ................................ ............................... 25 2 COMPARISON OF INTENSIVE PELLET AND LIVE REARING ON FIRST YEAR POST RELEASE PERFORMANCE OF FLORIDA LARGEMOUTH BASS .. 28 Methods ................................ ................................ ................................ .................. 32 Hatchery and Production Protocols ................................ ................................ .. 33 Fish Treatment and Pond Preparation ................................ ............................. 35 Pond Sampling ................................ ................................ ................................ 37 Data Analysis ................................ ................................ ................................ ... 38 Results ................................ ................................ ................................ .................... 39 Water Quality and Vegetation Coverage ................................ .......................... 39 Survival/Mortality ................................ ................................ .............................. 40 Growth ................................ ................................ ................................ .............. 42 Discussion ................................ ................................ ................................ .............. 44 Survival/Mortality ................................ ................................ .............................. 44 Hatchery Reared Compared to Wild Survival ................................ ................... 50 Growth and Performance ................................ ................................ ................. 51 Potential Confounding Effects of Inter cohort Interactions and Drawdowns ..... 54 Utility for Culture Based Fisheries Management ................................ .............. 55 3 ANGLING VULNERABILTY OF PELLET AND LIVE HATCHERY REARED FLORIDA LARGEMOUTH BASS > 250 mm ................................ ........................... 73 Methods ................................ ................................ ................................ .................. 76 Results ................................ ................................ ................................ .................... 79 Discussion ................................ ................................ ................................ .............. 82
6 4 SIZE AND DENSITY DEPENDENT PROCESSES POST RELEASE AND THEIR IMPLICATIONS FOR OPTIMAL RELEASE STRATEGIES ........................ 96 Methods ................................ ................................ ................................ .................. 99 R esults ................................ ................................ ................................ .................. 101 Discussion ................................ ................................ ................................ ............ 104 5 POST STOCKING ASSESSMENT: EVALUATING FLORIDA LARGEMOUTH BASS SIZE DEPEDENTS ON ELECTROFISHING EFFECTIV ENESS IN PONDS. ................................ ................................ ................................ ................ 118 Methods ................................ ................................ ................................ ................ 121 Results ................................ ................................ ................................ .................. 123 Discussion ................................ ................................ ................................ ............ 126 6 CONCLUSIONS ................................ ................................ ................................ ... 140 Utilization of Hatchery Reared Bass ................................ ................................ ..... 140 Hatchery Reared B ass Angling Vulnerability ................................ ........................ 142 Aquaculture Based Fisheries Management ................................ .......................... 142 Post Stock Assessment ................................ ................................ ........................ 143 Future Research ................................ ................................ ................................ ... 144 Best Hatchery Product ................................ ................................ ................... 144 Post Stocking Evaluation ................................ ................................ ................ 145 Genetic linked Growth Implications ................................ .............................. 146 APPENDIX: GROWTH AND PERFORMANCE GENERAL LINEAR MIXED MODEL RESULTS ................................ ................................ ................................ ............. 147 REFERENCE LIST ................................ ................................ ................................ ...... 150 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 170
7 LIST OF TABLES Table page 2 1 Mean () standard deviation and range of morning dissolved oxygen (mg/L), pH, and total ammonia nitrogen (mg/l) in each of the six pond replicates stocked with 600 Florida bass in March 2013 and harvest March 2014. ............ 58 2 2 Percent survival calculated from initial numbers (N = 200) of Hatchery Standard (HS), Hatchery Grade out (HG), and Hatchery Forage (HF) cohort Florida bass and total survival per pond (N = 600) at 2, 6, and 12 month .......... 59 2 3 Instantaneous mortality of Hatchery Standard (HS), Hatchery Grade out (HG), and Hatchery Forage (HF) Florida bass between stocking 2 months, 2 6 months, and 6 12 months post stock ce nsus in six replicate ponds ....... 60 2 4 Cumulative mean (standard deviation) population lengths (millimeters) and weights (grams), mean population growth, and growth rate per day from initial stock date (N = 300 per cohort) collected from n = 50 ............................... 61 2 5 Mean population condition factors (K) for Hatchery Standard (HS), Hatchery Grade out (HG), and Hatchery Forage (HF) cohort Florida bass at initial stocking, 2, 6, and12 month post stock census from six replicate ponds ........... 62 3 1 Initial numbers of Hatchery Forage, Hatchery Standard, and Hatchery Grade out bass stocked in three 0.10 h a ponds, mean length and treatment mean (SD) in mm, total cumulative time fished (min), ................................ ................ 88 3 2 Model selection using Akaike information criterion (AIC) for varying catchability models for thre e bass types. ................................ ............................ 89 3 3 Cumulative fishing time (min) required to capture (not counting re captures) 50% of each treatment per pond and treatment mean (SD) indicated vulnerability to first time c apture between treatments. ................................ ........ 90 4 1 Initial number stocked, individual mean length (mm) and weight (g) from pond reared populations of Florida bass fingerlings, and the total weight stocked (kg) at 30, 40, 60, and 90 mm size classes ................................ ........ 110 4 2 Total pond harvest weight (kg), total number of bass harvested, individual average length (mm SD) and weight (g SD) at harvest, survival, and final remaining density (bass/m 2 ) ................................ ................................ ............. 111 4 3 Condition factors (K), n = 100, for initial pond reared Florida bass populations produced for stocking 30, 40, 60, and 90 mm size classes at 1,4 ,7, an d 10 bass/m 2 densities ................................ ................................ ............................. 112
8 5 1 Individual pond characterisitcs including an estimated pond bottom coverage by submerged multicellual algae and macrophytes in six relicate hatchery ponds located in Webster, Florida ................................ ................................ .... 134 5 2 Number of bass collected per pond per single five minute electrofishing sample event, total number of bass harvested per pond following draining, percent (%) of the actual population electrofished ................................ ............ 135 A 1 General linear mixed model ANOVA analysis depicting F Stat, P value, R 2 value) between three Florida bass cohort s (Hatchery Standard, Grade out, and Forage) length and weight. ........ 148 A 2 General linear mixed model ANOVA analysis comparing F Stat, P value, R 2 value) be tween three Florida bass cohorts (Hatchery Standard, Grade out, and Forage) cumulative population ... 149
9 LIST OF FIGURES Figure page 2 1 Morning oxyge n (mg/l) and temperature ( o C) data recorded from six replicate ponds in Webster, Florida. ................................ ................................ .................. 63 2 2 Mean surviv al of Florida bass over a one year period in six replicate hatchery ponds in Webster, FL.. ................................ ................................ ....................... 65 2 3 Instantaneous daily mortality estimate s for Florida bass co ha bituated in six hatchery ponds (0.24 0.28 ha) ................................ ................................ ......... 6 6 2 4 Instantaneous daily mortality e stimate comparison of Largemouth Bass co habituated in six hatchery ponds (0.24 0.28 ha) grouped by treatment. .......... 67 2 5 Length frequency distributions (total length, mm) of three cohorts of Florida bass census h arvested ................................ ................................ ....................... 68 2 6 Cumulative mean popu lation growth rate mm/day and g/day between initial sto cking ................................ ................................ ................................ .............. 70 2 7 Cumulative mean population growth in mm a nd g between initial stocki ng ........ 71 2 8 Photographical visual c omparisons of Florida bass harvested one year post stock from two of six r eplicate ponds ................................ ................................ 72 3 1 Comparis on of initial unfished and cumulative fished (caught hook and line) bass treatment populations by lengt h (mm). ................................ ....................... 91 3 2 Calculated catch rates per hour plotted by actual angling duration for each bass treatment. ................................ ................................ ................................ ... 93 3 3 Average catch ra tes per event plotted by angling duration for each bass treatment. ................................ ................................ ................................ ........... 94 3 4 Average catch per event (from the three replicates) and best performing AIC models. Model 1 (most parsimonious) repres ents constant catchability with .... 95 4 1 Total average population length and density differences between initial size (mm) at stocking density (m 2 ) and final harvest lengths and densities for Flo rida bass 30 days post stocked in 0.08ha ponds ................................ ......... 113 4 2 Results combining each size class by stocking density to compare final density after 30 days post stock. The independent variable was sto cking density (m 2 ) and the dependent variable was harvest density (m 2 ) .................. 114
10 4 3 Total final survival of four size classes of age 0 Florida bass s tocked in 0.08 ha hatc hery ponds in central Florida and harvested 30 days post stock .......... 115 4 4 Differences between initial and final mean population lengths represented average somatic growth in mm 30 days post stock for age 0 Florida bass each stocked at four inc reasing densities ................................ ......................... 116 4 5 Average individual final lengths at harvest of Florida bass per size class showing dens ity dependent growth. Size increases were reduced as stocking density and initial stock length increased. ................................ .......... 117 5 1 Evaluates ability of boat electrofishing to effectively sample known stocked F lorida bass age 0 to age 1 populations (>105 and < 320 mm) ..................... 136 5 2 Least squares regression analysis of electrofishing catch per effort (bass/min) as a function of known bass densities (bass/ ha) from six repl icate ponds ................................ ................................ ................................ ................ 138 5 3 Least squares regression analysis of known bass densities as a function of electrofishing catch per effort. The line reflects the ability to predict bass density from catch per effort in an attempt to determine when post stock ........ 139
11 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy EVALUATING HATCHERY PRODUCED FLORIDA LARGEMOUTH BASS Micropterus floridanus FOR FISHERIES MANAGEMENT By Michael David Matthews May 2015 Chair: Kai Lorenzen Major: Fisheries and Aquatic Sciences Stocking programs are carried out for a variety of fisheries management and conservation objectives with varying expected outcomes. Typically such programs require hatchery production of large nu mbers of juv enile fish which must be able to perform in natural environments and become catchable in the fishery. They furthermore require assessment of size and density dependent effects on survival and growth following release in order to assess effective rearing st rategies and determine effective release protocols. My study addressed these issues for the Florida largemouth b ass Micropterus floridanus stocking program. My first objective evaluated the impact of different hatchery rearing methods on survival and grow th of fish released into simulated natural conditions at 2, 6, and 12 months post stocking. Results indicated an initial performance advantage of juveniles reared in ponds on natural forage over juveniles reared in indoor tanks on pelleted feed, but no pe rformance difference s among groups were apparent one year post stock. My second objective c ompared the catchability (vulnerability to angling) of the forage reared and the two pellet reared groups of bass >250mm Neither catch per angling hour nor c umulati ve angling time required to catch 50% of the treatment group
12 differed significantly among groups. These results indicate that the different production protocols employed in this study do not significantly influence angling vulnerability. My third objecti ve examined the impact of stocking size and density on survival and growth under conditions where natural recruitment of bass is absent. Results show that 1) s urvival d oes not clearly increase with size 2) survival and growth are moderately density depen dent, and 3) availability of forage fish becomes critical to survival after bass reach a sizes > 60 mm. Thus, s tocking effectiveness depends on more than just producing larger sized bass. My final objective evaluated the effectiveness of electrofishing for quantifying the abundance of juvenile largemouth bass, a method widely used to evaluate stocking success and improve release protocols. Vulnerability was found to increase steeply with size after fish reach a length of about 140 mm. Consequently, samples taken before the majority, not the average, of the age 0 bass reached 140 mm, resulted in poor estimates of abundance and survival.
13 CHAPTER 1 INTRODUCTION Hatchery programs are widely used in fisheries enhancement and restoration. Stock enhancement, is a well established, widely used management tool applied for the purpose of improving the quality of recreational fisheries. Higher levels of fishing effort can be sustained through enhancements where recruitment from wild and hatchery fish and the direct c apture of hatchery fish alleviate the effects of high fishing effort (Bell et al 2006). Consequently, in some fisheries, stock enhancement is used as a management tool to augment the productivity of healthy fish populations by increasing the density of a pre existing species or by introd ucing a new one (Boxrucker 1986; Churchill et al. 2002). Additionally, stock enhancement enables the possibility to manipulate population structure to maximize biomass production and/or the abundance of catchable sized fi sh (Lorenzen et al. 1997; 2012). Many differing hatchery typologies are used to justify production of many species of fish (Lorenzen et al. 2012) and can be used to increase catch rates, mitigate the effects of fishing, and rebuild depleted fisheries (Lor enzen et al. 2010). Despite the extensive use of stock enhancement and its potential to provide diverse, biological, ecological and socioeconomic benefits (Arbuckle 2000; Lorenzen 2005; Halverson 2008), the outcomes of stock enhancements have been wide ra nging and depending on the variable or variables considered there are few cases where stock enhancement is considered completely successful (Hilborn 1998; Smith et al 2002). Understanding the possible outcomes of enhancements must be evaluated on multipl e criteria and take into account multiple, and often, conflicting objectives.
14 Effective ness of hatchery programs in achieving their objectives is reliant on multiple factors specific to the desired outcome. M ass production of juveniles that are fit to su rvive, condition of natur al stocks and their environment, appropriate release strategies, fishing regulations, assessment of potential disp lacement of wild genetic traits, and defining safe and effective success criteria after considering these factors. C onsequently, hatchery programs need to address concerns such as domestication effects, ecological and genetic interactions between hatchery and wild fish, timi ng, size, and density of fish t o stock, and effects of stocking on fishing effort and catchabilit y. Domestication is thought to enable cultured fish to perform better under culture conditions through selective breeding and developmental responses obtained during exposure to hatchery env ironments Conve rsely, domesticated fish often perform poorly whe n released into natural environments (Lorenzen et al. 2012) Cultured fish can intentionally and unintentionally experience developmental, behavioral, and genetic manipulations as a result of the hatchery rearing process ( Fleming and Petersson 2001; Naish et al. 2007; Lorenze n et al. 2012). Domestication a ffects documented in cultured species (Gro ss 1998; Thorpe 2004) possibly a ffect morphological, physiological, behavioral, and genetic traits ( Harmon et al. 2000; Lorenzen et al. 2012) and are thought to be major contributing factors to a decline in fitness of cultured fish (Hilborn 1992; Hilborn and Eggers 2000) and may also affect their susceptibility to capture (Huntingford 2004). Domestication effects can be reduced but not completely eliminated by us ing wild broodstock allowed natural selection ( Hhn et al. 2014) and adopting husbandry practices such as habitat enrichment and life skills training.
15 Loss of genetic variability is an additional concern for conservation minded enhancement fisheries pro grams trying to protect the genetic integrity of endemic populations. Fisheries management agencies have begun to develop stocking programs that focus on maintaining or enhancing relative fitness characteristics to improve survival and recruitment by main taining genetic diversity of stocked populations ( Fries et al. 1996 ; Tringali and Bert 1998 ; Fleming and Peterss on 2001; Barthel et al. 2010 ; Austin et al. 2012 ) Heritable traits of high economic importance to fish culturists (growth rate, disease resistance, and food conversion efficiency) have often preceded ma intenance of natural genetic variability ( Tave 1993 ) The loss of genetic variability and decl ine of phenotypic and physiological traits in wild populations due to poor husbandry and replacement of wild alleles through immigration, reduced levels of genetic variance, and inbreeding depression as a direct result of errant stocking should be avoided (Tringali et al. 2007). The Florida Bass Hatchery Program Largemouth bass, Micropterus salmoides, is a highly prized inland game fish and is one of the most intensively managed species in North America (Fries et al. 2002). Florida is home to a unique sp ecies of largemouth bass, the Florida largemouth bass Micropterus floridanus (Bailey and Hubbs, 1949) Its physical appearance is indistinguishable from the northern counter part, but the Florida bass is notorious for its potential to rapidly reach trophy s ize. Florida bass are only native to the state of Florida and pure strains are only naturally found south of the Suwannee River (MacCrimmon and Robbins 1975 ; Barthel et al. 2010 ). Florida bass receive much attention because they are the most commonly targ eted freshwater sportfish in Florida, being targeted on 62% of the 29.73 million freshwater angling days in Florida (USFWS 2011).
16 Generally Florida bass are aggressive, opportunistic predators with a lifespan of ten years and become sexually mature at two years of age. Breeding season begins in the spring when water temperatures reach ~18C and continues for 2 3 months or in South Florida even longer (Rogers and Allen 2009). Males build n ests and attract females which are iteroparous fractional spawners and only release a portion of their eggs at a time. Once the eggs have hatched, the males will defend the fry from predators until the fry disperse from the nest, which is usually less than two weeks post hatch The Florida bass population is generally not considered to be threatened or overexploited by harvest Hoyer and Canfield (1996) reported exploitation levels that did not represent overfishing and did not alter the size distribution of the fi shery; however, smaller lakes in Florida could experience higher rates of exploitation. If the trend of voluntary catch and release continues, there do not appear to be risks of harvest overexploitation in the future ( Noble 2002 ; Allen et al. 2008; Myers e t al. 2008 ). Despite most bass populations in Florida not being at risk for overexploitation by harvest, diminished habitat quality and quantity in lakes is believed to weaken compensatory processes and reduce recruitment to the fishery. Measured and publ icly perceived declines in abundance and catch rates have promoted fisheries biologists to conduct d rawdowns, bottom sculpting, and re vegetati on projects for improving or re generating bass fisheries. bodies of water, which are harder an d more costly to drawdown then reservoirs, have become impractical to utilize drawdowns due to cost, usage group confrontations, and legal issues. Social and economic pressures on fisheries managers to maintain
17 acceptable catch rates under increased fishi ng pressures and with the loss of based stocking projects. Unfortunately, fisheries managers are faced with the dilemma of what needs to be done and what can actually be done in the a ttempt to manage Florida bass populations. Often the basis of a declined bass population is rooted in angler perceptions and not rigorous science. Since the 1930s, many states in the southeastern United States have stocked Florida bass in an effort to gen erate or maintain quality fishing lakes and increase license sales (Buckmeier et al. 2003). Stocking may be used to reduce the variability in naturally fluctuating populations to help stabilize catch rates (van Poorten et al. 2011). This stocking strategy has been used by fisheries managers in attempts to maintain bass populations and increase angler satisfaction. Before the only small fingerling bass were typically stocked in Florida. Many of these stockings took place in newly renovated water b odies, overexploited urban lakes, or after devastating fish kills caused by weather related disasters. Perceived p oor natural recruitment in degraded lakes, with pre existing bass populations, led to the development of an advanced sized fingerling stockin g program. Considerably less than optimal stocking conditions were observed in these systems but habitat restoration projects remain cost prohibitive. Researchers proposed that stocking larger, pisc i vor u s bass, would increase survival and by pass the fo rage bottleneck hypothesized as perpetrator for the poor recruitment (Loska 1982; Wahl et al. 1995; Buynak and Mitchell 1999; Lasenby and Kerr 2000). Conversely, in lakes with no established bass
18 populations, the introduction of fry and/or fingerlings rem ains typical (Smith and Reeves 1986). In Florida, i nitial poor survival rates of stock bass were attributed to improper nutrition which was alleviate d by the creation of the Richloa m Bass Diet (Porak et al 2002 ; Cardeilhac et al. 2004; Cardeilhac 2011 ) Since 2007, more than 900,000 pellet reared advanced fingerling s have been stocked into Florida waters. Advanced fingerling s tocking results thu s far have been mixed considering differing perceptions of success (e.g. contribution and survivability outc omes ) leading to concerns about advanced hatchery reared fingerling effectiveness The combination of conserving this unique endemic species of black bass ( Phili pp et al. 1981 ; Philipp et al. 1983 ) and maintaining the quality of the recreational fishery requires a combination of management measures including defendable, fair regulations, preserving habitat from further decline, and optimal hatchery production and release practices. Statewide bag and length limits defend against overexploitation. Controlled harvest is potentially useful in promoting population growth and preventing slower growing over populated systems. Unfortunately, inconsistent or minimal harvest reduces some of the potential benefits of harvest regulations ultimately rendering this management typology less effective Habitat degradation from natural and anthropogenic origin will likely nev er be restored to observed conditions in the distant past, but actions implemented in an effort to reduce future declines have been This plan is an integrative bass populations and habitats. Unfortunately, fisheries managers are not a fforded final control over Florida waters and
19 differing objectives of user groups can reduce habitat or restrict restoration in favor of bass populations. Finally, aquaculture bas ed management projects are basically the utilization and assessment of stocking projects are hindered by a variety of variables including, but not limited to, unconfir med causes of bass population declines confidence in pre stocked natural and stocked fish assessments, defined success criteria, when to stock, and ability of multiple types of hatchery products to recruit to the fishery. Culture practices for black basse s vary depending on required amounts and individual culture facility resources. Generally bass are stocked as fry, fingerling, advanced fingerling, or as sub adults. Due to the cannibalistic nature of largemouth bass, they are typically stocked before th e sub adult phase. Stocking bass at smaller sizes also allows for greater product availability and decreased production costs. Fry are stocked 6 to 8 days from hatch. The <10 mm fry are very susceptible to predation; however, this may b e acceptable from a stocking standpoint as the production of millions fry is attainable. Successful stockings of fry in new water bodies lacking pre existing fish populations are possible. Bass are more commonly stocked as fingerlings ranging 28 60 mm in total length. T ypical fingering stocking rates in the southeastern United States are 250 per ha; however, the stocking densities of these 30 day old bass vary from state to state. Stocking bass fingerlings can be successful in highly vegetated habitats with high levels of forage. Stocking bass fry and fingerling s are proven methods to promote adult bass populations in new systems, but are perceived less suitable to stock in pre existing predator populations. Initial predation of stocked Florida
20 bass (30 to 46 mm TL) wa s as high as 27.5% within 12 hours of stocking (Buckmeier et al 2005). Advanced fingerling bass protocols were developed to stock lakes with pre existing predator populations or surpass suspected recruitment bottlenecks specifically impacting natural fry progression to fingerling (Porak et al. 2011) Researchers speculated that stocking degraded systems with larger bass cou ld have a potential greater impact for stock enhancement (Porak et al. 2002) The spatial costs associated with live reared advanced fingerling bass production in ponds increases 5 to 20 times compared to more controlled intensive pellet reared advanced fingerling production. Rearing techniques incorporating pelleted diets in indoo r raceways reduced spatial costs incurred from pond rea ring (Diana and Wahl 2009). The proposed increase in survival rates of the larger stocked bass may compensate for the additional costs. In Florida, advanced fingerling stocking rates range from 15 and 250 bass/ha while literature reported bass stocking r ates of 8 to 448 bass/ ha (Heitman et al. 2006). The stocking of advanced size largemouth bass demonstrated positive increases in population and creel catch/ha rates, but the effects were short lived (Buynak et al. 1999; Hartman and Janney 2001). Examples of advanced fingerling stocked in Florida convey mixed results surrounding varying metrics of success and based on multiple production protocols. Mesing et al. (2008) reported 20% live reared bass contribution to a fishing tournament after four concurren t years of stocking 65 to 90 mm bass on Lake Talquin, Florida. Due to spatial limitations for the production of live reared bass, research began on large scale bass production using artificial diets. Pouder et al. (2010) found that the inability of pelle t reared bass to quickly transition to
21 natural prey possibly increased mortality of stocked fish seven days post stock but did not compare to live reared hatchery bass mortality over the same time frame In many situations it appears as though hatchery re ared fish experience higher mortality than expected compared to fish of wild origin (Lorenzen 1996; 2008; Fritts et al. 2007; Lorenzen et al. 2012). The reasons for the reduced survival in the wild of hatchery raised fish are not fully understood; however, relaxed culture environments and high rearing densities of hatchery reared fish alter multiple morphological, physiolog ical, and behavioral traits are likely to be major c ontributing factors (Huntingford 2004). Studies demonstrating reduced bass survival may also be attributed to ineffective juv enile sample timing and methods. The effects of culture induced domestication on post release fitness comparing hatchery reared types and hatchery reared to wild bass need rigorous exa mination to better understand and to effectively utilize hatchery reared bass for fisheries management purposes. The demand for stocking larger numbers of advanced fingerling bass over fry or fingerling necessitated the utilization of artificial feeds and more intensive spawning proto cols ( Brauhn et al. 1972; Matthews and Stout 2013). The controlled rearing environments increased production yields however may unintentionally intensify domestication concerns that compromise post release performance of hatchery bass and suggested that the poor survival r esulted from something more complex. Evidence of increased mortality has been recorded after one month post stocking intensively pellet reared bass compared to live reared bass (Porak et al. 2011). Conditioning to forag e and/or predators revealed short t erm post stocking survival and foraging ability of pellet reared hatchery bass significantly improved (Pouder et al. 2010; Olsen et al.
22 2012; Rachels et al. 2012). Incorporating these results remains largely untested in natural simulati ons over longer per iods (> 1 year ) of time. One study showed age 1 post stock pellet reared survival estimates from natural lakes ranged from 0 to 8%, but the results are debated concerning sampling efficiency, lack of comparative live reared data, and undeclared values of success (FWC 2013). These studies showed diminished foraging and predator avoidance issues culture conditions initially create, but direct comparisons of live and pellet reared advanced fingerling through recruitment age, including angling vulnerability, require investigation. Additional important factors concerning bass stocking success are pre ex isting natural bass populations includes; potential recruitment rates, size and density dependent processes, identifying the actual recruitment limiting fact or(s), acc urate post stock assessment, timing and forage base. Horne and Lochmann (2010) found no significant effect on mortality and growth of wild pre existing bass populations due to stocking advanced sized bass at low densiti es. Stocking larger bass (live or pellet reared) may increase chances of hatchery reared bass survival compared to a smaller sized stocked bass, but should not be expected elevate lake densities already near carrying capacity. Many factors contribute to recruitment and formation of each year limiting factor before stocking The initial unknown cause of the reduced natural populations (if any, could currently be at carrying capacity) could h ave stemmed from multiple environmental issues that stocking bass in any form would be unable to compensate. Determining lake characteristics best suited for bass stocking for a specific size and rearing technique would optimize hatchery resources (Hoxmei er and
23 Wahl 2002). It is crucial to understand how hatchery metrics and post stock analysis relates to the perceived success of each stocking event. Accurate and reliable assessments of age 0 fish are difficult to collect but important for management de cisions specifically considering stocking and post stock performance. Modeling fish densities from catch per unit effort data has shown to be conditionally effective concerning larger sub adult and adult fish (Coble 1992; Hall 1986), but catchability is v ariable concerning temporal and environmental factors (Bayley and Austen 2002 ; Schoenebeck and Hansen 2005 ) and thus weakens the density depende nt catchability relationship (H angsleben et al. 2013) Bass stocking programs equally try and monitor stocked p opulations for evaluation and contribution of stocked bass to the age 1 year class (Diana and Wahl 2009; Buynak and Mitchell 1999), but juveniles are less susceptible to boat electrofishing capture and other capture methods are less practical (Johnson and Nielsen 1996; Hayes 1996; Hubert 1996; Jackson and Noble 1995). Angling vulnerability of different rearing techniques is a relativity un assessed outcome of bass stocking that could potentially have implications for future production and stock enhanceme nt decisions. If the catchability of live reared bass significantly differs from pellet reared bass, stocking recommendations for each group would need re assessment. Catchability or vulnerability to angling is generally thought to be a product of an ind ( Bryan and Larkin 1972 ) Though a number of early evaluations report a difference in catchability between individual bass an d fished and unfished populations ( Anderson and Heman 1969 ; Hackney and Linkous 1978 ) researchers only recently investigated vulnerability to angling as a heritable trait.
24 Garrett (2002 ) tested selective breeding in wi ld bass to determine if angling vulnerability is a predictable, herit able component. The second generation bass bred for high vulnerability were likely to be caught multiple times compared to the un vulnerable bred ility was heritable. Philipp et al. (2009 ) showed after three generations (F 1, F 2, and F 3 ) of hatchery stocked high and low vulnerability bred largemouth bass, catchability comprised a genetic heritability of 0.146 (r 2 = 0.995) for F 3 offspring. Indicating that vulnerability of largemou th bass to angling was a heritable trait. Released cultured fish have been shown to be more susceptible to fishing gear than their wild conspecifics in some studies (Mezzera and Largiader 2001). Specifically of interest for the scope of this manuscript i s the susceptibility of hatchery reared Florida bass > 250 mm to angling Angling vulnerabilit y in wild populations differ among species and strains and is not limited to only Largemouth bass (Rieger et al. 1978; Kleinsasser et al. 1990; Askey et al. 2006 ), but catchability of differing h atchery production techniques remains unknown. The complexity surrounding enhancement projects and developing successful stocking criteria shows the need for integrating understanding of both aquaculture and fisheries disc iplines for future enhancement projects (Lorenzen 2014). Bass size needs consideration as larger bass require more hatchery resources and delays stocking Live rearing adequate quantities of bass to larger sizes can limit hatchery resources and may requi re alternate production protocols (pellet rearing) to achieve large requests, providing the resulting product of both rearing techniques promote approximately equal age 1 survi val and angling vulnerability. Stocking larger sized fish potentially increases survival as they are less vulnerable to predation and have greater prey item availability
25 (Diana and Wahl 2009; Hoxmeier et al. 2006; Porak et al. 2002; Wahl et al. 1995, Wahl and Stein 1989). Trade offs for producing larger fish in hatcheries delay stoc king times and can require stocking larger fish on top of similar sized naturally produced age 0 fish (Diana and Wahl 2009). This negates any competitive advantage for the stocked fish and possibly increases density dependent growth influences on recruitm ent to the age 1 year class (Hazlerigg et al. 2012). Finally, c urrent Florida based enhancement programs attempt to maintain zones or management units (Porak et al. 20 15 ). Hatchery broodstock is comprised of a large number of wild caught pure Florida bass Research confirmed broodstock numbers were acceptable and loss of genetic contribution was minimal (Austin et al. 2012). Researchers are cautioned to maintain larg e broodstock populations to reduce the risk of unintentionally decreasing genetic diversity possibly declining stocking effectiveness bef ore the fish leave the hatchery (Tave 1993; Lorenzen 2014) Research Questions The above review of the Florida bass fis heries program identified several areas and issues that warrant further research. Of these, I chose to address the following in this dissertation: (1) How do alternative hatchery production protocols (intensive pellet based rearing with grading vs. extensive f orage based rearing in ponds) affect post release survival and growth? This question is addressed in Chapter 2 of this dissertation. Fish raised using alternative protocols are tested under identical, simulated natural conditions and allowed for actual sur vival data collection and growth and performance
26 evaluation at three selected points through age 1 revealing the effects of live and pellet reared production for comparison. (2) How do alternative hatchery production protocols (intensive pellet based rearing w ith grading vs. extensive forage based rearing in ponds) affect angling catchability? This question is addressed in Chapter 3 of this dissertation. Fish raised using alternative protocols are subjected to angling after they surpassed 250 mm TL in order to evaluate catchability differences between hatchery reared bass recruited to fisheries populations. (3) How do stocking size and density affect post release survival and growth of Florida bass stocked for population recovery in systems where natural recruitmen t is absent? This question is addressed in Chapter 4 of this dissertation. Fish are stocked at different sizes and densities to assess size and density dependent survival and growth. (4) How and when can stock outcomes be reliably assessed with electrofishing surveys? This question is addressed in Chapter 5 of this dissertation. Electrofishing samples were compared to the known census data, collected in Chapter 2, to evaluate suitable recruitment to the sampling gear for accurate post stock assessments and at tempted to employ catch per effort as a means of estimating standing populations.
27 My combined efforts contribute additional information for continued stock enhancement endeavors and foster the need for continued integration of aquaculture based management as a valuable tool for fisheries managers.
28 CHAPTER 2 COMPARISON OF INTENSIVE PELLET AND LIVE REARING ON FIRST YEAR POST RELEASE PERFORMANCE OF FLORIDA LARGEMOUTH BASS Cultured fish experience developmental, behavioral, and genetic changes as a result of the hatchery rearing process (Lorenzen et al. 2012) compared to fish produced naturally in the wild Domestication effects documented in cultured species (Gross 1998 ; Thorpe 2004 ) influence morphological, physiological, behavioral, and gen etic traits (Lorenzen et al. 2012) and are thought to be a major contributing factor to a decline in fitnes s of cultured fish (Huntingford 2004). Lack of predator avoidance (Berejikian 1995) and foraging ability (Hughes et al. 1992) in stocked hatchery b ass has been documented for other predatory species (Brown and Laland 2001). Fish normally acquire predator recognition skills in the wild by the presence of chemical indicators released by conspecifics stimulated by active predator foraging (Olson et al. 2012). Different rearing methods are hypothesized to affect domestication processes differently. Rearing under more natural conditions (e.g. in ponds on natural forage) is often assumed to result in fish that are more wild like than those reared in indoo r tanks on pelleted feed. Also, certain practices such as enrichment of tanks with structure or predator avoidance training may be implemented to enhance life skills in hatchery fish (Lorenzen et al. 2012). This study focuses on the possible survival and performance differences between advanced hatchery reared bass resulting from pellet and zooplankton (live) rearing techniques Largemouth bass Micropterus salmoides and Florida Largemouth bass Micropterus floridanus fry and fingerling production is typi cally completed in outdoor ponds. Fry are collected from brood ponds and stocked into zooplankton rich, fertilized
29 ponds for fingerling production ( Piper et al. 1986 ; Simco et al. 1986 ) Typical yields h arvested from 0.4 ha ponds, after a 25 to 35 d grow out period produce 48,000 (60% survival) 25 40 mm bass fingerlings (Matthews and Stout 2013). Pond production of advanced fingerlings on natural forage requires greater hatchery spatial resources with low er final harvest returns; making large scale pond p roduction impractical at many hatcheries. Incorporating an artificial pelleted feed increases yield and reduces hatchery expense (Sloane and Lovshin 1995). A live reared advanced fingerling Florida bass stocking program was developed by Florida Fish an d Wildlife Conservation Commissio n (FWC) staff at the Florida Black Bass Conservation Center (FBCC). Production returns at the FBCC after stocking 10,000 to 12, 000 fingerling bass (25 35 mm) in 0.4 ha ponds averaged 5,000 advanced fingerling bass (60 to 9 5 mm) reared on live forage ( unpublished data). Small total product ion amounts and other sp ecies production demands for hatchery space limit advanced forage reared Florida bass production Demands for greater numbers of advanced fingerling bass required intensification of production through new protocols and techniques including; (1) changing spawnin g protocols (Matthews and Stout 2013); (2) intensive husbandry practices including incubation protocols ( Bebak et al. 2009; Matthews et al. 2012); (3) large scale feed training ; and (4) adequate nutrition ( Cardeilhac 2011; Csargo et al 2013 ) for pellet rearing in raceways. These advances culminated in intensive Florida bass production capabilities that ranged from 80,000 to 120,000 advanced fingerling (85 120 mm) bass per 24 m concrete raceway (45,400 L ) in 150 days from hatch. Pond and raceway reared bass are exposed to cohort cannibalism during grow out. This increases mortality and requires grading bass from
30 the raceways to remove the larger, more aggressive cannibalistic i ndividuals commonly exclusively a result of the hatchery rearing environment or a phenotypic difference in growth potential that may or may not persist after being stocked into the wild. It is also unclear how grade out bass and the remaining pellet reared bass survive in the wild compared to forage reared bass. Multiple studies concerning post stock survival of hatchery reared largemouth bass found poor initial post st ock foraging skills (Larscheid et al. 1999; Pouder 2010; Rachels et al. 2012), possible metabolic differences (Garlock et al. 2014), reduced anti predatory and sociability behaviors (Kiefer and Colgan 1992; Johnsson et al. 2006; Monk 2013 ), altered jaw mor phology (Wintzer and Motta 2005) and increased movement into unprotected ope n water areas (Thompson 2012 ). Recognizing and accounting for these o bserved differences may increase post stocking success. Evidence of domestication effects have been recorded after one month post stocking bass in controlled and natural settings. All h atchery rearing protocols may affect post release performance. Pond and tank studie s conditioning hatchery bass to forage and predators showed initial increases in head to h ead f oraging ability trials compared to un conditioned hatchery bass ( Porak et al. 2011 ) Both showed greater predator avoidance skills when placed in equal numbers in tanks containing refuge and large predators Incorporating these results remains largely unt ested in more natural s it uations over long periods (6 to 12 months) of time Current stocking protocols followed by the FWC include stocking lakes with advanced sized 100 mm fingerling bass into recruitment limited and habitat degraded
31 systems. Stockin g evaluation and the effects of stocking hatchery fish on the pre existing wild bass population is important to refine culture and stocking methods to optimize stocking success (Horne and Lochmann 2010). Managers need to be cautious when comparing surviva l results because initial study criteria, rearing techniques, and stocking rates are seldom identical. Direct comparisons of hatchery reared bass from post stocking results from different studies can be difficult because of the broad variability in initia l fish size and stocking rate/ha (Buynak and Mitchell 1999; Diana and Wahl 2009), rearing technique (Buckmeier and Betsill 2002; Heidinger and Brooks 2002; Pouder et al. 2010), time of stocking, (Garvey and Stein 1998; Neal et al. 2002; Mesing et al.2008), sampling method (Jackson and Noble 1995; Ozen and Noble 2005) and reason stocked. Comparing survival results for fish originating from similar hatchery rearing and stocking protocols will allow more meaningful analysis and possibly optimize future stocki ng successes. Hatchery related m ortality effects from pellet rearing largemouth bass after being stocked in to lakes, compared to live reared hatchery bass mortality may n ot be significantly different as a result from the specified rearing protocol M ore work is needed to assess whether pellet reared bass have different survival than live reared hatchery bass. All culture environments modify behavior traits affecting post stock fitness (Lorenzen et al. 2012), and decrease survival compared to wild ori gin fish (Lorenzen 1996). Austin et al. (2012) showed the greatest decline in allelic diversity occurred during spawning or in the initial fry pond rearing phase compared to feed tra ining and subsequent grow out phase. This possibly implies equivalent ha tchery related domestication effects on all advanced fingerling protocols. Diana and Wahl
32 (2009) reported no statistical difference in long term, post stocking growth or survival between bass reared using different culture techniques to advanced sizes; so me bass were fed fathead minnows and another group was fed pelleted feeds. Unfortunately the researchers could not compare rearing practices as the two rearing techniques were combined to compare the effects of bass size at initial stocking and not l ive v s. pellet reared long term post stock survival. The p urpose of this research is to ascertain long term survival of two groups of advanced pellet reared Florida bass and a designated live reared hatchery group ( zooplankton reared) in outdoor research ponds one year post stock to assess and compare performance abilities between the differing techniques Utilizing replicated hatchery ponds removes the variability typically associated with sampling gear and allowed comparison of pellet reared and live prey re ared bass solely based on biological criteria. Methods We compared survival and growth of three groups of bass at two, six, and twelve months post stocked into research ponds. Two treatments were intensively reared in raceways on pelleted f eed and ar e similar based on rearing protocols The difference being that one of the two treatments originated from grading the more aggressive, faster growing subset of pellet reared bass typically removed from each raceway reared population to reduce feeding aggr ession induced disease outbreaks and cannibalism. The third cohort remained in ponds and reared on natural forage represented the closest wild or un domesticated produced hatchery reared bass. To simulate standard advanced fingerling production protocols, initial mean stocking lengths of 100 mm were sought for all groups but typically are not obtainable in live rearing due to lack of sustainable forage items Same aged fish from the s ame parents were used to
33 minimize potent i al size variation Six ponds, ranging from 0.24 to 0.28 ha, located at the Florida Bass Conservation Commission (FBCC) in Webster, FL were co habited with equal numbers (N = 200) of three groups of hatchery reared Florida bass ; (1) pellet ) ( 2) a larger pellet reared faster growing, possibly genetically based in combination with cannibalism, group graded from Hatchery and Production P rotocols The ba ss utilized for this study originated from two indoor 24 m concrete spawning raceways stocked accordingly following out of season Florida bass production protocols (Matthews and Stout 2013). A total of 29 spawns were collected October 18 th 20 th and combined in a single 9.2 m hatching raceway. The fry were harvested 5 7 d post hatch and re stocked into two 0.40 ha fertilized earthen ponds at 197,600 fry/ha. Initial pond fertilization and su pplemental fertilization procedures followed standard hatchery practices (Coyle et al. 2012; Ludwig 2012). Both ponds were harvested 35 d post stock and transported to two indoor 9.2 m raceways for feed training (Matthews 2011, unpublished feed training p rotocol ). The approximately 40 d old, 0.25 g (28 mm) fingerlings acclimated to their new raceway environment for 24 h ou r s prior to the introduction of artificial food. Prior to feed training, 6,000 fingerlings were removed from each raceway and stocked into separate 0.25 ha earthen ponds. These bass represent the Hatchery Forage or zooplankton reared bass and considered nearest to truly wild produced bass hatchery reared conditions allow. The ponds were stocked on November 30 2012 and harvested 114 d later on March 23, 2013 Both ponds were fertilized to promote strong
34 zooplankton communities and supplemented with koi Cyprinus carpio fry four times during the winter months (124,000 fry/ha) to promote growth and create a prey rich environment. The mea n weight, length, and s urvival of the Hatchery Forage treatment ; 7 g, 88 mm (60 to 105 mm range), and 51%, respectively, provided the 1,200 Hatchery Forage bass required for the study. The harvested bass were placed indoors in a 9.2 m raceway and held les s than 12 h before stocked in the six study ponds. The Hatchery Standard and Grade out cohorts were produced from the remaining 30,000+ bass. Both 9.2 m raceways were combined to a single 24 m concrete raceway after feed training was completed and the ba ss averaged approximately 50 mm in total length (TL) Standard hatchery protocol requires the removal of the larger more aggressive bass as many as three times during production. The Hatchery Grade out cohort was attained from a single first grading of t he ent ire population on March 1 The Hatchery Grade out treatment allowed examination of survival and the persistence of the significantly elevated growth rates displayed by this second pellet reared group. The Hatchery Grade out bass were placed in a 9. 2 m raceway and t he 1,230 Hatchery Grade outs averaged 117 m m (95 to 151 mm range) and 21 g at stocking. The final cohort or Hatchery Standard bass were acquired from the remaining bass in the 24 m raceway Approximately 2,000 randomly selected bass were reassigned to a 9.2 m raceway. Mean weight, length and final total survival; 12.7 g, 100.5 mm (87 to 139 mm range), 70% (accounts for grade out removal) provide a true representation of pellet reared hatchery bass produced and stocked from the FBCC.
35 Fis h Treatment and Pond P reparation Each of the three bass treatments were harvested, enumerated, and stocked into the six research ponds on March 23. The harvest and re stock of these bass simulated typical harvest and transport procedures and completed ex peditiously to minimize domestication effects. Six, 284 L plastic transport tanks (one tank per pond replicate) supplied with pure oxygen were used for transport. A 0.5% salt solution was mixed in each tank to minimize handling stress. Each transport ta nk received 200 bass from each cohort. The bass were hand counted in 50 fish allotments and randomly (random number generator 1 6, Microsoft Excel 2010) assigned to a tank. Initial length and weight measurements from 50 bass per cohort stocked into each of the six transport tanks were collected for comparison. Measurements totaled 300 per cohort and 900 of the 3,600 bass were sampled prior to stocking. M easured fish were sedated with t rica ine m ethanesulfonate (Tricaine S, Western Chemical, Inc., Ferndal e, Washington). The remaining unmeasured 2,700 bass were sedated for handling and consistency. The pellet reared bass treatments were distinguishable from each other by the use of coded wire tags (CWT) inserted into the right cheek of the Hatchery Stan dard bass and the left cheek of the Hatchery Grade out bass. Tagging occurred 14 d prior to pond stocking. The bass were tagged using a Mark IV tagging machine (Northwest Marine Technology Inc. Shaw Island, Washington) and protocols mimicked methods desc ribed by Heidinger and Cook (1988). Both cohorts were tagged 8 d post stock into the 9.2 m raceways as not to compound stress factors. The Hatchery Forage treatment remained unmarked in an effort to minimize any domestication effects incurred during the tagging process. Tag retention and tagging mortality after 24 h was 100% and < 2% for both Hatchery Standard and Hatchery Grade out treatments. Tag retention 14 d
36 later on March 23, 2013 revealed 100% tag retention in Hatchery Grade out bass and 98% in Ha tchery Standard bass. Since every bass in each of the three cohorts were hand counted, the Hatchery Standard and Hatchery Grade out bass were tag checked to assure 100% marking of the two tagged populations at the beginning of the experiment. Untagged pe llet reared bass were discarded. The untagged Hatchery Forage cohort was similarly hand counted for handling consistency and assured exact numbers stocked into each pond Tagging and census harvest (c omplete pond draining to a concrete catch basin in the bottom of the pond ) of ponds allowed us to compare true survival between the three stocked cohorts, data previously unobtainable from stocked l akes. Data collected represented performance of the three cohorts and may provide information useful for future stocking decisions. Eastern Mosquito fish Gambusia holbrooki were supplied twice daily at a ratio of 4:1 mosqui to fish to Florida bass per day for eight days. Foraging skills and fish behavior were monitored prior to their release into research ponds. The six research ponds were filled with aged well water and fertilized for zooplankton production (Coyle et al. 2012; Ludwig 2012) six weeks before stocking the bass. Additionally, each pond received four large brush piles for structure, adult bluegill L epomis macrochirus and adult bass to create a more natural lake environment. Adult bluegill were stocked at 53 to 61 pair/ha for forage production a month prior to stocking the bass treatments. Bluegill sex ratios were skewed toward females as males wil l spawn with multiple females and in attempt to mitigate suspected loss of females from predation prior to spawning. To avoid possible predation and excessive loss of bluegill broodstock we stocked large males (175 250 mm) and females (150 to 225 mm).
37 Tra ditionally, bluegill brooders are stocked at a greater density for fry production (Dupree and Hunter 1984), but equal or greater fingerling production was reported at lower pair/ha densities (Simco et al. 19 86; Matthews 2000 ). Adult bass (330 to 482 mm) w ere stocked at 13/ha to serve as predators Hoyer and Canfield (1996) reported adult bass densities averaged 18/ha (>250mm) across 56 Florida lakes. We chose a lower adult bass density to simulate a management scenario suitable for stocking advanced fing erlings. Pond Sampling Each of the six research ponds wer e completely stocked in March 2013. The entire population of each pond was censuse d at two months (May), six months (September), and at 12 months (March 2014 ). For this purpose, each pond were com pletely drained to a 2,275 L in sampling period. Draining occurred over night to reduce concentration induced predation and allowed handling to occur during cooler morning hours. The pond bottoms were survey ed by foot to collect any trapped fish that did not make it to the kettle and to note any mortality due to draining the pond. Each kettle was split into three sections using 7 mm mesh aluminum screens. All fish were seined into one section for analysis. Adult bass and brood bluegill were hand counted at each sampling No predator bass were lost and brood bluegill numbers remained adequate one year interval. Forage amounts were observed for visual comparison, but total forage weigh t and size distributions were only collected upon the final 12 month harvest. Each bass was checked for microwire tags with a CWT reader and hand counted. Length (mm) and weight (g) measurements were recorded for the first 50 fish from each cohort. Pure oxyg en was supplied to the kettle and MS 222 (25
38 mg/l) kept the fish calm during handling. A 10x10 ft canopy p rovided shade for the kettle which prevented large water temperature increases during census. Pond bottom plant and algae coverage was visually esti mated at each harvest date for subsequent management treatment decisions. Percent vegetation bottom coverage was estimated visually. Plant coverage assessments (visual estimates) in percent bottom coverage were used for pond management decisions, but were not used for direct analysis in this study. The ponds were immedia tely refilled after sampling and required 12 to 15 hours to complete ly refill M ortality incidents were recorded if observed for three days post refilling. Water quality parameters inclu ding oxygen, pH, temperature, alkalinity, and total ammonia nitrogen levels were monitored as needed. This data was utilized for managing the study ponds (e.g., aquatic plant treatment) and help prevent mortalities of fish (e.g., aeration of a pond with l ow oxygen). Morning daily temperature ( o C) and dissolved oxygen (mg/L) levels were shown in Figure 2 1. Mean, standard deviation (SD), and r ecorded r anges of morning dissolved oxygen, pH and total ammonia nitrogen data are reported in Table 2 1 Dat a A nalysis Unistat version 6.0, UNISTAT Ltd. and Microsoft Excel 2010, Microsoft Corporation statistical software programs generated all analysis, figures, and tables. General Linear Mixed Model (GL M M) tests paired with Tukey Honestly Significant Dif ference ( HSD ) examined differences between and within cohort survival as well as determined significant distinction in mean lengths (mm), weights (g), growth rates (mm/d and g/d), and condition factors (K) (Blackwell et al. 2000) between cohorts from initi al stocking to each sampling point. Mortality rates compared between s ampling
39 points also utilized GL M M tests paired with Tukey HSD. A randomized complete block pond effects across the six replicates. A significance level of P = 0.05 was used in all statistical tests. The sample size of n = 50 per cohort per pond adequately met normality assumptions, Shapiro Wilk test probability > 0.2. Histograms set at 10 mm size groups were combined cohort data from all six ponds (n = 300) for comparative observation of each cohort from initial stocking to harvest at one year. Length and weight of a ll remaining bass collected at one year were measured. Results Water Quality and Vegetation C over age Morning water temperature ( o C) and dissolved oxygen (mg/L) levels never fell outside culture conditions proposed for bass and bluegill that directly relate to mortality (Boyd 1990). Morning oxygen levels below 3.0 mg/l were monitored closely to ensure levels increased to acceptable concentrations Reduced oxygen levels following drawdowns were pond specific and minimal at two and six months resulting in no related mortality (Figure 2 1). Mean, standard deviation (SD), and recorded ranges of morning dissolved oxygen, pH and total ammonia nitrogen data are summarized in Table 2 1 As with oxygen, recorded levels remained within ranges suggested for fish growth and survival (Boyd 1990). Percent vegeta tion bottom coverage was only esti mated by visual assessments Southern Naiad Najas guadalupensis and Muskgrass Chara sp comprised the majority of the submerged vegetation and algae with minimal emergent species including Pickerelweed Pontederia cordata and Knotgrass Paspalum disticum f ound around the edge s and shallow end of the ponds. Drawdowns minimally effected the Muskgrass
40 with the top layers desiccated by sun exposure, but no large scale loss drastically reducing coverage was observed in any pond replicate during the one year stu dy. Survival/Mortality Early post stock data indicated an initial difference in performance in favor of the Hatchery Forage treatment, but no survival or performance difference existed between pellet reared and live reared bass after one year. Individual cohort and total pond survival percentages listed in Table 2 2 represent ed survival from initial stocking, not between sampling periods unless specifically mentioned. Survival after two months showed no significant difference ( F (2 17 ) = 2.605; P = 0 1229 ) between Hatchery Standard 82.7% (5.8) (mean Standard Deviation), Hatchery Grade out 77.8% (5.3), and Hatchery Forage 88.0% (13.5) bass (Figure 2 2 ). Total pond population survival from all six ponds averaged 82.8% (6.4). Census data revealed a signi ficant difference in survival between treatments ( F (2,17) = 5.780; P = 0.0215) at six months post stock. (9.1) and Hatchery Forage 50.5% (7.3) ( P = 0.524) or Hatchery Stan dard and Hatchery Grade out 38.6% (7.7) ( P = 0.117) bass, but Hatchery Forage bass survived significantly better ( P = 0.0187) than Hatchery Grade out bass. Total pond population survival averaged 45.2% (6.3). Hatchery Standard, Hatchery Grade out, and Hat chery Forage treatment survivals 10.9% (7.3), 12 .5% (6.0), and 9.8% (6.1) showed no significant difference ( F (2,17) = 0.863, P = 0.4512) after 12 months post stock (Figure 2 2 ). Total pond population survival averaged 11.1% (5.8) (Table 2 2 ). Final analy sis showed relatively equal survivability of the three treatments one year post stock suggesting a specific hatchery rearing technique as reported in this study, did not sig nificantly produce a long term survival advantage.
41 I nstantaneous mortality rates (Z) were calculated to allow comparison of mortality rates regardless of differences in the length of time between sampling dates. The data showed when the greatest loss rates occurred between cohorts and across the three sampling periods for an individua l cohort (Figures 2 3 and 2 4 ). No si gnificant mortality differences were found between cohorts ( F (2,17) = 2.197, P = 0.1618) two months post stock (61 d interval) No significant differences among all three groups occurred during the 122 d May through September period ( F (2,17) = 1.192, P = 0.343) (Table 2 3 ). The final 169 d period, September through March, revealed significant differences between treatments ( F (2,17) = 9.804, P = 0.0044 (Table 2 3 ). Hatchery Standard and Forage bass mortality rates w ere significantly greater ( P = 0.0133 and P = 0.0039) than the Hatchery Grade out mortality rate. The difference in mortality rates between Hatchery Standard and Hatchery Forage bass ( P = 0.2177) were not significant (Table 2 3 ). Final analysis showed rel atively equal mortality between the Hatchery Standard and Forage treatments, but provided support for seasonal affects possibly creating an advantage for the larger Hatchery Grade out bass. Compared mortality rates of each Hatchery Standard, Hatchery Grad e out, or Hatchery Forage treatment showed significant differences in mortality in individual treatments across the three sampled periods (Figure 2 4 ). Hatchery Standard ( F (2,17) = 5.477, P = 0.0248) and Hatchery Forage bass ( F (2,17) = 5.635, P = 0.0230) treatments experienced significantly greater mortality during the September March period compared to the March May or May September periods. No differences in mortality rates were found over the three sampled time periods for the Hatchery Grade out treatment ( F (2,17) = 1.205, P = 0.3397) (Figure 2 4 ).
42 Growth All data reported in this section compare cumulative growth from initial stocking date ( not growth increments between the individual sampling events ) Length and weight data from 50 bass per pond ( 25% of each cohort ) was collected at stocking Length and weight data from 50 bass from each cohort per pond were similarly recorded at the two and six month census samples equating to approximately 33% and 50% of the cohort populations, respectivel y. The final 12 month harvest recorded all remaining bass lengths and weights. The length data from all six ponds was pooled together to display how the size frequencies changed for each cohort over the one year experiment (Figure 2 5 ). Histograms show s imilar sizes between the Hatchery Standard and Forage treatments after 12 months and Hatchery Grade out bass remained larger throughout the study duration. Significant differences for mean lengths and weights are displayed in Table 2 4 The full compari sons for length, weight and growth rates for each sampling event s GLMM analyses are displayed in the appendix. Post hoc tests results remained in the text as needed. Lengths and weights of the Hatchery Standard Hatchery Grade out, and Hatchery Forage bass were significantly different 100.5 (8.9), 117.2 (14.9), and 87.8 mm (6.5); 12.5 (3.9), 21.14 (9.5), and 7.08 g (1.5) from each other at initial stocking in March 2013 (Table 2 4 ). The remainder of this section (SD) will not be reported in the text as they were reported in Table 2 4 Two months post stock, the average lengths and weights remained significantly different between the Hatchery Standard, Hatchery Grade out, and Hatchery Forage treatments and 128.1, 146.7, and 120.2, mm; 19.1, 29.9, and 16 .3 g. Mean population growth comparisons in this two month period showed Hatchery Forage bass mean growth 32.3 mm was significantly greater
43 than Hatchery Standard bass mean growth 27.5 mm ( P = 0.0316). These values were converted to daily growth rate, 0. 54 mm/d and 0.46 mm/d, respectively (Table 2 4 Figure 2 6 ). The a ctual growth comparisons at harvest dates exposed meaningful trends between the three cohorts that are not revealed by the cumulative final lengths and weights achieved at each harvest even t. Six months post stock there were no significant differences in mean length or weight between Hatchery Standard and Hatchery Forage bass treatments 155.5 mm and 151.8 mm; 37.2 g and 35.9 g, but both w ere significantly smaller than Hatchery Grade out mean length 176.3 mm and weight 59.1 g ( P < 0.00001) (Table 2 4 ). Mean population length and respective growth rate (mm/d) six month harvest data showed Hatchery Forage bass continued significantly greater mean length increases 64.0 mm (0.35 mm/d) compare d to Hatchery Standard bass 55.0 mm (0.3 mm/d) ( P = 0.0022). No differences in mean population weight and growth rate (g/d) occurred 28.8 g (0.16 g/d) and 24.4 g (0.13 g/d), respectively. Hatchery Grade out bass mean population growth and rate by length 59.1 mm (0.32 mm/d) was not significantly different than the Hatchery Standard and Hatchery Forage treatments, but significantly increased by mean weight and growth rate 37.9 g (0.21 g/d) over both ( P < 0.0015) (Table 2 4 ). The final 12 month sample sho wed no significant differences after one year post stock in final mean length, weight, actual growth in mm of g or (mean growth rate) between hatchery reared pellet fed Hatchery Standard bass and live forage raised Hatchery Forage bass; 173.1 mm, 51.5 g, 72.6 mm (0.21 mm/d), 39.0 g (0.11 g/d) and 166.5 mm, 44.8 g, 78.8 mm (0.22 mm/d), 37.7 g (0.11 g/d), respectively (Table 2 4 Figure 2 6 ). The pellet reared Hatchery Grade out bass domi nated in both length and
44 weight with significant differences from both Hatchery Standard and Hatchery Forage bass in final mean length, weight, mean growth, or (mean growth rate); 222.6 mm, 136.4 g, 105.5 mm (0.3 mm/d), 115.2 g (0.33 g/d) (Table 2 4 Figure 2 6 ). Mean lengths and weights at each sampling period showed stron g similarities between the Hatchery Standard and Hatchery Forage bass as well as the increased Hatchery Grade out bass growth in the last 6 months (Figure 2 7 ). Final 12 month growth differences were visually documented in Figure 2 8 Condition factors ( K) compared the condition of the three treatment populations at initial stocking and the three samples dates. Initially Hatchery Standard, Hatchery Grade out, and Hatchery Forage cohorts K values were significantly different 1.20, 1.24, and 1.04, respecti vely (Table 2 5 ). Condition factors at final harvest revealed no significant difference between Hatchery Standard an d Hatchery Forage, 0.90 and 0.92 treatments. The 1.06 Hatchery Grade out K value was significantly better than both. The K values were u sed to provide quantitative data to help possibly explain mortality and growth results. Discussion Survival/Mortality Survival of fish produced by the different hatchery treatments was compared across six replicate ponds from initial stocking date (March 23, 2013) at each of the three sampling dates. The ponds were devoid of wild age 0 bass whi ch would compete with hatchery bass if they existed in the ponds No significant survival differences between treatments were found two months post stock. The onl y observed difference in survival at six months post stock occurred be tween the Hatchery Grade out a nd Hatchery Forage treatments. Hatchery Standard and Hatchery Forage bass surviva l were not significantly different at six months post stock, but the large r Hatchery Grade
45 out bass survival was significantly less than the Hatchery Forage treatment. Published comparable hatchery produced bass stocking survival data from census sampling is elusive at six months post stock with comparisons further complicated by differing rearing methods and reported analysis. Buckmeier et al. (2003) reported 28 66 mm live reared (zooplankton) fingerling stocked at 10,000 and 100,000/site contributed 5.4 and 14.9% per site to the age 0 cohort five months post stock. Year cl ass contributions for four years of stocking live reared Florida bass (65 90 mm) in Lake Talquin were 36, 22, 40, and 17% six months post stock (Mesing et al. 2008). Mean contributions from five years of stocking 89 160 mm minnow rea red and pellet reare d or pellet reared finished with minnows for 14 days in a 2,819 ha southern Illinois reservoir averaged 9.3 and 6.6% of the total age 0 fall year classes. Adjusting these numbers to only include stocked cites increased percent contributions to 12.0 and 7. 8%, respectively (Heidinger and Brooks 2002). Percent contribution data is not comparable with my survival data and are utilized here to show both forage and pellet reared hatchery bass are surviving. Final harvest 12 months post stock found no signifi can t difference in survival among the Hatchery Standard, Hatchery Grade out, and Hatchery Forage treatments, 10.9, 12.5, and 9.8%, respectively. Co hort survival was fairly similar within ponds, but variable between ponds. The importance of this data for stock enhancement pertains to the relative similarities or difference between survival of hatchery treatments and not the actual recorded numeric al value. The simil arity in survival across all treatments two months post stock was higher than expected based on previous study results in hatchery ponds at the FBCC (Porak et al. 2011). Pooling three years of hatchery trials compared survival of pellet reared
46 bass conditioned in raceways for 5 d on mosquito fish (1 to 2 minnows/day/bass) to live reared bass af ter 30 d in ponds showed significantly lower pellet reared bass survival, 36% compared to 53% survival in live reared ba ss (Porak et al. 2011). S urvival in the current study w as greater (77 88% ) most likely due to the lower predator population densities, 13/ha in our ponds versus their 56/ha, possible greater percentage plant and algae refuge longer time frame used to condition the bass to live forage and possible reduced initial post stock movement time due to stocking small hatchery ponds Our study d uration was 12 months opposed to one month with 25, 68, and 70% estimated mean visual percent plant and algae coverage across the six treatments at 2, 6 and 12 months post stock. The estimated 25% vegetation coverage two months post stock was comparable t o reported coverage levels that reduced mortality for similar sized age 0 bass stocked in ponds with 52 (250 350 mm) predator bass/ha (Miranda and Hubbard 1994 ) with elevated plant coverages departing from levels normally found in natural lakes, at 6 and 12 months likely increasing protection from predation (Durocher et al. 1984 ; Bettoli et al. 1992 ) Wiley et al. (1984) suggested surface area coverage greater than 36% may negatively affect bass growth due to increased survival and needs consideration whe n applying my results to future stocking projects. The increased refuge may have influenced over all survival in this study but effects were most likely sha red equally among treatments. Comparisons be tween treatments would be more a ffected if one or mor e treatments were purposely allowed a shelter related advantage over the other treatment(s). We do not suspect this particular advantage occurred in our ponds. She lter related benefits from predators were shown to wane as age 0 bass lengths increased pas t 125 mm TL (Miranda and Hubbard 1994), but this
47 likely resulted from small sized (TL) predator populations used in their study. Increasing predator densities in my ponds may have decreased survival at the two and six month samples and possibly accounts f or the counter intuitive inverse mortality pattern The low predator density possibly initially reduced observing treatment survival difference s but better simulated applicable stocking situations. Ou d on live feed (4 min nows/ day/bass), closely mimicked Rachels et al. (2005) assessment that predicted pellet reared bass exposed to minnows for 9 days pre stock would have similar ability to wild bass to compete for food. The exposure to live prey definitely helped transitio n the bass to forage, but may This may explain the initial better growth performance for the live reared bass. Studies in natural lakes also reported significan tly lo wer survival occurring 30 d post stock compared to true wild bass (not hatchery reared) due to elevated movement out of protective habitat and poor initial foraging skills (Pouder et al. 2010 ; Thompson 2012 ). Additional work presented evidence of no long term survival or growth rate disadvantage of released hatchery bass after an initial post stocking movement 19 day period (Jackson et al. 2002) as commonly expected (Parker 1986). Dispersal related mortality was reported to stabilize after a similar time period (Buckmeier and Betsill 2002 ; Hoffman and Bettoli 2005 ) suggesting a short term post hatchery induced behavior. The small 0.24 0.28 ha sized hatchery ponds possibly reduced initial movement longevity as bass likely acclimate d quicker to the small pond environments
48 Mortality rates analyzed data between the sampling dates helped compare and interpret specific mortality differences and occurrences between hatchery treatments under conditions specified in this study. Standard izing mortality to mean daily rates (Z) allowed me to compare mortality rates between study periods. C omparing individual cohort daily instantaneous mortality rates across the three sample periods showed lower mortality in the first two months post stock, a slight increase during the second sampled period, and then highest rates during the last sample period. Similar mortality rates between Hatchery Standard and Hatchery Forage bass treatments suggest different advanced rearing protocols failed to singula rly i nfluence mortality in our study and align with previous data that sugg ested hatchery induced eff ects may be more attributed to high nursery pond rearing densities (Austin et al. 2012). Still, the low predator density possibly initially reduced observ ing treatment survival differentiation needs consideration. Increased mor t ality initially following stocking live reared bass was reported at 27.5% 12 h post stock in a Texas reservoir (Buckmeier et al. 2005) and documented in other natural and laboratory evaluations utilizing live or pellet reared bass (Schlechte et al. 2005 ; Pouder et al. 2010 ). Hatchery origin b ass less tha n 126 mm showed increases in survival as the percentage of brush cove r increased (Miranda and Hubbard 1994 ). These factors help e xplain our two month mortality data as large bass are very cannibalistic on stocked bass, but fails to completely account for mortality results recorded over the entire study. The Hatchery Grade out bass experienced significantly lower mortality compared to the Hatchery Standard and Hatchery Forage treatment during the last six month sample period. Condition factors during this time frame were significantly better for the
49 Hatchery Grade out treatment compared the Hatchery Standard and Hatchery Forage trea tments and supports the hypothesis that survival over wi nter is potentially size depende nt. It is possible that small portions of the Hatchery Standard and Forage bass were vulnerable to predation by the largest of the Hatchery Grade out bass toward the e nd of the study. This is not uncommon in age 0 natural bass recruitment and again supports age 1 recruitment is possibly size dependent. The larger bass were able t o remain on forage that out grew the smaller Hatchery Standard an d Hatchery Forage treatme nts S ize selective over winter mortality importance is debated in LMB cohort dynamics across latitudes (Ludsin and DeVries 1997; Jackson and Noble 2000; Rogers and Allen 2009). Fullerton et al. (2000) reported winter survival was size dependent in tw o of three trials on LMB and origin (northern or southern climates) and availabl e forage needs consideration. Body size was reported as a primary factor influencing over winter survival in Missouri lakes (Gutreuter and Anderson 1985), but considered an ir relevant factor in supplemental stocking data from a reservoir in Puerto Rico (Neal et al. 2002). Pine et al. (2000) suggested early hatched bass (minus stochastic negative weather events) have a greater chance of recruitment to the age 1 year class prima ry based on larger sizes achieved prior to first winter in warmer southern climate systems with extended spawning windows. Our results show that over winter size dependent mortality could explain why the significantly larger Hatchery Grade out bass experi enced comparatively reduced mortality the last six month period and posted the highest observed fina l survival one year post stock.
50 Hatchery Reared Compared to Wild Survival It is instructive and insightful to compare the mortality rates suffered by hatch ery reared largemouth bass in my experiments with comparative data on mortality rates of wild and released hatchery reared fish as reported in Lorenzen (1996; 2006). Mortality rates in my experiments averaged 3.6 year 1 for fish of an average length of ab out 160 mm. This compares to median mortality rates at this length of 1.0 year 1 for wild fish and 4.2 year 1 for hatchery fish released into the wild. Post release mortality in my experiments therefore is broadly in line with expectations for released ha tchery fish, and substantially higher than would be expected for wild fish. Possible experiences relating this common hatchery linked mortality phenomenon include differing spawning techniques, broodstock origin, and elevated rearing densities. Hhn et a l. ( 2014) demonstrated stocking hatchery reared pike fry, devoid of suspected deleterious effects fro m manipulated (no natural selection) spawning techniques increased survival compared to broo d stock with the same genetic origin. Ultimately, stocking was still only additive in the absence of wild natural recruitment, but the manipulated hatchery fry still showed a competitive disadvantage to fry collected from more natural pond spawning conspecifics. Fritts et al. (2007) reported wild Chinook salmon Onco rhynchus tshawytscha fry retained a slight but significant 2.2% survival advantage over first generation hatchery fry from the same wild hatchery stock. Effects from the culture environment increased predation vulnerability in the salmon fry in controlled environments. Elevated pond or raceway stocking and rearing densities may alter behavioral traits increasing aggressiveness and leading to increased mortality in hatchery reared fish post stock in natural, more complex environments (Huntingford 2004; Lor enzen et al. 2012).
51 Lower survival of the larger Hatchery Grade out cohort was counter intuitive presuming large stocked bass should have a greater chance at survival, but altered behavior from artificial rearing environments and genetic predisposition m ay help explain the reduced survival. Presuming the Hatchery Grade out bass achieved larger sizes by more aggressive feeding behavior, early switch to cannibalism on conspecifics, or both, this more active foraging behavior in unprotected areas would have increased vulnerability to predation. Separate research projects at the FBCC reported pellet reared hatchery bass (approximately 100 mm) were considerably more active and experienced significantly lower survival compared to true wild bass (approx. 132 mm ) stocked in hatchery ponds with predators. Activity matters: m odel analysis five weeks post stock showed that total length or total length plus activity were strong predictor s of survival (Garlock et al. 2014). Monk (2013) also reported increased activi ty and boldness in pellet reared bass compared to true wild bass in research tanks, and reported pellet reared bass spend significantly more time (3 to 4 times) in close proximity to larger bass predators then true wild bass. Thompson (2012) suggested red uced survival of between pellet reared bass (106 1.62 mm) compared to true wild bass (110.7 1.53 mm) in a natural lake was related to higher movement in open water habitats and poor foraging efficiency increasing vulnerability to predation. These studi es do not definitively explain the survival difference b etween the three treatments but provide some insight for their similarity and on survival differences of hatchery and wild fish. Growth and Performance Mean population lengths and weights achieved b y the Hatchery Grade out bass treatment remained significantly greater than both Hatchery Standard and Hatchery
52 Forage bass at each harvest date. The Hatchery Standard and Hatchery Forage mean population lengths and weights were only significantly differen t at the 2 month harvest. The data simply compares mean lengths and weights at sample points and does not account for the initial significant differences in size between the cohorts. Performance analysis accounted for initial stocking differences between the treatments and reve a led differences between cohorts. Hatchery Forage bass significantly out performed the Hatchery Standard bass in growth rate (mm/d) at the two month and six month sampling periods and Hatchery Grade out bass out performed Hatchery S tandard and Hatchery Forage bass in growth rate (g/d) at six months post stock and grew faster than both cohorts in length and weight 12 months post stock. The effect of raceway rearing dissipated with no difference in Hatchery Standard and Hatchery Forag e bass growth rates observed after 6 months. Lower condition factors for both pellet reared treatments (significantly different for Hatchery Standard bass) compared to the Hatchery Forage bass two month post stock rel ates initial poorer performance possib ly due to increased activity and reduced foraging skills. Reduced foraging skills were evident initially in both pellet reared treatments with respect to comparative slower growth rates and lower condition factors (Tables 2 4 and 2 5 ). Pouder et al. (20 10) determined that hatchery bass had difficulty transitioning from pellets to live prey 7 d after being released reporting significantly more empty stomach then the age 0 wild bass produced in the lake, but fish consumption and empty stomachs were not fou nd significantly different between the same groups 14 d post stock. No difference in K values between Hatchery Standard and Hatchery Forage bass treatments were observed after two months post stock.
53 We found no significant difference between the larger Hatchery Grade out bass and the Hatchery Forage bass in growth rate in length or K value until final harvest at 12 months, both in favor of the Hatchery Grade out bass. The Hatchery Grade out bass significantly out performed the Hatchery Forage bass in gr owth rate by weight after the first two mont hs. This provided evidence of short term reduced foraging skills even in the more aggressive larger pellet reared bass treatment. The growth rates in our study were comparable to reported age 0 hatchery produce d and wild bass in other studies Jackson et al. (2002) reported similar individual age 0 bass growth rates (July November) averaged 0.18 and 0.3 mm/d for live reared (assumed) hatchery bass and 0.14 and 0.20 mm/d for wild bass in a North Carolina reser voir in two consecutive years. Our six month (March 23 September 23) growth rates were similar to nine years of reported wild bass growth rates (range 0.05 to 0.39 mm/d) collected July October on the same North Carolina Reservoir (Jackson and Noble 200 0). The similar reported growth rates provides support for our ponds producing adequate forage abundance as only estimated predator/prey ratio data for analysis was attained Forage abundance was not rigorously measured at the two and six month sample pe riods but large amounts of fry and fingerling were observed. Warm temperatures and diminished water quality concerns hindered obtaining equally comparable census data on forage in each pond replicate at two and s ix month census dates, but total weight estimates and size ranges were observed. The available forage amounts at initial bass stocking were unknown. Comparing our bass length data at the two and six month samples using mouth gape width/total length relationships ( Hambright 1991 ; Hill et al. 20 04 ) for bass to the observed forage available sizes
54 suggested forage limitation was unlikely. Actual abundance of forage remained unattained at the two an d six month sampling, but was marginally accessed utilizing bass condition factor and growth rate co mparisons mentioned earlier Consistent mean K values near 0.9 and 1.0 two and six months post stock across the six replica te ponds for each treatment supports forage was adequate. Total forage base was only quantified in each pond at final harvest. Amp le Lepomid spp. forage remained at final 12 month harvest, 88 to 234 k g/ha, for bass in all 6 ponds. Weight of available forage comp ared to total bass weight in kg remained > 3:1 in all six treatment ponds, approached ratios described by (Simco et al. 198 6) for quality bass growth. Representative population lengths were collected and Lepomid spp. lengths ranged from 15 to 150 mm with the majority falling betw een 25 and 65 mm. F orage availability may have shifted in favor of the larger Hatchery Grade out bass at some point during the last six months as their larger size would allow consumption of larger size range s of the available fish up to approximately 150 mm TL based on length frequency ranges reported in Figure 2.4 This possibly contributed to th eir significant ly increased growth rates recorded between September and March and evident by the 12 month K value increase comp ared to the six month K value. Potential C onfou nding Effects of Inter cohort Interactions and D rawdown s Increased size may have r educed the Hatchery Grade out treatments predation availability (Miranda and Hubbard 1994) resulting in a comparative d ecrease in mortality during the September March final time period. Additionally, their increased size may have allowed the largest of the Hatchery Grade out treatment bass to prey on the smallest of the Hatchery Standard and Forage treatments. Inter cohort cannibalism was not suspected to significantly contribute to mortality in the two and six month
55 samples as length frequency data s howed bass size ranges below the 2:1 predator to prey length ratio suggested by Johnson and Post (1996) because of the maximum size that an age 0 bass of a given length can consume Comparisons pertaining to Hatchery Grade out bass need to consider their initial greater size, but these effects, if any, would equally influence the Hatchery Standard and Forage treatments minimally impacting their respective comparative outcomes. The three complete drawdown samples to the kettle concentrated all the fish poss ibly increasing predation, but the short duration, eq ual effects across treatments ( 2 and 6 month samples), and low predator density minimizes effects concerning the head to head comparison. The 12 month final sample may have allowed for increased predati on on the Hatchery Standard and Forage treatments possibly impacting survivability comparis ons between these treatments with the Hatchery Grade out treatment. Similar sizes of the Hatchery Standar d and Hatchery Forage treatment s suggests equivalent vulner ability to predation minimizing the possibl e effects of cannibalism form the Hatchery Grade out bass concerning survival comparisons between these two treatments. The drawdow n s did not noticeably affect plant coverage with minimal loss to refuge structure and no significant water qual i ty induced changes observed post draw dow n (Figure 2 1). Loss of fry sized forage during drawdowns at 2 and 6 months was minimal based on observations of forage in the harvest kettle. Although unconfirmed by direct measuremen t condition factions across tr eatments support this statement Utility for Culture Based Fisheries Management Enhancement research advances that integrate aquaculture and fisheries sciences provide future guidance and unique opportunities to learn more a bout natural
56 fish populations. Good scientific guidance resulting from such research needs wider application (Lorenzen 2014). Success of stocking Largemouth bass depends on a long list of variables that must be cautiously examined for adequate comparison Unfortunately, in many trials valuable information including age structure, predator densities, and age 0 bass populations ar e unknown or poorly estimated. The controlled environments of my six pond replicates removed most of these unknowns. The imp ortance of this data demonstrates that survivab ility was not affected solely by hatchery rearing technique as bass produced from wild caught parents one year post stock were no different Differing natural environments and pre existing fish communities wi ll effect final survival outcomes, but the intention of this research was not to predict actual survivability. Implications from my resu lts allow hatcheries options to efficiently produce advanced hatchery bass pellet rearing reducing hatchery spatial co sts associated with pond reared advanced fingerling, without significantly sacrificing product potential. The high mortality in stocked culture d fish in most cases should not be solely attribut ed to domestication effects, as high mortality measures ar e experienced by un stocked age 0 wild populations (Lorenzen 1996) Considering the gauntlet of mortality hatchery bass have to swim through, size at stocking, predator densities, domestication, life skills education, etc., it seems reasonable to expect l ow survival to age 1post stock in natural systems (Olla et al. 1998; Weber and Faus ch 2003; Huntingford 2004). My study elicited only an average 11% survival one year post stock in ponds with low predators no natural age 0 bass adequate forage, and ampl e refuge. The data was not intended to set levels of stocking success or failure for futu re stocking projects and
57 should be considered a with more reasonable expected values ranging from 1 to 8% in pre existing natural predator populations (Porak et al. 2002; Lorenzen 2006 ; Mesing et al. 2008; FWC 2013). The primary focus of this research concerned the evaluation between the Hatchery Standard and Hatchery Forage bass treatments. The Hatchery Grade out bass essentially are Hatch ery Standard bass as rearing protocols were identical. The inclusion of the Hatchery Grade out cohort was to evaluate the long term resilience of the increased growth rates and to illicit data to determine if this growth outcome could be governe d genetica lly (Domingos et al. 2013; Sakmar 2013). Broodfish were genetically identified and parentage assignment positively link offspring to parent (Barth el et al. 2010). Sakmar ( 2013) showed that Hatchery Grade out bass came from a sub set of the total parent p opulation and that more than 80% of the Hatchery Grade out bass resulted from the pairing of two specific individuals. The fingerlings used in (2013) and our study resul ted from that same 29 spawns. Figure 2 6 showed that the increased growth ra te persisted after a year post stock in ponds on natural incorporate stocking t hese fish as they can positively contribute to future fisheries and
58 Table 2 1. Mean () standard deviation and range of morning dissolved oxygen (mg/L), pH, and total ammonia nitrogen (mg/l) in each of the six po nd replicates stocked with 600 Florida bass in March 2013 and harvest March 2014. Pond 9 Pond 10 Pond 17 Pond 18 Pond 34 Pond 35 Parameter Morning Oxygen, mg/l Mean (SD) 5.1 (0.9) 5.1 (0.9) 4.7 (0.6) 4.8 (0.6) 4.8 (0.6) 4.5 ( 0.6) Range 3.2 7.0 2.4 7.1 3.5 6.1 3.5 6.2 2.8 6.0 2.8 5.8 pH Mean (SD) 7.5 (0.4) 7.5 (0.3) 7.5 (0.3) 7.5 (0.3) 7.4 (0.4) 7.5 (0.4) Range 6.9 8.6 6.7 8.1 6.9 7.9 6.9 7.9 6.7 8.3 6.4 8.5 Total Ammonia Nitrogen, mg/l Mean (SD) 0.05 (0.1) 0.06 (0.1) 0.05 (0.1) 0.05 (0.1) 0.06 (0.1) 0.06 (0.1) Range 0.0 0.4 0.0 0.5 0.0 0.5 0.0 0.4 0.0 0.5 0.0 0.4
59 Table 2 2 Percent survival calculated from initial numbers (N = 200) of Hatchery Standard (HS), Hatchery Grade out (HG), and Hatchery F orage (HF) cohort Florida bass and total survival per pond (N = 600) at 2, 6, and 12 month post stock census from six replicate ponds in Webster, FL. Differences in mean s ( standard deviation ) numeric superscripts Hatchery Standard and Hatchery Grade out bass were pellet reared and conditioned to forage (minnows) for eight days post stock. Hatchery Forage bass were reared in ponds on natural fora ge 2 Month, May 2013 6 Month, Sept 2013 12 Month March 2014 Pond HS HG HF Total HS HG HF Total HS HG HF Total Survival,% Pond 9 73.5% 71.5% 81.0% 75.3% 45.0% 27.0% 50.5% 40.8% 13.5% 11.0% 18.5% 14.3% Pond 10 79.0% 73.0% 87.0% 7 9.7% 42.0% 34.0% 43.0% 39.7% 7.5% 14.5% 7.5% 9.8% Pond 17 89.0% 75.0% 100.0% 88.0% 54.0% 38.5% 43.5% 45.3% 20.0% 14.5% 12.5% 15.7% Pond 18 84.5% 80.5% 65.0% 76.7% 53.0% 42.2% 61.0% 52.1% 1.0% 2.2% 0.5% 1.2% Pond 34 88.0% 84.3% 100.0% 9 0.8% 54.0% 49.7% 57.0% 53.6% 17.5% 20.5% 12.5% 16.8% Pond 35 82.0% 82.2% 95.0% 86.4% 31.0% 40.0% 48.0% 39.7% 6.0% 12.4% 7.5% 8.6% Mean 82.7% a 77.8% a 88.0% a 82.80% 46.5% a,b 38.6% b 50.5% a 45.2% 10.9% a 12.5% a 9.8% a 11.1% S t. Dev. (5.8) (5.3) (13.5) (6.4) (9.1) (7.7) (7.3) (6.3) (7.3) (6.0) (6.1) (5.8) Superscripts a and b represent significant differences between treatments at P = 0.05.
60 Table 2 3 Instantaneous mortality of Hatchery Standard (HS), Hatchery Gr ade out (HG), and Hatchery Forage (HF) Florida bass between stocking 2 months, 2 6 months, and 6 12 months post stock census in six replicate ponds in Webster, FL. Total represents the average combined mortality rate per pond re plicate. Differences in mean s ( standard deviation ) between cohorts (not represented by numeric superscripts were compared. The differing lengths of duration and remaini ng bass in each time period standardized by day f or analysis and comparison were 61, 122, and 169 days, respectively. March to May 2013 May to Sept 2013 September 2013 to March 2014 Pond HS HG HF Total HS HG HF Total HS HG HF Total Mortality rate, Z /d Pond 9 0.0050 0. 0055 0.0035 0.0047 0.0040 0.0080 0.0039 0.0053 0.0071 0.0053 0.0059 0.0061 Pond 10 0.0039 0.0052 0.0023 0.0038 0.0052 0.0063 0.0058 0.0057 0.0102 0.0050 0.0103 0.0085 Pond 17 0.0019 0.0047 0.0000 0.0022 0.0041 0.0055 0.0068 0.0055 0.0059 0. 0058 0.0074 0.0063 Pond 18 0.0028 0.0037 0.0071 0.0045 0.0038 0.0053 0.0005 0.0032 0.0235 0.0176 0.0284 0.0232 Pond 34 0.0021 0.0029 0.0000 0.0017 0.0040 0.0043 0.0046 0.0043 0.0067 0.0020 0.0090 0.0059 Pond 35 0.0033 0.0033 0.0008 0.0024 0 .0080 0.0059 0.0056 0.0065 0.0097 0.0069 0.0110 0.0092 Mean 0.0032 a 0.0042 a 0.0023 a 0.0032 0.0048 a 0.0059 a 0.0045 a 0.0051 0.0105 b 0.0071 a 0.0120 b 0.0099 St. Dev. (0.0012) (0.0011) (0.0027) (0.0013) (0.0016) (0.0012) (0.0022) (0.0012) (0.0066) (0.0054) (0.0083) (0.0066) Superscripts a and b
61 Table 2 4 Cumulative mean (standard deviation ) population lengths (millimeters) and weights (grams), mean population growth, and growth rate per day from initial stock da te (N = 300 pe r cohort) collected from n = 50 Hatchery Standard (HS), Hatchery Grade out (HG), and Hatchery Forage (HF) Largemouth Bass per pond at initial sto cking, two, and six months post stock from six replicate ponds in Webster, FL. All remaining bass harvested 12 months post stock were sampled. Differences in means ( standard deviation ) between cohorts were represented by numeric superscripts Stocked, March 2013 2 Month, May 2013 6 Month, Sept 2013 12 Month March 2014 Treatment M m g mm g mm g mm g Lengths and Weights HS 100.5 (8.9) a 12.5 (3.9) a 128.1 (8.4) a 19.1 (4.5) a 155.5 (12.6) a 37.2 (11.2) a 173.1 (18.1) a 51.5 (24.5) a HG 117.2 (14.9) b 21.14 (9.5) b 146.7 (16.7) b 29.9 (11.1) b 176.3 (24.6) b 59.1 (30 .5) b 222.6 (40.3) b 136.4 (83.0) b HF 87.8 (6.5) c 7.08 (1.5) c 120.2 (6.5) c 16.3 (3.0) c 151.8 (10.0) a 35.9 (10.7) a 166.5 (14.0) a 44.8 (15.6) a Mean growth HS N/A N/A 27.5 (1.0) a 6.7 (1.4) a 55.0 (7.7) a 24.4 (8. 4) a 72.6 (13.7) a 39.0 (16.1) a HG N/A N/A 29.5 (4.9) a,b 8.8 (3.2) a 59.1 (6.4) a,b 37.9 (8.9) b 105.5 (14.4) b 115.2 (32.3) b HF N/A N/A 32.5 (2.2) b 9.3 (0.9) a 64.0 (8.1) b 28.8 (7.2) a 78.8 (12.2) a 37.7 (11.5) a Mean growth rate/day HS N/A N/A 0.46/d a 0.11/d a 0.3/d a 0.13/d a 0.21/d a 0.11/d a HG N/A N/A 0.49/d a,b 0.15/d a 0.32/d a,b 0.21/d b 0.3/d b 0.33/d b HF N/A N/A 0.54/d b 0.15/d a 0.35/d b 0.16/d a 0.22/d a 0.11/d a Superscripts a,b,c represent si
62 Table 2 5 Mean population condition factors (K) for Hatchery Standard (HS), Hatchery Grade out (HG), and Hatchery Forage (HF) cohort Florida bass at initial stocking, 2, 6, and12 month post stock census from six re plicate ponds in Webster, FL. A total sample size of n = 50 bass per pond represent the initial, two, and six month data wit h all remaining bass sampled at 12 months. Differences in means ( standard deviation ) between cohorts were represented by numeric s uperscripts. Initial Stock, March 2013 2 Month, May 2013 6 Month, Sept 2013 12 Month March 2014 Pond HS HG HF HS HG HF HS HG HF HS HG HF Condition Factor, K Pond 9 1.20 1.21 1.03 0.89 0.90 0.93 0.95 0.97 0.97 0.97 1.06 0.98 Pond 10 1.19 1.23 1.03 0.88 0.93 0.93 0.84 0.92 0.92 1.00 1.11 0.97 Pond 17 1.20 1.22 1.04 0.88 0.94 0.95 1.04 1.04 1.05 0.86 1.05 0.91 Pond 18 1.19 1.25 1.06 0.89 0.89 0.92 0.86 0.89 0.93 0.78 1.11 0.88 Pond 34 1.20 1.26 1.03 0.91 0.91 0.96 0.99 1.02 1.04 0.85 0.96 0.84 Pond 35 1.21 1.28 1.04 0.93 0.93 0.92 1.00 1.13 1.03 0.94 1.09 0.91 Mean 1.20 a 1.24 b 1.04 c 0.90 a 0.92 a,b 0.94 b 0.95 a 1.00 b 0.99 a,b 0.90 a 1.06 b 0.92 a St. Dev. (0.0075) (0.0264 ) (0.0117) (0.0197) (0.0197) (0.0164) (0.0804) (0.0873) (0.0576) (0.0837) (0.0565) (0.0532) Superscripts a,b,c
63 0 5 10 15 20 25 30 35 0 1 2 3 4 5 6 7 8 3/23/2013 4/6/2013 4/20/2013 5/4/2013 5/18/2013 6/1/2013 6/15/2013 6/29/2013 7/13/2013 7/27/2013 8/10/2013 8/24/2013 9/7/2013 9/21/2013 10/5/2013 10/19/2013 11/2/2013 11/16/2013 11/30/2013 12/14/2013 12/28/2013 1/11/2014 1/25/2014 2/8/2014 2/22/2014 3/8/2014 Temperature C Oxygen, mg/L Pond 18, Date Oxygen, mg/L Morning Temperature Figure 2 1. Morning oxygen (mg/l) and temperature ( o C) data recorded fro m six replicate ponds in Webster, Florida. 0 5 10 15 20 25 30 35 0 1 2 3 4 5 6 7 8 Temperature C Oxygen, mg/L Pond 9 Oxygen, mg/L Morning Temperature 0 5 10 15 20 25 30 35 0 1 2 3 4 5 6 7 8 3/23/2013 4/6/2013 4/20/2013 5/4/2013 5/18/2013 6/1/2013 6/15/2013 6/29/2013 7/13/2013 7/27/2013 8/10/2013 8/24/2013 9/7/2013 9/21/2013 10/5/2013 10/19/2013 11/2/2013 11/16/2013 11/30/2013 12/14/2013 12/28/2013 1/11/2014 1/25/2014 2/8/2014 2/22/2014 3/8/2014 Temperature C Oxygen, mg/L Pond 17, Date Oxygen, mg/L Morning Temperature 0 5 10 15 20 25 30 35 0 1 2 3 4 5 6 7 8 Temperature C Oxygen, mg/L Pond 10 Oxygen, mg/L Morning Temperature
64 Figure 2 1. Continued 0 5 10 15 20 25 30 35 0 1 2 3 4 5 6 7 8 3/23/2013 4/6/2013 4/20/2013 5/4/2013 5/18/2013 6/1/2013 6/15/2013 6/29/2013 7/13/2013 7/27/2013 8/10/2013 8/24/2013 9/7/2013 9/21/2013 10/5/2013 10/19/2013 11/2/2013 11/16/2013 11/30/2013 12/14/2013 12/28/2013 1/11/2014 1/25/2014 2/8/2014 2/22/2014 3/8/2014 Temperature C Oxygen, mg/L Pond 34, Date Oxygen, mg/L Morning Temperature 0 5 10 15 20 25 30 35 0 1 2 3 4 5 6 7 8 3/23/2013 4/6/2013 4/20/2013 5/4/2013 5/18/2013 6/1/2013 6/15/2013 6/29/2013 7/13/2013 7/27/2013 8/10/2013 8/24/2013 9/7/2013 9/21/2013 10/5/2013 10/19/2013 11/2/2013 11/16/2013 11/30/2013 12/14/2013 12/28/2013 1/11/2014 1/25/2014 2/8/2014 2/22/2014 3/8/2014 Temperature C Oxygen, mg/L Pond 35, Date Oxygen, mg/L Morning Temperature
65 Figure 2 2 Mean survival of Hatchery Standard, Hatchery Grade out, and Hatchery Forage Florida bass over a one year period in six replicate hatchery ponds in Webster, F L. Coded wire tags Right cheek (Hatchery Standard) and Left cheek (Hatchery Grade out) distinguished between pellet reared cohorts. The Hatchery Forage cohort was not tagged to restrict any short term domestication affects incurred during the tagging pro cess. Significant differences in survival were reported in Table 2 2 0% 20% 40% 60% 80% 100% 120% Stocked 2 Months 6 Months 12 months Survival over time Sampling duration post stock Hatchery Standard Hatchery Grade-out Hatchery Forage
66 Figure 2 3 I nstantaneous daily mortality estimates for Hatchery Standard, Hatchery Grade out, and Hatchery Forage Florida bass co habituated in six hatchery ponds (0.24 0.28 ha ). The sample times correspond to spring (March May), summer (May September), and fall winter seasons (September March) in central Florida, respectively. Significant differences between treatments were reported in Table 2 3 0.0000 0.0020 0.0040 0.0060 0.0080 0.0100 0.0120 0.0140 2 Months 2 -6 Months 6 12 Months Instantaneous daily mortality estimates Sample time frame Hatchery Standard Hatchery Grade-out Hatchery Forage
67 Figure 2 4. Inst antaneous daily mortality estimate comparison of Hatchery Standard (HS), Hatchery Grade out (HG), and Hatchery Forage (HF) Largemouth Bass co habituated in six hatchery ponds (0.24 0.28 ha) grouped by treatment. The sample times correspond to spring (Mar ch May), summer (May September), and fall winter seasons (September March) in central Florida, respectively. Vertical lines represent one standard deviation from the mean. The green columns include over winter mortality. 0.0000 0.0020 0.0040 0.0060 0.0080 0.0100 0.0120 0.0140 0.0160 0.0180 HS HG HF Instantaneous daily mortality estimates Treatment 2 Months 2 -6 Months 6 12 Months
68 A B Figure 2 5 Le ngth frequency distributions (total length, mm) of three cohorts of Florida bass census har vested 2, 6, and 12 months post stock from six pond replicates Initial stock A) two month B) and six month data C) distributions represent n = 300 (50 bass per c ohort per pond) and represente d a minimum of 25% of the each remaining pond population. The 12 month data D) represents all remaining bass harvested. 0 50 100 150 200 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 Stocked, n = 300/cohort Hatchery Standard Hatchery Grade-out Hatchery Forage 0 20 40 60 80 100 120 140 160 180 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 Frequency 2 Months, n = 300/cohort Hatchery Standard Hatchery Grade-out Hatchery Forage
69 C D Figure 2 5 Continued 0 10 20 30 40 50 60 70 80 90 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 6 Months, n = 300/cohort Hatchery Standard Hatchery Grade-out Hatchery Forage 0 5 10 15 20 25 30 35 40 45 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 Frequency Size group ( 10 mm), TL 12 Months, All remaining LMB (100+/cohort) Hatchery Standard Hatchery Grade-out Hatchery Forage
70 Figure 2 6 Cumulative mean population growth rate in A ) mm /day and B) g /day between initial stocking (March 2013) and 2, 6, and 12 months (May 2013, September 2013, and March 2014) post stock. (Significant differences HSD, were represented by different letter s). Data represents averaged ( n = 300) population growth at two and six months and all remaining bass harvested at 12 months. 0.00 0.10 0.20 0.30 0.40 0.50 0.60 Stocked 2 Months 6 Months 12 Months Growth rate, mm/day Growth Duration Hatchery Standard Hatchery Grade-out Hatchery Forage 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 Stocked 2 Months 6 Months 12 Months Growth rate, g/day Growth Duration Hatchery Standard Hatchery Grade-out Hatchery Forage A B
71 Figure 2 7 Cumulat ive mean population gro wth in A) mm and B) g between initial stocking (March 2013) and 2, 6, and 12 months (May 2013, Septe mber 2013, and March 2014) post stock. (Significant differences between treatments HSD, were shown in Table 2 4 ). Data represents averaged (n = 300) population increases at two and six months and all remaining bass harvested at 12 months. 0.00 50.00 100.00 150.00 200.00 250.00 Stocked 2 Months 6 Months 12 Months Length, mm Duration Hatchery Standard Hatchey Grade-out Hatchery Forage A 0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00 Stocked 2 Months 6 Months 12 Months Weight, grams Duration Hatchery Standard Hatchey Grade-out Hatchery Forage B
72 Figure 2 8 Photographical visual comparisons of Hatchery Standard A and D, Hatchery Forage B and E, and Hatchery Grade out C and F Florida bass harvested one year post stock from two of six replicate ponds. Initial size at stocking; Hatchery Standard 10 0.5 mm, Hatchery Forage 87.8 mm, and Hatchery Grade out 117.2 mm and final size s at harv est were reported in Table 2 4 ( Photos courtesy of author. ) A B C D E F
73 CHAP TER 3 ANG LING VULNERABILTY OF PELLET AND LIVE HATCHERY REARED FLORIDA LARGEMOUTH BASS > 250 mm St ock enhancement is used as a management tool to augment the productivity of healthy fish populations by increasing the density of a pre existing species or by introducing a new one (Boxrucker 1986, Churchill et al 2002). Additionally, stock enhancement en ables the possibility to manipulate the population stru cture of a fish stock (Lorenzen et al. 1997). Differing stock enhancement systems are used for example to increase catch rates, mitigate the effects of fishing, and rebuild depleted fisheries (Lorenz en et al. 2010 ; 2012 ). Across North America multiple species have been stocked to supplement natural populations in an effort to increase catch rates, satisfy high political or social pressures, expand or diversify angler opportunities, and for restoratio n efforts (Li et al. 1996; Shaner 1996; Heidin ger and Brooks 1998 ; Margenau 1999; Jennings et al. 2005; Wills 2006; Ruggerone 2010, Lantry et al. 2011). Catchability or vulnerability to angling is generally thought to be a product of an ral level of aggression ( Bryan and Larkin 1972 ) Though a number of early evaluations report a difference in catchability between individual bass and fished and u nfished populations ( Anderson and Heman 1969 ; Hackney and Linkous 1978 ) researchers only recently investigated vulnerability to angling as a heritable trait. Recent research implicates the ef fects of recreational fishing pressure, angling harvest, and catch and release practices on wild fish populations are possibly unintentionally contribu ting to declined stock catchability (Cooke et al. 2002; Arlinghaus et al. 2007; Philipp et al. 2009; van Poorten 2013). Garrett (2002 ) tested selective breeding in bass to determine if angling vulnerability is a predictable, heritable component. Wild bass caught three or more times were separated from bass not caught. Spawning was
74 conducted through two generations of the vulnerable an d un vulnerable populations then fished. The second generation bass bred for high vulnerability were likely to be caught multiple times compared to the un vulnerable bred bass, suggesting an Philipp et al. (2009 ) showed after three generations (F 1 F 2, and F 3 ) of hatchery stocked high and low vulnerability bred largemouth bass, catchability comprised a genetic heritability of 0.146 (r 2 = 0.995) for F 3 offspring, i ndicating that vulnerability of largemouth bass to angling was a heritable trait. The annual exploitation rates of recreational fisheries can range from < 10% to > 80% and carry the same negative potential as commercial over fishing ( Allen et al. 1998 ; Lewin et al. 2006 ) Fisheries managers successfu lly develop harvest and restricted length regulations to maintain catch rates and reduce ex ploitation (Allen et al. 2013; v an Poorten 2013), while stocking creates new opportunities or enhances pre existing fisheries. The effects of stocking bass into lak es with pre existing predator populatio ns have reported mixed results (Paragamian 1982) and can unintentionally increase fishing pressure on wild populations (Lorenzen 2008). Released cultured fish have been shown to be more susceptible to fishing gear th an their wild conspecifics in some studies (Mezzera and Largiader 2001). Higher susceptibility to fishing implies higher recapture of stocked fish and reduced potential for genetic mixing of wild and hatchery fish. Specifically of interest for the scope o f this manuscript is the susceptibility of hatchery reared Florida bass > 250 mm to angling Catch per unit effort (CPUE) on a single nave wild bass population over a four week period showed reduced catch rates over cumulative effort for two different l ure types and 75% of the estimated population was caught at least one time (Cole 2014). Angling vulnerabilit y in wild populations
75 differ among species and strains and is not limited to only Largemouth bass (Rieger et al. 1978; Kleinsasser et al. 1990; As key et al. 2006), but is catchability affected by differing hatchery production techniques. Angling vulnerability of different rearing techniques is a relativity un assessed outcome of bass stocking that could potentially have implications for future pro duction and stock enhancement decisions. If the catchability of live reared bass significantly differs from pellet reared bass, stocking recommendations for each group would need re assessment. Significantly reduced catchability was shown between hatcher y (live reared, including minnows) Florida bass compared to Northern bass in two Oklahoma ponds (Rieger et al 1978), but this response could have resulted from behavior differences between these species (Kleinsasser et al. 1990). Suspected intensive (crow ded) production environments of raceways coupled with pellet rearing may increase the likelihood of bass vulnerability to angling if stocked at catchable size (> 250mm TL) as a by product of learned pellet feeding behaviors (Huntingford 2004) Bass in thi s study adhered to standard advanced sized live or pellet reared stocking protocols and stocked in ponds designed to mimic natural central Florida lakes. All bass were allowed 15 months to recruit to angling susceptibility (> 250 mm TL) (Burkett et al. 19 86) to compare vulnerabilities between hatchery reared bas s types. M y study compare d angling vulnerability of Florida Bass originating from three different hatchery rearing treatments. The objective was to assess long term effects of alternative h atchery rearing practices to find if specific production strategies for hatchery reared Florida Bass create differences in angling vulnerability
76 Methods Experimental design consisted of three 0.10 ha ponds stocked with 30 age 1 bass at the Florida Bass Conserva tion Center (FBCC), Webster, FL to directly test comparative angling vulnerability of three treatment groups: Hatchery Forage Hatchery Standard and Hatchery Grade out Hatchery Forage bass represent the closest hatchery reared production product compare d to naturally produced wild bass. These bass were reared in out door ponds on live forage (zooplankton and insect larvae) and never hand fed. The Hatchery Standard treatment represents standard intensively pellet reared hatchery produced bass indoors ha nd fed in concrete raceways. The Hatchery Grade out bass treatment production protocols were identical to the Hatchery Standard treatment, but resulted from a single grading of the entire pellet reared population to cull the larger, faster growing individ uals that cannibalize cohorts (Matthews et al. CH 2 ). All treatments were stocked into forage rich (mainly Lepomid sp. ) ponds for 15 months to obtain adequate size for angling vulnerability. Ponds were stocked with 10 bass > 250 and < 365 mm per treatme nt for a total of 30 bass per pond (300 bass/ha) in July 2014. Stocking in the early morning at reduced pond temperatures of 29.5 0 C and sedation with tricaine methanesulfonate (MS 222) (Tricaine S, Western Chemical, Inc., Ferndale, Washington) attempted t o alleviate additional temperature induced handling stress. Forage, Bluegill Lepomis macrochirus and Redear Lepomis microlophus (40 90 mm TL) stocking rates of approximately 6,000 fish/ha supplied a maintenance diet during the course of the five week s tudy. Bass acclimated to the research ponds for 14 d before fishing. The experiment was conducted over three weeks. Following the last fishing event, the ponds were completely drained, allowing for a census of all surviving fish.
77 The bass originated fr om two indoor 24 m concrete spawning raceways stocked accordingly following out of season Florida bass production protocols from wild broodstock obtained from natural lakes (Matthews and Stout 2013). All bass utilized for this research originated from the same 29 spawns collected October 18 th 20 th 2012 (Matthews et al. Ch. 2 ). The Hatchery Standard (right cheek) and Hatchery Grade out (left cheek) bass were cheek tagged with coded wire tags (CWT) using a Mark IV tagging machine (Northwest Marine Technolo gy Inc. Shaw Island, Washington), and mimicked methods described by Heidinger and Cook (1988). The Hatchery Forage bass were unmarked. Individual lengths (mm TL) and weights (g) were recorded on all 90 bass. The bass in all three treatments were stocked in two, five fish allotments and randomly (random number generator 1 3, Microsoft Excel 2010) assigned to a pond. We did not measure stocking mortality at the onset of the experiment; however, pond census data at the end of the experiment evaluated survi val through the experiment, providing inference regarding stocking mortality. Presence of all bass was established at the end of the study by adding the number of marked caught bass to the unmarked non caught bass. Missing unmarked bass at harvest repres ents possible, but unconfirmed lose due to stocking mortality. A single angler fished equal amounts of time per event in each pond between the hours of 5:30 to 8:30 PM 10 times for three consecutive weeks in August 2014. Individual fishing events rang ed from 30 to 60 minutes. Pond order fished was randomly selected at each fishing event. A single hard bait lure (Bass Pro Shops XPS Floating Minnow, Model: LEML 09) used as a fast retrieve rattle or slow twitch bait simulated active swimming or wounde d live forage. The 86
78 uced mortality. At capture, each bass was mildly sedated in a 19 liter containe r with MS 222 at 25 mg/L to allow easier hook removal and work up. Treatments were identified by microwire tags with a CWT reader, lengths and weights recorded, and the caudal fin received a hole punch at each capture to identify capture and re captures. Hooking mortality estimated at the completion of the experiment compared the known number of angled bass per treatment to the number collected at harvest. Stocking mortality was estimated by combining the non caught bass with accounted for caught bass pe r treatment. Unistat version 6.0, UNISTAT Ltd. and Microsoft Excel 2010, Microsoft Corporation statistical software programs generated all analysis, figures, and tables. Differences in initial size (mm TL) at stocking (unfished) and the total recorded size s of bass caught (fished), including re captures, between treatments were analyzed using General Linear Mixed Model (GL M M) tests, and pair wise comparisons were evaluated A randomized compl ete adjust for pond effects across the three replicates. Box/whisker and dot plots illustrated and compared the combined size distribution of each treatment initially s tock ed (unfished) and the size of captures (fi shed) including recaptures to examine unintentional bias directly related to lure choice Catchability Analysis I evaluated catch per unit effort (CPUE) per hour and per event (not accounting for different lengths of fishing events) Catchability (q = U/N) was modeled as follows. I
79 assume that catchability at the start of fishing, when fish are nave to fishing gear, is q f under regularly fished conditions, events: q i = q f ki where i is the number of prior fishing events experienced (i=0,n). The model was fitted to c atch histories of each bass treatment and pond (three replicat es per treatment ) using the method of maximum likelihood with a Poisson likelihood function. Several nested catchability models of differing complexity were tested including models ing catchability model assuming a shared set of parameters for all fish types or allowing one or more parameters to differ among fish types. Model selection was carried out using the Akaike information criterion (AIC) (Burnham and Anderson 2002) A second method to assess vulnerability between treatments compared the cumulative time required to catch 50% (not including re captures) of the individual bass per treatment. Observations between treatments compared the ratios of cumulative hours required to cat ch 50% (half capture time) of the bass in each treatment as described by Philipp et al. (2009). A significance level of 0.05 was used in all statistical tests. Results Mean total length differed among treatments at the onset of the experiment ( F (2,8) = 93.4; P = 0.0004 ; Table 3 1) D revealed the 298.5 mm (27.6) mean (SD) Hatchery Grade out bass were signif icantly larger than the 275.0 (20.8) mm ( P = 0.001) and 270.3 (17.1) mm ( P = 0.0005) Hatchery Forage and Hatchery Standard
80 treatments, respectively. Differences between Hatchery Forage and Hatchery Standard treatment lengths ( P = 0.20) were not found. St ocking mortality was estima ted at 0% in two ponds and 3% (single mortality ) in Pond 3. A single Hatchery Grade out bass was never caught (marked with a hole punch) or accounted for as a non captured (unmarked) bass at harvest ( Table 3 1 ). The remaining seven marked bass unaccounted for at harvest represented maximum (but unc onfirmed) fishing mortalities or 10% in Pond 3 and 6.6% in Ponds 2 and 5. Since no definite confirmation to the losses of these bass occurred and the losses were approximately equal across treatments, all analyses assumed equal populations during trials Unfished and fished ( includes all r e captures) populations pooled together by individual treatment compared angling vulnerability by length to lure type ( Table 3 1 and Figure 3 1) No significant differences in lengths were found between any of the three unfished and their respective fished treatment populations ( 0.05), but the Hatchery Forage (fished) bass Box/w hisker dot plot showed a large amount of small sized fish captur ed than shown in the original population (Figure 3 1). This was attributed to 10 of the 13 re captured bass lengths measured below the 275.0 mm pooled mean. An average 16 % of the total bass in each pond were never caught by hook and line. Cumulative fi shing pressure per pond equa led 465 m inutes, 7.75 h, or averaged 25.8 hr/ha/week ( Table 3 1 ). The 300 bass per ha density was higher than mark recapture population estimates reported across natural Florida lake s (Hoyer and Canfield 1996), and the 25.8 h w eekly effort per ha was up to five times greater than actual recorded effort s on natural lakes (high end) from creel surveys (Creel surveys, Florida Fish and wildlife Conservation Commission (FWC), unpublished long term
81 monitoring LT M data ). Cumulative catch per angler h ou r was calculated by treatment progressively for each of the 10 angling trips Cumulative m ean catch rates between hatchery reared Hatchery Forage Hatchery Standard and Hatchery Grade out bass treatments were not s ignificantly different ( F (2,8) = 2.579; P = 0.191) after three weeks of fishing pressure, 1.68, 1.33, and 1.46 bass/h r, respectively ( Table 3 1 ). Examination of catch rates pe r hour and per event showed that catch rates per hour were negatively correlated with the length of the fishing event (30 60 minutes), while catch rates per event were largely independent of the length of the event (Figures 3 2 and 3 3) This suggests that bass that are vulnerable to capture tend to be captured early on in the fishi ng event and that longer periods of fishing do not yield proportionately greater catches. It was therefore decided to analyze catches per event rather than per hour. Model selection identified the constant catchability model with equal catchability for all fish types as the most parsimonious, followed relatively closely ( the variable catchability model with all parameters shared among the fish types (Table 3 2) All models allowing parameters to vary among fish types performed substantially differences in catchability among the three fish types. The Hatchery Forage and Hatchery Grade out treatments experienced higher initial catch rates compared to the Hatchery Standard bass during the f i rst two fishing events but were more similar across t reatments in the remaining eight fishing events (Figure 3 3) Similarly, the cumulative ang ling time required to catch 50% of bass in each treatment per pond (no re captures) showed no significant difference in initial catchability among treatments ( F ( 2,8) = 1.408; P = 0.3445) (Table 3 3 ).
82 Observationally, the lower mean 105 minutes required to catch 50% of the Hatchery Forage populations possibly suggests initial higher vulnerability L arge standard deviations between only three replicates and the 93 to 243 min ute 95% confidence interval help explain the lack of non significance. Discussion The initial significant larger mean size, approximately 25 30 mm, of the Hatchery Grade out bass showed no significant increase or decrease in catchability f or the treatment based on lure choice First time individual captures accounted for 24 of 30 Hatchery Grade out bass similarly compared to the 23 and 27 bass captured from the Hatchery Standard and Hatchery Forage treatments. Angling results from two Sou th Dakota impoundments containing 84 (public access; fished) and 887 (private, the specified populations in four days and a single day, respectively (Lindgren and Willis 19 90). Both lakes contained smaller bass, but angling is inefficient for capturing sub stock (< 200 mm) largemouth bass (Anderson and Gutreuter 1983; Gabelhouse and Willis 1986; Lindgren and Willis 1990). Relative stock density (RSD) relationships show 200 + mm bass were vulnerable to anglers, but possibly not to the extent of slightly larger 300 mm bass (Gabelhouse and Willis 1986). Artificial lure size selection appeared acceptable to all bass in the study negating unintentional biased angling data re sulting from incorrect lure size. General catchability trends show tendencies that smaller bass are less susceptible to angling due to size and possibly lure size fished (Burkett et al. 1986 ; Wilde et al. 2003). Burkett et al. (1986) reported 91.1% vulne rability of 255 356 mm bass opposed to 58.6% vulnerability of 201 254 mm bass from a single Illinois lake. Wilde et al. (2003)
83 recorded no significant differences in vulnerability to the same minnow shaped lure at sizes 70 and 89 mm by catch rate for This provided independent support for the 86 mm active minnow lure chosen as acceptable for all bass in our study. Based on these results the 250 365 mm bass (281 mm mean) in our angling study were adequately vulnerable to angling and the larger sized Hatchery Grade out bass treatment did not significantly influence catch rate outcomes. The mean Hatchery Forage Hatchery Standard and Hatchery Grade out treatment vulnerability of Florida bass in our three 0.1 ha ponds, 90%, 77%, and 83%, respectively were higher than vulnerabilities recorded from same size Oklahoma hatchery ponds stocked with forage reared age 1 and age 2 Florida bass 58.3% (Reiger et al. 1978). Additionally, the Oklahoma ponds were fished with li ve bait and two different artificial lures. Lure size, not color, significantly impacts catchability depending on bass size, but offering alternate baits types moderates learned lure avoidance potentially increasing over all ca tch rates ( Wilde et al. 200 3 ; Cole 2014). Considering that both pellet reared treatments were removed from artificial feed to foraging on natural prey for 15 months prior to this study, it is believed that a lure mimicking natural prey would not significantly favor a specific treat ment. The initial high catch rates of the Hatchery Forage and Hatchery Grade out bass treatments quickly dropped after the first two fishing events. This seemingly higher initial vulnerability was likely the result of short fishing periods in the firs t two (30 minutes/pond in each fished event) events in combination with nave unfished bass populations. In two of the three ponds, bass were cau ght on almost every cast. Data collection possibly ended before each individual bass in the pond had the chan ce to be
84 captured. Data collection from each captured bass reduced time spent fishing and possibly influenced early treatment catch rates as well The final eight fishing events showed respectively similar catch ra tes between all three treatments as fis hing longer periods of time did not increase catches This most likely is a product of the very small pond sizes and may not be as applicable in larger systems. Philipp et al. (2009) showed angling vulnerability is a heritable trait and could potentiall y explain catchability differences between hatchery stocked lakes or even consistently heavily fished water bodies if either consists of a majority of low vulnerability spawning stock contribut ing to year classes. This could also potentially explain obser ved initial higher catchabil i ties between our bass treatments E ven though all the bass originated from the same 29 spawns the parental contribution combinations of the 30 bass per treatment likely differ between treatments and were unknown Understand ing that the vulnerability predisposition of our broodstock and the offspring utilized in our trials remains unknown, mean percentage of non captured Hatchery Standard bass, 23%, at harvest was higher than the Hatchery Forage and Hatchery Grade out treatme nts, 10% and 14 %. Individual bass vulnerability to angling is difficult to assess and is impacted by gene tic, learned and biological factors. Our data support s previous reports that small portion s of fish populations remain invulnerable to angling as appr oximately 16 % of combined bass treatments harvested after fishing were never angled (Cox and Walters 2002 ; Askey et al. 2006). Burkett et al. (1986) demonstrated high and low angling vulnerability comparing individual bass catch rates and reported 15% of the stocked population remained uncaught after four years in an Illinois Lake. Approximately 25% of the estimated Florida bass population in a private, relatively unfished lake remained
85 uncaught in a four wee k fishing study (Cole 2014). Lure avoidan ce to our active lure was quickly learned and clearly showed by the 34% single re captures and only 3 bass re captured twice. Similar active lure learned avoidance occurred in a natural Florida lake with only two single re captures in a f our week angling study (Cole 2014). Anderson and Heman (1969) reported a 75% and 80% reduced catchabil i ty in 0.2 ha ponds that compared co habituated fished and unfished b ass (230 300 mm group and 300 + mm group). This study focused on hook and line vulnerability diff erences related to hatchery rearing technique and less concerned with cultured versus wild angling susceptibility. Hatchery reared bass may be more susceptible to fishing gear as Mezzera and Largiader (2001) showed in a lake stocked with brown trout Salmo trutta. The 1.49 bass/hr mean combined CPUE obtained from my three bass treatments was higher than the 0.67 bass/hr combined CUPE obtained in a nave bass population (Cole 2014). Additionally, 37% of the hatchery bass were re captured at least one time over the three week angling period compared to 10% of the nave bass over a four week period (Cole 2014). Population density differences and lake size aside, inadvertent behavior changes encouraging riskier or more aggressive foraging behavior could manif est in higher angling vulnerability (Johnsson et al 1996) and possibly explain our elevated re captures compared to the unfished, nave bass population. The elevated effort per ha should also be considered a plausible explanation for the elevated re captu re rate. Comparisons between my catch rates and creel data from natural lakes need to be tempered as density, species comparison (Florida vs. Northern bass), imposed fishing regulations, size structure, angler skill, bait preference, and angling pressure need
86 consideration when comparing catch rates ( Paragamian 1982 ; Garret 2002 ; Allen et al. 2003; Cole 2014 ; Ward et al. 2014). Our study examined the catchability of three treatments of hatchery reared bass in order to determine if the effect of being hatche ry reared persisted at recruitment and manifested into differences in angling vulnerability. Catch per unit effort is commonly used to assess recreational fishery status as the units of measure, cumulative fish/h r or fish/ha, allow for direct comparison a cross differing systems and time frames (Ward et al. 2013). My results show that catchabil i ty of recruitment sized live or pellet reared hatchery bass was not contingent on rearing technique between these specific treatments. Catch rate comparisons to w ild hatched age 1 to age 2 bass, 0.24 to 1.81 bass <457 mm/hr (creel surveys, FWC unpublished LTM data) imply similarity, bu t we caution to view skeptically for reasons mentioned earlier. It is important to consider the data reported in this manuscript re presented advanced fingerling bass stocked in simulated natural systems for 15 months, comparable to standard stock procedures, allowing acclimation and growth before recruitment to angling. Stocking larger sized sub adult bass immediately susceptible to angling may elicit different results. Implications for Management Angling based implications for stocking any of the three types of hatc hery reared bass examined in my study typically center on angler catch rate satisfaction. Stocking sub adult or adva nced fingerling bass can effectively increase catch r ates (Buynak and Mitchell 1999; Buynak et al. 1999), but increases are short lived unless stocking is continued annually. Urban fisheries and or small systems could potentially benefit from stocking sub adult or advance sized hatchery bass to maintain adequate catch rates as
87 elevated fishi ng pressure or inability properly manage these often degraded systems negate other management strategies. Stocking selected systems to create or increase ishery with Hatchery Grade out bass needs further research before implementing and requires consideration for potential long term population effects if population diversity of the system is of direct concern (Maceina et al. 1988) Stocking forage or pelle t reared first generation offspring from wild caught bass broodstock show equivalent vulnerability to angling. Either could be successfully utilized in future enhancement projects targeting catch rate outcomes.
88 Table 3 1. Initial number s of Hatchery Fo rage Hatchery Standard and Hatchery Grade out bass stocked in three 0.10 ha ponds, mean length and treatment mean (SD) in mm, total cumulative time fished (min ), hours fished per hectare per week, and cumulative pond and treatment mean (SD ) CPUE after 10 fishing events. Capture data details individuals and treatment totals caught, total captures, number of single bass re capture s, double re captures, non captured bass at harvest, and remaining bass per treatment per pond at harvest. Individuals were a ccounted for by adding the Captured and Non captured bass numbers. Numbers not adding to 10 indicated missing bass. Hatchery Forage Hatchery Standard Hatchery Grade out Pond 2 Pond 3 Pond 5 Mean (SD) Pond 2 Pond 3 Pond 5 Mean (SD) Pond 2 Pond 3 Pond 5 Mean (SD) Initial (N) 10 10 10 n/a 10 10 10 n/a 10 10 10 n/a Mean length, mm 274.5 271.0 279.5 275.0(20.8) a 268.0 268.5 274.5 270.3(17.1) a 302.0 294.0 299.5 298.5(27.6) b Time Fished, min 465.0 465.0 465.0 n /a 465.0 465.0 465.0 n/a 465.0 465.0 465.0 n/a Fished, hr/ha/week 25.8 25.8 25.8 n/a 25.8 25.8 25.8 n/a 25.8 25.8 25.8 n/a CUPE fish/hr 1.68 1.42 1.94 1.68(0.26) a 1.29 1.42 1.29 1.33(0.08) a 1.42 1.55 1.42 1.46(0.08) a Capture d ata Hatchery Forage Hatchery Standard Hatchery Grade out Pond 2 Pond 3 Pond 5 Total Pond 2 Pond 3 Pond 5 Total Pond 2 Pond 3 Pond 5 Total Captured 9 of 10 8 of 10 10 of 10 27 of 30 8 of 10 7 of 10 8 of 10 23 of 30 8 of 10 8 of 10 8 of 10 24 of 30 Total Captures 13 11 16 40 10 12 10 32 11 12 12 35 Re captures 4 3 5 12 2 4 2 8 3 4 3 10 Re captures, x2 0 0 1 1 0 1 0 1 0 0 1 1 Non captured 1 2 0 3 2 3 2 7 2 1* 2 5 Recover ed (N) 9 8 10 27** 10 9 9 28** 9 9 9 27** Different superscript a b letters denote significant differences between treatments. A single Pond 3 Hatchery Grade out bass was unaccounted for by capture or at harvest and was attributed to stocking mortality. ** The remaining seven ba ss captured at least one time, but not accounted for at harvest, were attributed to fishing or natural mortality.
89 Table 3 2 Model selection using Akaike information criterion (AIC) for alternative catchability models. Model Model # Parameters L AIC C(qf) Model 1 2 116.34 120.34 0 C(qfj) Model 2 4 115.88 123.88 3.54 Model 3 4 112.92 120.92 0.58 Model 4 6 111.64 123.64 3.3 Model 5 6 112.75 124.75 4.41 Model 6 6 112.79 124.79 4.45 C(qf Model 7 10 111.57 131.57 11.23
90 Table 3 3 Cumulative fishing time (min) required to capture (not counting re captures) 50% of each treatment per pond and treatment mean ( SD) indicated vulnerability to first time capture between treatmen ts. Half capture time, min Pond (N) Hatchery Forage Hatchery Standard Hatchery Grade out Pond 2 (30) 60 180 60 Pond 3 (30) 225 225 225 Pond 5 (30) 30 225 285 Mean (SD) 105 (105.0) a 210 (26.0) a 190 (116.5) a Different superscript a letters denote significant differences between treatments.
91 Figure 3 1. Comparison of Hatchery Forage A), Hatchery Standard B), and Hatchery Grade out C) initial unfished and cumulative fished (caught hook and line) bass treatment populations by length (mm). The line in the box shows the median and the small hash line represents the mean. The boxes show the interquartile range and the whiskers represent 1.5 times the interquartile range. Dots past the end of the whiskers are outliers. The dot plots depict the actual measured lengths of the bass and the three bars represent the mean (center, with black dot) and standard error. A B
92 Figure 3 1 Continued C
93 Figure 3 2 Calculated catch rates per hour plotted by actual angling duration for each bass treatment. 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 Catch rate per hour Angling duration Hatchery Forage Hatchery Standard Hatchery Grade-out
94 Figure 3 3. Average catch rates per event plotted by angling duration for each bass treatment. 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 Catch rate per event (numbers) Angling duration Hatchery Forage Hatchery Standard Hatchery Grade-out
95 Figure 3 4. Average catch per event (from the three replicates) and best performing AIC models. Model 1 (most parsimonious) represents constant catchability with equal catchability among bass treatments and Model 3 represents a variable catchability model with all parameters shared among bass treatments. 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 0 2 4 6 8 10 Catch per event (numbers) Fishing event Hatchery Forage Hatchery Standard Hatchery Grade-out Model 1 Model 3
96 CHAPTER 4 SIZE AND D ENSITY DEPENDENT PROCESSES POST RELEASE AND THEIR IM PLICATIONS FOR OPTIMAL RELEASE STRATEGIES It is important for fisheries ma nagers to examine early size and density dependent processes in natural water bodies in order to establish optimal release strategies. Stocking fish of the correct size and densit y should help re create a fishery, but naturally occurring density dependent processes observed in fish recruitment require consideration in selecting fish size, stocking density, and when stocking is most beneficial (Lorenzen et al. 2010). Parkos and Wah l (2002) reviewed recruitment mechanisms for age 0 LMB and reported diet, hatch date, and prey availability greatly affected growth and influenced survival. Additionally, stock recruitment relationships were not correlated with successful spawns from incr easing adult spawning stock abundance and shown not to directly influence year class strength (Allen et al. 2011). There are theories and documented evidence to support multiple density dependent processes acting on different life history stages in year cl ass regulation (Hazlerigg et al. 2012). These multiple interacting factors include season forage availability, survival and growth processes influenced by both and size and density of natural bass populations Seasonal factors s pecifically based on te mperature gradients i n differing latitudes, suggest first spawns have a greater survival advantage compared to later spawns ( Goodgame and Miranda 1993 ; Pine et al. 2000 ) The earlier hatched bass fry gain a size advantage over the later spawned Lepomid sp ecies Their diets shift to piscivory earlier increasing size obtained by first winter possibly increasing survival and recruitment ( Phillips et al. 1995 ; Olson 1996 ; Matthews et al. Chapter 2 ). The density
97 depen de nt interactions of increasing age 0 juv enile abundance can reduce first year growth by competition causing increased over winter starvation in higher latitudes and increased predation in lower latitudes affecting year class strength (De Angelis et al. 1991 ; Parkos and Wahl 2010 ). Intra cohort cannibalism can influence growth and survival of age 0 LMB in more southern ranges due to elongated spawning seasons (Johnson and Post 1996), but shorter spawning durations diminish size advantages between spawning events decreasing loss from cohort cannib alism. Accounting for these processes in corrective stocking projects could potentially increase stocking contribution and year class strength but still may not be truly additive concerning abundance or significantly increase population numbers Densit y depende nt growth relates to intra specific food competition between individuals in the same population (Rose et al. 2001). Increased density of individuals requiring similar sized food items increases competition and can reduce prey items resulting in r educed growth rates. Persistent reduced growth rates can cause size selecti ve mortality in age 0 fingerling populations possibly reducing recruitment to the year class. Elevating an age class density over carrying capacity by stocking will limit resource s for both wild and hatchery fish increasing mortality, likely negating enhancement success. De Angelis et al. (1991) reported increased Smallmouth Bass Micropterus dolomieui fry numbers stunted growth and severely reduced prey numbers ultimately increasi ng winter mortality. Prey availability was an important factor in the first year survival in stocking three sizes (6, 46, and 100 mm) of Walleye Stizostedion vitreum in reservoirs (Hoxmeier et al. 2006). Studies examin ing first year growth and largemouth b ass Micropterus salmoides survival to age 1 from stocked ponds and
98 natural settings indicated length obtained by winter greatly influences recruitment probability (Gutreuter and Anderson 1985; Garvey et al. 1998). Larval bass to early juvenile fingerli ngs incur higher density dependent mortality, but population density dependent mortality effects shifts to more growth dependence as fish reach 25% of their maximum length (Lorenzen and Enberg 2001; Hazlerigg et al. 2012). Det ecting density depende nt mort ality from field data is difficult and should not be confused with recruitment limitation as the former could lead to natural compensatory population responses and the latter lead to depensatory responses possibly requiring corrective management action (Ro se et al. 2001). Stocking in an attempt to influence greater numbers of fish, specifically Florida Largemouth Bass Micropterus floridanus recruitment needs to account for these interacting factors and realistic carrying capacity of each individual site s tocked for appropriate bass size and density to achieve goals and maximize stocking resources. Substituting hatchery fish stocking date for a pre determined natural early life event (hatching or ontogenetic niche shift) (Olson 1996 ; Ludsin and DeVries 19 97 ) may provide information for better use of hatchery bass Reviewing past decisions considering bass size at stocking and numbers stocked favored stocking larger bass (Loska 1982), but integrating advances in the understanding of first year recruitment in natural bass populations and improved bass production techniques call for re assessment of stocking fingerlings on an individual project based level (Ludsin and DeVries 1997; Parkos and Wahl 2002 ; Parkos and Wahl 2010; Horne and Lochmann 2010; Csargo et al. 2013; Matthews and Stout 2013) We attempt to simulate possible results a fter stocking four sizes of bass at four densities in experimental ponds
99 designed to reflect a newly restored system containing no bass, to explore how these interacting factor s could influence stocking success and recruitment. We examined sur vival and growth effects of bass stocked at four increasing densities and sizes in earthen ponds by quantifying density dependent survival and growth over 30 days The experimental design was modeled from laboratory trials concerning density dependence in growth and mortality of Zebrafish, Danio rerio (Hazlerigg et al. 2012). Population densities were derived from 12 natural bass population values for assessment and later comparison back to natural systems (Parkos and Wahl 2010). We hypothesize that stocking succes s depends more on timing combined with stocking size and density and predict higher short term survival for larger stocked bass, but long term survival and age 1 recruitment ma y show stronger dependence on stocked and pre existing densities then initial stocking size of fingerling Analyses simply compared mortality and growth of hatchery bass stocked to mimic natural populations to observe potential effects of natural recruitm ent process and possibly provide insight for future projects debating stocking size and density. Methods Trials conducted in four 0.08 ha (809 m 2 ) ponds at the Florida Bass Conservation Center (FBCC), Webst er, FL utilized live reared Florida bass Four g radually increasing size classes 30, 40, 60, and 90 mm at four different densities were examined one at a time. Each of the four ponds was randomly assigned a bass density and stocked with equal sized bass at 1, 4, 7, or 10 bass fingerlings/m 2 based on t he range of mean peak age 0 densities from 12 lakes in Illinois (Parkos and Wahl 2010) ( Table 4 1 Figure 4 1). Ponds were stocked according to appropriate time frames based on hatchery bass size to mimic post hatch size and time intervals expected in na tural age 0 bass
100 populations ( Table 4 1 ). Forage size and item diversity departed from expected natural food item availability in the 60 mm (June) and 90 mm (August) trials to maintain more consistent pond conditions across all trials. The total number o f bass required per trial was approximately 18,000 fingerlings. Bass harvested at the end of each trial were not reused in subsequent trials. Live reared bass fry stocked at 196,000/ha yield approximately 117,600, 30 to 40 mm bass fingerlings/ha in 30 da ys at the FBCC and supplied bass required for the 30 and 40 mm trials. The 60 and 90 mm trials required restocking 30 to 40 mm fingerling bass at lower densities of 98,000 and 19,700 fingerling s /ha t o achieve required sizes on natural non supplemented foo d supplies. Pre stock initial length (mm), weight (g), and condition factor (K) of 100 individuals were collected for performance comparisons at har vest Total weight and approx imate number were listed in Table 4 1 The four ponds were filled with age d well water and fertilized to promote zooplankton production 10 to 14 d before stocking (Coyle et al. 2012; Ludwig 2012). Fertilization protocols were repeated for each of the four trials. No additional forage or fertilizer was utilized during our trial s. The ponds additi onal certainty to filter out unwanted Centrarchid and Lepomid fry. No predators were stocked removing the inter cohort predation variable allowing f or direct measurements of survival and growth across stocking size and density This data at best represents best case survival in new systems and survival in lakes with pre existing predators likely more variable. Standard water quality parameters were monitored, but only reported if responsi ble for an adverse effect on my study data.
101 Harvest occurred 30 days post stock in all trials Total weight and number (app roximated by weight), population mean length and weight, survival, and final density in m 2 were recorded. One hundred individual lengths and weights were collected from each harvested pond for comparisons. Measured f ish were sedated with t ricaine m ethanesulfonate (Tricaine S, Western Chemical, Inc., Ferndale, Washington) for safe handling and to reduce stress related disease outbreaks commonly induced by seine harvesting. Analyses consisted of comparing initial average total length and stocking density to final average total length at final density 30 d post stock. The data was plotted on a single graph with total length on the y axis and density of the x axis. A line connected initial length at stoc king density to final length at harvest density. The vertical increase of the line (from right to left) represents growth and the horizontal le ngth depicts decreased density and illustrates mortality The x axis scale was manually manipulated to account for all density results requiring unequal scaling. Condition factors (K) provide comparable data on relative population fitness at stocking and harvest to possibly identify the shift from density dependent mortality to density depende nt growth, if present. The numeric K value relates harvest condition back to the initial condition of the stocked population for each of the four lengths evaluated and used as an index for evaluating growth between stocking densities implying food resource availability Data analysis utilized Unistat version 6.0, UNISTAT Ltd. and Microsoft Excel 2010, Microsoft Corporation statistical software programs. Results A ssessment from the combined data collected in experimental, predator free hatchery ponds revealed stocking density influenced mortality greater as density
102 increased fo r bass stocked at 30 and 40 mm. Both density depende nt mortality and growth effects were displayed in the 60 and 90 mm size classes ( Table 4 2 Figures 4 1 and 4 2 ). Food availability was not controlled in the ponds. Condition factors provided evidence that food type and quantity reduced K values as bass increased in stock size and density compared to initial population K values at stocking ( Table 4 3 ). Overall general trends suggest stocking density contributed to mortality greater in the 30 and 40 mm size classes based on recorded weight and length increases Density depend e nt growth wa s apparent as stocking density increased in all sizes displaying greater influence as stocking size increased. The 60 and 90 mm bass data exhibited higher mortality and reduced growth, comparably, suggesting food type and quantity confounded the results ( Table 4 2 ). The combined d ata from all four trials showed reduced 30 mm bass survival from 98.3% to 62.3% stocked at 1/m 2 to 4/m 2 Comparing 30 mm bass survival at densities of 4, 7, and 10/m 2 revealed negligible survival difference, but all three illus trated reduced growth in length and weight compared to the 1/m 2 density ( Table 4 2 Figures 4 3 and 4 4 ). Survival was slightly more consistent across the four densities for the 40 mm bass and showed similar reduced growth as density increased with the hi ghest survival reported at the 10/m 2 density, 80.5% respectively. Competition for food items reducing both growth and possibly cannibalism was the suspected cause of this increased survival based on mean SD of 50.7 3.6 mm (range 44 72 mm) and K val ues (Tables 4 2 and 4 3). The reduced survival in the 60 and 90 mm bass trials was initially unexpected considering current generalized understanding of expected higher survival in larger size bass. This possibly indicated a lack of forage or the right s ize and
103 type of forage. The 7 and 10/m 2 90 mm data provided evidence for this. Large populations of free swimming crustacean Ostracods (undetermined Ostracoda sp.) were noted in these two ponds at stocking. The increase in forage possibly elevated the s urvival of the two highest stocking densities over the lower densities and accounted for the only instance of a final harvest biomass of an initially lower stocking density, 7/m 2 39.27 kg, to exceed a high er stocked density, 10/m 2 33.66 kg ( Table 4 2 ). The 90 mm bass stocked at 7/m 2 also experienced the greatest average length increase, 11.7 mm, compared to the other three densities stocked with 90 mm bass over the 30 d period (Figure 4 4). This provided evidence that the lower survival of the larger si zed bass was potentially impacted by inadequate forage items. Trends in mean population length increases after 30 d in the ponds illustrated approximately 0.4 mm/d or greater growth rates in each of the four stocking densities at 30 mm and 40 mm except at 10/m 2 density (Figure 4 4 ). The data from the 60 and 90 mm bass trials depicted strong density depende nt growth influences, but results need to be tempered against the la ck of adequate food item sizes. Increases in average bass weight decreased as ini t ial stocking size increased with 60 and 90 mm bass stocked at 4, 7, and 10/m 2 experiencing erratic gains supplying additional support for density depende nt growth and mortality process on age 0 bass. Viewing the average mean harvest lengths for each size group across the four increasing stocking densities showed 30 and 40 mm bass stocked to mimic post hatch size and time intervals expected in natural age 0 bass populations in central Florida proved effective for stocking, presenting adequate growth a nd sur vival after 30 d (Figure 4 5 ). The lack of growth and corresponding reduced survival in the 60 and 90 mm bass demonstrated the
104 need to stock larger bass when ample larger food items are available. Results support redu cing stocking densities as bass stoc ked size increases to prevent additional increased density dependent growth constraints. This needs further research to verify as our results did not include growth and survival data to age 1 recruitment. Discussion This study illustrates the need to un derstand the interactions of stocking size, density, and timing can have on recruitment in systems devoid of natural bass populations Stocking 30 to 40 mm fingerlings in early spring may be equally successful as stocking 90 mm advanced fingerling s in lat e spring at similar latitudes. Revi ewing results from stocking Florida bass fingerlings (TL = 38 mm 2.2) in April and advanced fingerlings (TL = 85 mm 12 mm) in June in the same recently renovated lake in southern Florida showed the smaller fingerling s were equal in size and contribution compared to the advanced fingerling s one year post stock (Matthews et al. Unpublished report ). In contrast, the ability to produce and stock multiple sizes of bass may promote recruitment success at more northern and southern latitudes from the hatchery origin by allowing stocked fish more time to grow prior to first winter in systems with pre existing bass populations Size dependent over winter mortality strongly influences first year LMB recruit ment at intermediate latitudes ( Miranda and Hubbard 1994 ; Ludsin and DeVries 1997 ; Pine et al. 2000 ) with moderated influences in northern and southern latitudes ( Garvey et al 1998 ; Rogers and Allen 2009). This same pattern of size dependent over winte r mortality could relat e to bass recruitment under a smaller spatial scale with central Florida equating the intermediate LMB latitudes. Six 0.26 ha hatchery ponds stocked with equal numbers of thre e different bass cohorts originating from 29 spawns evaluated survival one year post stock. Over winter size selective mortality
105 was evident between 6 months (September) and 12 months (March) post stock evaluati ons and revealed the bass population averaging 176 mm by fall experienced significantly less mortality than the other two co horts averaging 156 and 152 mm. Condition factors (K) were significa ntly greater for the 176 mm cohort post winter harvested in March (Matthews et al. Chapter 2 ). The mean population daily growth of the 30 and 40 mm sized bass in our study were compar able to growth rates reported form southern latitude natu ral systems for similar aged bass (35 49 d post hatch) with the exception of reduced growth in the 40 mm bass stocked at 10/m 2 ( Phillips et al. 1995 ; Rogers and Allen 2009 ). Conversely, the 60 and 90 mm bass populations experienced redu ced daily growth compared to bass in a southern reservoir of similar age (75 150 d post hatch) (Jackson and Noble 2000). Pre stocking conditions in all 16 of the ponds trials were consist ent The lack of includin g fish or comparable sized food item for forage in the ponds demonstrated the effects of stocking adequate ly sized fish based on available forage. The perceived advantage for stocking larger sized bass was possibly negated by the lack of adequate forage r evealing the need for forage assessment in decisions determining stocking size and density. Size selective mortality effects smaller bass possibly leading to starvation or the resulting reduced growth rate extends vulnerability to predation over an elonga ted time frame (Jobling 1993 ; Cargnelli and Gross 1997 ; Garvey et al. 1998 ). The factors influencing recruitment are debated depending on selected criteria with size obtained by first winter and prey item availability commonly viewed as mitiga ting factors in age 0 survival ( Miranda and Hubbard 1994 ; Fullerton et al. 20 00; Hoxmeier et al. 2006 ).
106 Our study demonstrated the need to under stand and account for age 0 bass ontogenetic shifts in life history as th ey pertain to density dependent processes directly effecting stocking effectiveness. Data from the 90 mm trials showed that correct sized forage availability a ff ected survival greater than initial stocking density A documented unexpected Ostracod population in the two higher density ponds demonstrated the effects o f timing stocking on adequate sized forage base with increased survival over the two lower density ponds. S tocking advanced sized fingerling (65 90 mm) on top of a natural Threadfin Shad Dorosoma petenense spawn demonstrated positive resul ts coordinating size and time of stocking to adequate food resources (Mesing et al. 2008). Stocking advanced fingerlings in early spring may negate the potential survival increase of stocking larger bass with respect to latitude differential between hat chery origin and stocking site. We did not expect high mortality resulted from cannibalism in our 30 and 40 mm trials at any density stocked as minimum and maximum size ratios (mm) remained below the 2:1 predator to prey length ratio suggested by Johnso n and Post (1996) a s the maximum item size an age 0 bass of a given length can consume. Still cannibalism may account fo r some level of mortality in these two groups, but our assessments remain unconfirmed as stomach contents were not analyzed. Cannibali sm likely accounted for a larger percentage of mortality in the 60 and 90 mm size groups. Population means and standard deviations paired with predicted maximum predator prey length ratios as high as 3:1 determined from 100 bass sampled at harvest support our conclusion. Predation likely accounts for the unexpected low survivals at the 1/m 2 densities and inversely the increasing densities may reduce cannibalism as growth is
107 reduced due to diminished forage availability. It is interesting to point out the predicted predator to prey length ratio in the 90 mm, 7/m 2 pond (reported the highest survival of all the 60 and 90 mm pond trials) was 1.6:1 indicating the largest bass sampled in the pond was not large enough to consume the smallest recorded bass sample d from the pond. Intra cohort predation is reported to contribute to predator year class formation and this type of regulation may specifically negate the possibility of achieving additive stocking effects where natural recruitment is present (Johnson and Post 1996 ; Lorenzen 2012; Hhn et al. 2014 ). Conversely stocking 100 150 mm minnow reared advanced fingerling LMB at 60/ha produced no negative influence on growth or condition of wild conspecifics, but researchers caution increased stocking densities or higher wild year class strength could negatively influence final year class strength, comparativ ely (Horne and Lochmann 2010). Our one month post stock survivals were not impacted by naturally produced age 0 bass populations or predators but stockin g on top of pre existing populations needs consideration. This data allowed us to view distilled theoretical situations concerning stocking size and density and would have expected much greater mortality and reduced growth as stocking density increased if tested in non manipulated natural systems. Stocking small juveniles with existing populations may not effectively enhance fish stocks as survival is still influenced by density dependent and independent mortality (Lorenzen 2000). Stocking larger juvenil es on pre existing similar naturally produced fish could increase density dependent growth effects increasing competition possibly reducing over all final recruitment to the year class or simply replacing wild recruitment (Leber et al. 1995; Lorenzen et al 2012).
108 Utility for Stocking D ecisions Florida bass recruitment along with other keystone predator populations is strongly impacted by size and density depende nt growth and mortality including intra cohort cannibalism ( Mittelbach et al. 1995 ; Schindler et al. 1997 ; Claessen et al. 2000 ). The demand for maintaining quality recreational fisheries for popular predator species i ncluding but not limited to Florida bass, northern bass Walleye, and Northern Pike results in propagation and stocking large numb ers of fish (Brooks et al. 2002; Neal et al. 2002 ; Diana and Wahl 2009 ; Hhn et al. 2014 ) Extrapolating stocking outcomes from our results initially predicts stocking smaller sized fingerlings could equally contribute to year class recruitment unless nat ural recruitment is greatly impaired by spawning or forage bottlenecks. Brooks et al. (2002) suggested stocking small Walleye fingerlings would generally be more successful based on given stocking rates and cost comparison but stocking advanced fingerli ngs may become more effective if rearing techniqu es and timing of stock improve. Stocking outcomes still need to consider the possible increased mortality of stocking smaller fingerlings as these fish will require longer periods of time to attain recruitm ent size compared to stocking larger fish. Our results in combination with current literature suggest stocking success is dependent on timing stocking with adequate sized forage (Ludsin and DeVries 1997 ; Hoxmeier et al. 2006 ; Mesing et al 2008 ) exist ent age 0 densities (Horne and Lochmann 2010), and hatchery broodstock and spawning technique selection (Hhn et al. 2014). Stock enhancement projects unable to obtain the recommended information should be delayed or stocked with smaller fingerling bass until this information becomes available. This study should be repeated with the addition of fish as a prey item to
109 observe effects on size and density at harvest and gut content analysis to observe shift to piscivory and mortality related to cannibalism. We did not compare bass spawned in the wild rather we simulated natural spawning with the collection of w ild broodstock (60 females: 40 m ales, 3:2 paired ratio in raceways) spawned without manual or hormonal stimulation. Based on this we feel our data represents more natural occurring density dependent results but, still may not be completely free of relaxed natural selection effects and requires additional work comparing fry production in hatchery ponds vs. raceways to confirm. We recommend additional pond studies to examine bass size and density selected as stocking high numbers of larger sized fish may induce negative effects on the year class. We also recommend verifying actual forage recruitment bottlenecks as opposed t o degraded systems reducing bass (> 254 mm) carrying capacities where stocking advanced fingerling is a creditable option. Finally, we recommend using natural recruitment in suggest 1 to 5% surviv al to recruitment or 5 to 15% contribution to a single year class be considered successful and safe concerning loss of genetic diversity when natural recruitment is present ( Heitman et al. 2006 ; Tringali et al 2007 ; Lochmann 2010; Porak et al. 2015 ).
110 Table 4 1. Initial number stocked, individual mean length (mm) and weight (g) from pond reared populations of Florida bass fingerlings, and the total weight stocked (kg) at 30, 40, 60, and 90 mm size classes in randomly assigned 0.08 ha central Flo rida hatchery ponds at 1, 4, 7, and 10 bass/m 2 densities. Standard deviations in length and weight (mean SD) across all four densities for the 30, 40, and 60 mm trials were identical while the bass for the 90 mm trials were produced from two populations and listed at the bottom of the table. Trial time frames were 30 and 40 mm March April, 60 mm June, and 90 mm August. 30mm* Stocking Density, m 2 1 4 7 10 # Stocked 809 3,236 5,663 8,090 Individual, L mm 30.00 30.00 30.00 30.00 Individual, wt. g 0.31 0.31 0.31 0.31 Total wt. STK, kg 0.25 1.0 1.8 2.5 40mm** Stocking Density, m 2 1 4 7 10 # Stocked 809 3,236 5,663 8,090 Individual, L mm 42.26 42.26 42.26 42.26 Individual, wt. g 0.76 0.76 0.76 0.76 Total wt. STK, kg 0.6 2.5 4.3 6.1 60m m*** Stocking Density, m 2 1 4 7 10 # Stocked 809 3,236 5,663 8,090 Individual, L mm 58.3 58.3 58.3 58.3 Individual, wt. g 2.2 2.2 2.2 2.2 Total wt. STK, kg 1.8 7.1 12.5 17.8 90mm**** Stocking Density, m 2 1 4 7 10 # Stocked 809 3,236 5,663 8,0 90 Individual, L mm 84.9 84.9 90.7 90.7 Individual, wt. g 6.41 6.41 8.3 8.3 Total wt. STK, kg 5.2 20.7 47.0 67.1 Standard deviations: *mm 2.3, g 0.07,*mm 2.0, g 0.12, ***mm 4.1, g 0.61, and ****mm 7.0, g 1.8 or mm 5.1, g 1.4.
111 Ta ble 4 2. Total pond harvest weight (kg), total number of bass harvested, individual average length (mm SD) and weight (g SD) at harvest, survival, and final remaining density (bass/m 2 ) from each pond reared population of Florida bass fingerlings stock ed at 30, 40, 60, and 90 mm size classes in randomly assigned 0.08 ha central Florida hatchery ponds at 1, 4, 7, and 10 bass/m 2 densities. 30mm Stocking Density, m 2 1 4 7 10 Total harvest wt. ,kg 2.75 5.43 6.7 9.9 Total # Harvested 795 2,019 3,621 5 ,440 Avg Length, mm 61.8 3.4 58.3 2.8 52.9 2.8 52.4 2.5 Avg wt., g 3.45 0.36 2.69 0.39 1.85 0.33 1.82 0.27 Survival 98.3% 62.3% 63.9% 67.2% Final Density, m 2 0.98 2.5 4.5 6.7 40mm Stocking Density, m 2 1 4 7 10 Total harvest wt. ,kg 2.52 5.04 5.83 8.41 Total # Harvested 582 1,924 3,491 6,050 Avg Length, mm 71.0 4.4 62.3 3.0 55.0 2.0 50.7 3.6 Avg wt., g 4.33 0.9 2.62 0.4 1.67 0.2 1.39 0.4 Survival 71.8% 59.4% 61.6% 80.5% Final Density, m 2 0.72 2.4 4.3 8 60mm Stocking Density, m 2 1 4 7 10 Total harvest wt. ,kg 0.9 4.5 6.91 9.14 Total # Harvested 198 1,607 2,383 2,470 Avg Length, mm 72.8 9.6 63.5 10.7 64.2 7.6 68.1 8.9 Avg wt., g 4.55 2.4 2.8 4.0 2.9 1.9 3.7 2.9 Survival 24.5% 49. 5% 42.0% 30.5% Final Density, m 2 0.2 2.0 2.9 3.1 90mm Stocking Density, m 2 1 4 7 10 Total harvest wt. ,kg 3.65 10.44 39.27 36.66 Total # Harvested 374 1,470 3,705 4,029 Avg Length, mm 94.3 16.9 86.6 14.4 102.4 11.5 94.7 12.2 Avg wt., g 9.4 6.9 7.1 7.4 10.6 3.9 9.1 7.3 Survival 46.0% 45.4% 65.4% 49.8% Final Density, m 2 0.5 1.8 4.6 5.0
112 Table 4 3. Condition factors (K), n = 100, for initial pond reared Florida bass populations produced for stocking 30, 40, 60, and 90 mm siz e classes at 1,4 7, and 10 bass/m 2 densities and the resulting K value from each size class and density harvested 30 days later. Density ( bass/m 2 ) Size Class Initial 1 4 7 10 30 1.14 1.45 1.35 1.24 1.26 40 1.00 1.20 1.08 1.00 1.0 6 60 1.08 1.12 0.97 1.06 1.09 90 1.02*/1.11 1* 0.95* 0.96 0.99 *Dif ferentiates the two initial bass populations utilized to produce the 90 mm size class
113 Figure 4 1. Total average population length and density differences between initial size (mm) at stocking density (m 2 ) and final harvest lengths and densities for Florida bass 30 days post stock ed in 0.08ha ponds The vertical change shows increase in length and the horizontal change illustrates density changes or total mortality. More vertic al lines depict larger size increases and more horizontal lines depict increased mortality. The x axis scale was manually manipulated to account for all density results requiring unequal scaling Each lines begins at one of the four initial starting densit ies (1, 4, 7, or 10 m 2 ) and reads to the left. 0 10 20 30 40 50 60 70 80 90 100 110 Total Length, mm Density, m 2 30 mm 40 mm 60 mm 90 mm
114 Figure 4 2. Results combining each size class by stocking density to compare final density after 30 days post stock The independent variable was stocking density (m 2 ) and the dependent variable was h arvest density (m 2 ). Equivalent values for density at harvest represented 100% survival. All ponds mimicked newly filled or restored systems with no predators. Food items were limited by natural production and thus uncontrolled. No additional food items were fed. 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 1 4 7 10 Final Density, m 2 Stocking Density, m 2 30 mm 40 mm 60 mm 90 mm
115 Figure 4 3. Total final survival of four size classes of age 0 Florida bass stocked at 1, 4, 7, and 10 bass/m 2 in 0.08 ha hatchery ponds in central Florida and harvested 30 days post stock. Results denote density and size dependent mortal ity, but cannibalism and sufficient food item availability needs consideration in interpreting these results. 0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 100.0% 1 4 7 10 Survival %, after 30 days Stocking Density, m 2 30 mm 40 mm 60 mm 90 mm
116 Figure 4 4. Differences between initial and final mean population length s represented average somatic growth in mm 30 days post stock for 30, 40, 60, and 90 mm size class age 0 Florida bass each stocked at four increasing densities. Trends show reduced growth as density and initial stocking size increased 0 5 10 15 20 25 30 35 1 4 7 10 Average Population Growth, mm Stocking Density, m 2 30 mm 40 mm 60 mm 90 mm
117 Figure 4 5. Average individual final length s at harvest of Florida bass per size c lass showing density dependent growth Size increases were reduced as stocking density and initial stock length increased. 30 40 50 60 70 80 90 100 110 1 4 7 10 Average Size at Harvest, mm Stocking Density, m 2 30 mm 40 mm 60 mm 90 mm
118 CHAPTER 5 POST STOCKING ASSESSMENT : EVALUATING FLORIDA LARGEMOUTH BASS SIZE DEPEDENTS ON ELECTROFISHING EFFECTIVENESS IN PONDS. Current Florida Largemouth Bass Micropterus floridanus stocking protocols followed by the Florida Fish and Wildlife Conservation Commission (FWC) include stocking lakes with advanced sized 100 mm fingerling bass into recruitment limited and habitat degrade d systems. Stocking evaluation and the effects of stocking hatchery fish on the pre existing wild bass population is important to refine culture and stocking methods to optimize stocking success (Horne and Lochmann 2010). Selectivity of various sampling methods used in stocking assessments each carry sampling biases that can distort results. For example, Jackson and Noble (1995) reported differences in the catchability of juvenile Largemouth Bass Micropterus salmoides (LMB) with a bag seine, hand held el ectrofisher, and boom mounted, boat electrofisher. Se ining held devices effectively sampled bass lengths sampling method for data collection can unintentionally bias assessments of abund ance and size structure of both wild and stocked fish (Jackson and Noble 1995; Reynolds 1996; Bayley and Austen 2002). Considering gear selectivity for stocked hatchery bass may reveal biases in estimates of abundance, contribution, and survival during th e first year after the hatchery fish are released into a lake. Estimated high mortality values resulting from electrofishing assessments of recruited age 1 bass perceived as hatchery rearing effects could realistically in part be due to sampling bias (Ho rne and Lochmann 2010). Accounting for high variability in natural mortality of bass to age 1, (hatchery reared or wild) also needs consideration in final assessments (Hightower et al. 1982).
119 Multiple sampling techniques and comparisons show different methods are more effective depending on sampling purpose. Boat electrofishing gear commonly selected effectiveness (Tate et al. 2003) and efficacy (Burns and Lantz 1978). U nfortunately, there are a number of documented concerns that catchability is size, species, habitat, and seasonally dependent (Reynolds 1996). Standardizing electrofishing power output substantially reduced some of the catch variation caused by the equipm ent ( Burkhardt and Gutreuter 1995). Evaluations of stocked hatchery bass in Florida mainly occurred within the first year or at one year after initial stocking using boat electrofishing. Studies show catchability with boat electrofishing was less successf ul than other sampling methods concerning small fish (Bayley and Austin 2002), influenced by species and season (Schoenebeck and Hansan 2005), and can be influenced by habitat (Sammons and Bettoli 1999). Boat electrofishing was less effect ive for sampling fingerling bass under 130 mm (Jackson and Noble 1995) and handheld electrofishing equipment more reliably sampled small bass (Ozen and Noble 2005). However, practical application of these more selective techniques in typical Florida lakes affects the acc uracy and precision of assessing bass populations leaving boat electrofishing and rotenone as remaining choices ( Davies and Shelton 1996 ; Johnson and Nielsen 1996). For example, (1) seines do not function well in vegetated littoral zones; (2) fyke nets or hoop nets do not reliably catch bass in Florida lakes; (3) gill nets are not used for bass due to size selectivity (Hayes 1996; Hubert 1996). Replication is an issue with rotenone sampling because of high variability, indiscriminate mortality, and becaus e it is difficult to collect a large number of samples.
120 Early assessment of stocked juvenile hatchery bass may additionally be biased due to increased dispersal (movement) and more time spent in deeper offshore habitats ( Porak et al. 2011 ; FWC 2013 ). Acc ounting for these factors can increase confidence in the data and provide an efficacious sampling method less intrusive to the population. Hand held electrofishing, and rotenone sampling methods showed greater ability to collect bass <150mm, but are impra ctical to use in most lake sampling due to water depth and high mortality of stocked and non target wild fish, respectively ( Tate et al. 2003 ; Jackson and Noble 1995 ). Decreasing boat electrofishing transect lengths and increasing the number of transects provided greater precision and was more cost al. (2003) also suggested sampling greater numbers of electrofishing transects f or adult bass rather than fewer rotenone samp les to detect changes in abundance of both juvenile and adult bass was more efficient, and they also produced simulations that indicated electrofishing was more practical for assessing juvenile abundance compared to rotenone. The objective for our elect rofishing and census harvest comparisons evaluated sampling of stocked hatchery bass to predict when stock assessments with boat electrofishing effectively sampled sub adult bass populations. Combining the ability to stock 100 mm bass fingerlings by March with recruitment results from warmer climates (Ozen and Noble 2005) may shorten the time to detect contribution and year class strength. We compared electrofishing sampling t o complete census by draining six ponds that had been previously sto cked with j uvenile hatchery bass We evaluated size selectivity and percent population sampled with boat electrofishing gear at 2, 6, and 12
121 months post stock. We also observed any sampling induced mortality of both collection techniques. The mortality, if conside rable, was intended to possibly explain survival differences essential to pon d survival analysis in Chapter 2 of this body of work. A second objective was to possibly consider the use of catch per effort (CPE) to predict age 0 population density from ele ctrofishing CPE (Coble 1992) by regressing the known population size against the electrofishing CPE (Edwards et al. 1997). Methods Data collection utilized six rectangular 0.24 to 0.28 ha test ponds located at the Florida Bass Conservation Center (FBCC) in central Florida each containing a concrete kettle or U shaped raceway at the deepest end where the pond is drained. The maximum pond depth ranged from 1.5 to 1.6 m with a mean depth of 1 m in the center of each of the earthen ponds. The ponds were fi lled with gravity fed aged well water. Each pond was stocked with 200 juvenile bass each from three differing cohorts (88 117 mm TL of mean sizes of the three groups) in March of 2013 totaling 600 bass per pond. Bass stocked originated from 29 spawns collected October 18 th 20 th assured same aged bass. The three cohorts were not of consequence to this study and numbers were pooled as one population in each pond for analysis. A single 5 minute sample included electrofishing the entire shoreline peri pattern across the middle of each pond. Electrofishing sampling coincided with complete pond harvest in May, September, and the following March (2, 6, and 12 months post stocking, respectively) with electrofishing samples c ollected one to three days before census. All electrofishing sampling was completed in a single day per harvest event and sampled between 9 a.m. and 2 p.m. each time. Length and number of all bass caught
122 were recorded. Water quality parameters including temperature ( o C) and conductivity ( S/cm) were collected in each pond at each of the three sampling events (sensION5 Conductivity meter, Hach Co, Loveland, CO). The 4.9 m electrofisher boat consisted of two boom mounted circular anodes each fitted with eight 0.8 m braided stainless steel, cable droppers. An 11 hp generator delivered pulsed 120 hz DC and pulsed 60 hz AC at 4 amp current as suggested in moderate to high conductivity waters (Hill and Willis 1994). Bass were collected by a single dip netter and were held in a 190 L aerated li ve well filled with 0.5% salt solution. Electrofishing induced mortality was recorded 24 hr post shock. Ponds were drained in pairs to census all fish in the pond during the next three days post electrofishing. At each sampling period, all ponds were d rained to the in pond concrete kettle (2,275 L). All pond bottoms were manually surveyed to collect stranded fish during the drawdown of the pond and estimate pond bottom vegetation coverage. Each kettle was divided into three sections using 7 mm mesh al uminum screens. All fish were seined into one section of the kettle for analysis and each bass hand counted determining the actual population. Lengths (mm TL) and weights (g) were measured from 150 bass in each pond for comparison to the bass caught by e lectrofishing. This study was conducted in parallel with a study comparing survival of three cohorts of stocked hatchery bass. The results have no impact on the current study, but help expl ain sampling protocol (Chapter 2 ). Pure oxygen was supplied to t he kettle and fish were sedated with MS 222 during handling. A 10 x10 ft canopy provided shade over the kettle to prevent excessive water temperature increases.
123 Ponds were immediately refilled after sampling and large scale mortality incidents recorded if observed 24 hr after refilling. Analysis of selectivity was evaluated using Unistat version 6.0, UNISTAT Ltd. and Microsoft Excel 2010, Microsoft Corporation statistical software programs to generate all analysis, figures, and tables. A significan ce level of 0.05 was us ed in all statistical tests. The Shapiro Wilks test confirmed non normality, probability < 0.2, in several of the electrofishing samples prior to comparison. Kruskal Wallis (K W) one way ANOVA tests paired with Tukey HSD determined signi ficant differences between population s collected by electrofishing and pond census (McDonald 2009). Length frequencies (5 mm TL) were calculated to compare the lengths of bass captured in electrofishing samples to bass sampled during pond harvest at two (n = 900), six (n = 90 0) and 12 months (N = 394) post stock. Twelve month comparisons utilized all remaining bass, not a subsample. Electrofishing CPE of each bass population was regressed (linear least squares regression) against the actual existing de nsity at each sampling event to illicit selectivity of the sampling gear to predict when to assess age 0 bass post stock. Results Conductivity and water temperature measurements in each of the six pond replicates at 2, 6, and 12 months post stock showed little variation in conductivity between ponds and across all three sampling events, but temperatures fluctuated greatly between sampling events (Table 5 1.) Percent vegetation bottom coverage was grossly estimated by visual assessments as random 1 m 2 sa mple estimates ranged from 0 to 100% bottom coverage and priorities concerning the health of the fish impaired consistency in collecting manual estimates (Table 5 1). Southern Naiad Najas
124 guadalupensis and Muskgrass Chara sp comprised the majority of the submerged vegetation and algae with minimal emergent species including Pickerelweed Pontederia cordata and Knotgrass Paspalum disticum found around the edges and shallow end of the ponds. Electrofishing ineffectively sampled 5.2%, 1.9 7.8% range, of t he respective pooled bass populations in each pond two months post stock (Table 5 2). The pooled data showed that the mean ranks of electrofished (captured) bass mean lengths were significantly larger (K W; H = 8.3, 1 d.f., P = 0.0039) than the pooled bas s population mean sample (n = 900) 150.0 and 131.0 mm, respectively (Figure 5 1 ). Combined mortality caused directly by electrofishing from all six ponds equaled two bass or < 0.1% of all bass censused wh en the ponds were drained. Six months post stock, 9 17% (mean 13%) of the bass in the six research ponds were capt ured in electrofishing samples (Table 5 2). At six months post stock capture mean and population mean were not significantly different (K W; H = 3.1, 1 d.f., P = 0.0782), 154.7 and 161.2 mm, respectively (Figure 5 1). Observed 24 hr electrofishing mortality totaled six bass (0.37% of all remaining bass). In March, 12 months post stock, final electrofishing samples captured 31.4% (range 19.4 71.4%) of the respective pooled bass populations in all six research ponds (Table 5 2). No significant d ifference (K W; H = 2.07, 1 d.f. P = 0.1495) between mean lengths of electrofishing captured bass and the censused populations existed, 199.8 and 190.3 mm respectively (Figure 5 1). No electrofish ing mortality was observed during sampling. All remaining bass were transported to a 0.6 ha pond for future a ngling research. Twenty four hour electrofishing mortality and mortality from the cumulative effects of additional handing,
125 hauling, and stocking w ere not distinguishable, but four dead bass (1.0% of all remaining bass) were observed after the fish were moved into another research pond. Census of all remaining bass in each of the six replicate ponds allowed for the comparison of CPE (fish/min) to th e actual number of bass in each pond (Table 5 2). Catch per effort averaged 5.1 bass/min from ponds averaging 2,017 bass/ha two months post stock. Regression analysis showed no linear relationship (R 2 = 0.0064; P = 0.88) between CPE (Y) (bass/min) as a f unction of known density (X) two months post stock (Figure 5 2 ). Inverting the relationship to utilize CPE (X) as a predictor of bass density (Y) would be a useful tool for fisheries as CPE is more practical to collect and actual natural population densit ies are typically estimates. Placing CPE on the X axis to use as a predictor of bass density allowed us to examine this relationship across six kno wn bass densities and sizes. Catch per effort failed to eff ectively predict age 0 density (R 2 = 0.0064; P = 0.88) two months post stock in 131.0 mm mean (range 110 185 TL) sampled bass populations (Figures 5 1 and 5 3 ). Mean CPE increased to 7.0 bass/min at six months post stock, while at the same time the mean bass density decreased to 1,101 bass/ha. Even though the K W test (P = 0.0782) found no significant difference in size between the electrofished and population samples, regression analyses showed no significant relationship (R 2 = 0.363; P = 0.205) between CPE and bass density (Figure 5 2 ). The mathe matical model could not accurately or precisely predict bass density from CPE at 6 months in 161.2 mm mean (range 125 245 mm TL) sampled bass populations (Figures 5 1 and 5 3 ). Analysis 12 months post stock showed mean CPE decreased to 3.2 bass/min, but was strongly correlated (R 2 = 0.86; P = 0.0075) with bass density (mean = 270 bass/ha) in 190.3 mm mean (range,
126 130 320 mm TL) actual bass populations (Figure 5 1 and 5 2 ). The inverse prediction plot of density as a function of CPE showed CPE of a si ngle entire pond sample adequately predicted the density Y = 88.429x 12.638 (R 2 = 0.86; P = 0.0075) of age 1 bass (Figure 5 3 ). Discussion Timing post stock assessment to accurately reflect hatchery fish contribution is not only limited by individual f ish size susceptibility, but equally affected by the unknown size distribution of the stocked population at a selected time point. Our electrofishing samples two months post stock were biased toward larger individuals compared to the census population sam ple and failed to capture bass that reflected actual population size range. We observed schools of bass escaping the electrical field during sampling. Tate et al. (2003) suggested sampling precision increased with the number of samples of juvenile bass c ollected. We agree with their recommendation, but our data indicated that the abundance of either wild juvenile or stocked hatchery bass could still be greatly under estimated if not fully recruited to the sampling gear. According to the data in Figure 5 1, if mark recapture estimates were conducted, the results would under estimate the juvenile population as the majority of the population remained below 140 mm and ineffectively sampled. This could result in erroneous survival and percent contribution es timates and possibly inappropriate management decisions. This confirms the compounded error effects of assuming electrofishing samples adequately represent actual populations when > 60% of the actual censused populations in our six ponds (mean; 2,017 bass/ ha) were ineffectively sampled. Electrofishing samples more accurately represented actual size structure six months post stock with no significant difference reported between electrofished and
127 censused mean population lengths. The linear model built sho wing CPE as a function of density produced inaccurate, deflated estimates of catchability suggesting bass densities below 275/ha would have 0 bass per minute CPU from a single sample. Even though analysis showed electrofishing samples effectively represen ted actual size ranges six months post stock, regression analysis showed little correlation between CPE and actual density with only 13 % of the variability explained by age 0 density differences. Single samples of age 0 bass populations, 125 245 mm TL p rovided no relationship between bass fingerling CPE and density, indicating electrofishing estimates six months post stock still could misrepresent hatchery bass contribution data. Serns (1982) reported a strong correlation between fingerling CPE and den sity (mark recapture estimated) in similar sized age 0 Walleye (83.3 200.7 mm TL) to bass in our study. The reason for the discrepancy between our two studies is unclear. One plausible explanation is catchability may be inversely related with increasin g density or when CPE data is li mited by dipnetting efficiency ( McInerny and Cross 2000 ; Hansen et al. 2004). Mean bass densities in our six month samples were 42 times greater than densities reported by Serns (1982) and 23 times greater than the maximum densities reported by McInerny and Cross (2000). At times during our 6 month collection the single dipnetter was unable t o collect every stunned bass. Reduced catchability was imp oundments and the highest reported densities, 887 and 1,481 bass/ha, were similar to our 1,101 bass/ha mean (Hill and Willis 1994). Population density was shown to be inversely related to catchability decreasing CPE values and reducing efficacy of using CPE in density estimates (Simpson 1978 ; Hill and Willis 1994 ; McInerny and Cross
128 2000 ; Hansen et al. 2004 ). We selected for bass in our electrofishing samples ignoring all Lepomid spp. Size selective induced variation caused by dipnetting insignificantly detected differences between intensive (collect all fish spp.) and selective (just bass) collections (Twedt et al.1992). Other possible factors effecting catchability include species types, temperature, and habitat variation need further evaluation before CPE is to be utilized in estimating bass density six months post stock. Population size structure was effectively sampl ed in our ponds six months post stock, but we question strength of the CPE and density relationship at this time. Contrary to our st udy, electrofishing CPE appeared reliable in estimating LMB populations ab two North Carolina reservoirs (McInerny and Degan 1993) or when the entire shoreline of 12 Ohio impoundments was electrofished at least twice (Hall 1986). We sampled 100% of each pond s horeline only once in our study and suspected size selectivity, 125 245 mm, and lack of repetition per pond likely attributed to thi s difference between studies. Increasing the number of electrofishing samples in each pond may increase precision allowin g effective hatchery bass data collection at six month post stock of advanced size bass but predicting density or actual hatchery survival from CPE six months post stock needs further testing. Year class contribution estimates from stocked fish could be obtained at six months post stock of advanced fingerlings assuming the wild and hatchery fish populations are equally susceptible to the sampling gear. Wild bass populations may still consist of considerable numbers of uncatchable sized fish inflating hat chery contributions.
129 Sampling at 12 months post stock effectively captured a representative sample of the actual population. Electrofishing samples consistently captured 19 28% of the actual population in 5 of 6 replicate ponds. The outlier of 71.4% capture of bass in the sixth pond (Pond 18) was complicated by low population numbers as this represented 5 of the 7 bass remaining in the pond. We suspect the elevated capture rate resulted from reduced spatial competition from the remaining low density bass population allowing congregation near shoreline structure. As discussed in Reynolds (1996) and shown by Jackson and Noble (1995), improved catchability of larger sized fish was measured at the final 12 month pond harvest provided the mean size and size frequency of the actual population (Figure 5 2). Regression analysis positively correlated CPE to population density with 74 % of the variability in CPE explained by differences i n age 0 densities. This model could possibly predict densities in our hatchery pond bass populations with fingerling CPE from a single electrofishing sample. Similar models predicted juvenile Walleye densities in natural lakes using mark recapture popula tion estimates and a single yearling electrofishing CPE sample with 96% of the variability explained by differences in yearling CPE per surface acre (Serns 1982). Electrofishing CPE for age 0 bass at two and six months in our study poorly modeled age 0 ba ss densities. Hansen et al. (2004) reported similar findings on age 0 Walleye in 19 Wisconsin lakes and suggested the relationship between CPE and density was nonlinear. This indicated electrofishe d catchability of age 0 Walleye declined as population de nsities increased. Hansen et al. (2004) compared their model to the Serns (1982) model that was forced through the origin and suggested their model
130 more accurately estimated age 0 Walleye population densities over the linear regression analysis, but that the linear model crudely predicted population density. The creation of our models was not an attempt create a working model for use outside this study. The objectives were limited to determining the earliest effective time frame in which electrofishing e ffectively captured a sample of age 0 bass (<250 mm TL) that was representative of the size and abundance of juvenile bass in a population. This information could then be incorporated into developing evaluation protocols for future stocking projects. Similar to the relationship between electrofishing CPE and actual bass densities > 199 mm examined by Coble (1992) in a Wisconsin Lake and Edwards et al. (1997) in 14 hatchery ponds in Texas, we looked at linear regression analysis to view the approximate size electrofishing CPE effectively predicts density to potentially determine a reliable sampling time frame for age 0 to age 1+ recruitment to sampling gear. Edwards et al. (1997) showed that mark recapture model estimates from Coble (1992) underestimat ed actual bass density and suggested using electrofishing CPE to predict LMB densities and to identify the number of captured bass needed for improved mark recapture estimates. We utilized actual bass densities as a function of CPE in three sampling event s over one year in six hatchery ponds to predict when fisheries the time of stocking is important to account for in this process. Our data shows that at 12 months post st ock, CPE was a good indicator of actual age 1 bass density. These bass were five months post hatch at initial stocking or approximately 1.4 years old, and averaged 190 mm when sampled (Figure 5 1). Similarly, single CPE electrofishing
131 samples compared w ith mark recapture estimates proved a good indicator of age 1 wild Walleye populations (Serns 1983). Age and size at stocking needs consideration in determining assessment dates as CPE of smaller stocked fingerling bass may not reflect popu lation densitie s. Sampling bass initially stocked at 30 60 mm, 12 months post hatch would likely be comparable our six month data (Figure 5 1) as those bass were 11 months old at sampling and may lead to inflated estimates of age 1 abundance and possibly errant concl usions about the success of a stocking event. The sampling error should equally affect wild and hatchery bass. The potential inflated hatchery bass contribution would be the result of a greater percentage of the hatchery bass susceptible to boat electrof ishing. Our comparison of lengths and CPE to known population d ensities of age 0 and age 1 bass from six replicate hatchery ponds suggest stocking assessment prior to the majority (not the average) of the age 0 population exceeded a minimum of 140 mm coul d underestimate hatchery bass contribution and survival estimates. Assessments prior to the majority of wild population lengths surpassing 140 mm could over estimate contribution of advanced sized hatchery fish, and CPE data could possibly overestimate ag e 1 bass densit y. Unfortunately, actual size range in natural systems is difficult to determine and knowing when the majority of both stocked and natural bass age 0 year class populations become selective to electrofishing gear is prudent for effective da ta collection. Judgment based on our pond results indicated the majority of bass recrui ted to the gear six months post stock with no significant difference between the censused and electrofished sampled populations ( P blished,
132 but more realistic age 1 survival and recruit contribution needs to be estimate 12 months post stock or later Implications for Management Environmental conditions, including vegetation coverage (Tate et al. 2003; Hansen et al. 2004), conductivi ty levels ( Hill and Willis 1994 ; Reynolds 1996 ), turbidity, pH (Hansen et al. 2004), and water depth, as well as seasonal cha nges ( Carline et al. 1984; Schoenebeck and Han sen 2005 ) influence electrofishing CPE in a water body. Electrofishing CPUE was sho wn to be unreliable for accurately assessing changes in adult bass abundance as catchability varied by season and lake and should account for temporal movement patterns, but combining multiple year sampling data may increase the ability to detect change in a system ( Hangsleben et al. 2013 ). The broad variability and needs of individual systems was beyond the scope of this work which focuses on establishing a basic timeframe for post stocking assessment of juvenile hatchery reared Florida bass but needs co nsideration when designing sampling methods and selecting gear type (Sammons and Bettoli 1999; Ozen and Noble 2005). Concernin g Largemouth Bass in Florida, I recommend enhancement projects assess stocking results a minimum of one year post stock of advanc ed sized, > 80 mm, bass after the majority of the hatchery bass reach 140 mm TL to assure two things. First, to make sure the majority of the bass recruit to the gear type and avoid misleading results seen at two m onths post stocked data 150 mm recorded mean represented approximately 10% of the actual population. Second, analysis at this size and time will likely account for over winter mortality, a crucial aspect concerning age 0 bass recruitment (Ludsin
133 and DeVries 1997) yet the year cl ass should still be readily differentiated from the prior year or age 2 year class, although not absolute
134 Table 5 1. Individual pond characterisitcs including an estimated pond bottom coverage by submerged multicellual algae and macrophytes in six relica te hatchery ponds located in Webster, Florida stocked in March and sampled in May, September, and the following March. Surface area Pond Temperature Conductivity Secchi Depth Estimated Bottom Coverage Pond (ha) ( 0 C) ( S/cm ) (m) (%) 2 Month Sample, May 2013 Pond 9 0.28 27.8 574 1.6 25 Pond 10 0.28 27.8 589 1.6 25 Pond 17 0.24 27.4 526 1.5 33 Pond 18 0.26 27.5 544 1.5 33 Pond 34 0.27 27.9 499 1.6 15 Pond 35 0.26 27.4 562 1.6 15 6 Month Sample, Sept. 2013 Pond 9 0.28 31.1 588 1.6 70 Pond 10 0.28 31.6 602 1.6 70 Pond 17 0.24 30.7 521 1.5 75 Pond 18 0.26 30.1 569 1.5 75 Pond 34 0.27 31.0 555 1.6 60 Pond 35 0.26 31.8 511 1.6 60 12 Month Sa mple, Mar. 2014 Pond 9 0.28 20.5 489 1.6 75 Pond 10 0.28 20.1 522 1.6 75 Pond 17 0.24 20.0 547 1.5 60 Pond 18 0.26 20.9 499 1.5 75 Pond 34 0.27 20.9 538 1.6 70 Pond 35 0.26 21.0 561 1.6 70 Homogenous conductivites between sampling eve nts possibly resulted from nearly constant addition of 700+ S/cm well water.
135 Table 5 2. Number of bass collected per pond per single five minute electrofishing sample event, t otal number of bass harvested per pond following draining, percent (%) of th e actual population electrofished, catch per effort (CPE, bass/min) electrofishing, and known density (bass/ha) collected at 2, 6, and 12 months post stocking six ponds at the Florida Bass Conservation Center Each pond was initialy stocked with N = 600, 8 8 to 117 mm bass at a rate of 2,470 bass/ha. Pond 9 Pond 10 Pond 17 Pond 18 Pond 34 Pond 35 Mean (SD) 2 Month Sample, May 2013 Total shocked 18 15 10 35 40 35 25.5 (12) Total harvested 452 478 528 448 532 506 491 (37) % Electrofished 4. 0% 3.1% 1.9% 7.8% 7.5% 6.9% 5.2% (2.5) CPE, bass/min 3.6 3 2 7 8 7 5.1 (2.5) Density, bass /ha 1,858 1,965 2,170 1,841 2,187 2,080 2,017 (152) 6 Month Sample, September 2013 Total shocked 26 35 39 29 53 28 35 (10) Total harveste d 245 238 272 306 314 232 268 (35) % Electrofished 10.6% 14.7% 14.3% 9.5% 16.9% 12.1% 13.0% (2.8) CPE, bass/min 5.2 7 7.8 5.8 10.6 5.6 7 (2) Density, bass/ha 1,007 978 1,118 1,258 1,291 954 1,101 (146) 12 Month Sample, March 2014 Total shocked 24 15 23 5 19 10 16 (7) Total harvested 86 59 94 7 98 50 66 (35) % Electrofished 27.9% 25.4% 24.5% 71.4%* 19.4% 20.0% 23.4% (3.6) CPE, bass/min 4.8 3 4.6 1 3.8 2 3.2 (1.5) Density, bass/ha 353 242 386 29 403 206 270 (142) Pond 18 was removed from the mean percent electrofished at the 12 month sample, 31.4% (19.9).
136 Figure 5 1 Evaluates ability of boat electrofishing to effectively sample known stocked Florida bass age 0 to age 1 populati ons (>105 and < 320 mm) a t 2 A), 6 B), and 12 C) months post stock from six pooled 0.24 0.28 ha ponds in Webster, Florida. Relative (%) frequency shows the ability to effectively represent actual size distribution between collection techniques. Mean percent population capture increased as the population increased in length. The 12 month sample lists an adjusted mean percent ( ) population captured to reflected removal of one of the six replicates. The y and x axis frequencies and lengths were adjusted accordingly at each sa mpling period to maintain visual representation of the 5 cm length groups. Comparisons between listed distributions are not intended or applicable. 0% 2% 4% 6% 8% 10% 12% 14% 16% 18% 20% 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 Relative Frequency Length Group (5 cm) Mean population % captured, 5.2%. 2 m post stock Captured Bass, mean = 150 mm; n = 153 Bass population, mean = 131 mm; n = 900 0% 2% 4% 6% 8% 10% 12% 14% 16% Relative Frequency Length Group (5 cm) Mean population % Captured, 13.01%. 6 m post stock Capture bass mean,154.7mm; n = 210 Bass population, mean = 161.2mm; n = 900 B A
137 Figure 5 1 Continued 0% 2% 4% 6% 8% 10% 12% Relative Frequency Length Group (5 cm) Mean population % captured, 31.4% (23.4%). 12 m post stock Capture Bass, mean = 199.8 mm; n = 96 Bass population, mean = 190.3mm; N = 394 C
138 Figure 5 2 Least squares regression analysis of electrofishing cat ch per effort (bass/min) as a function of known bass densities (bass/ha) from six replicate ponds at 2, 6 and 12 months post stock. The line reflects the ability to collect a representative population sample of Florida bass originally stocked at 88 117 mm at selected time frames The y and x axes were adjusted to reflect changing bass population numbers per sampling event over the 12 month study period. y = 0.0013x + 2.411 R = 0.0064 P = 0.88 0 1 2 3 4 5 6 7 8 9 1800 1850 1900 1950 2000 2050 2100 2150 2200 2250 CPE (bass/min) Density (bass/ha), 2 m y = 0.0083x 2.1537 R = 0.363 P= 0.205 0 2 4 6 8 10 12 0 500 1000 1500 CPE (bass/min) Density (bass/ha), 6 m y = 0.0098x + 0.558 R = 0.86 P = 0.0075 0 1 2 3 4 5 6 0 100 200 300 400 500 CPE (bass/min) Density (bass/ha), 12 m
139 Figure 5 3 Least squares regression analysis of known bass densities as a function of electrof ishing catch per effort. The line reflects the moderate ability to predict bass density from catch per effort in an attempt to determine when post stoc k assessment of hatchery bass was efficient and effective. The y and x axes were adjusted for catch pe r effort per sampling event over the 12 month study period. y = 4.8213x + 1992.1 R = 0.0064 P = 0.88 1800 1850 1900 1950 2000 2050 2100 2150 2200 2250 0 2 4 6 8 10 Density (bass/ha) CPE (bass/min), 2 m y = 43.686x + 795.37 R = 0.363 P = 0.205 0 200 400 600 800 1000 1200 1400 0 2 4 6 8 10 12 Density (Bass/ha) CPE (bass/min), 6 m y = 88.429x 12.638 R = 0.86 P = 0.0075 0 50 100 150 200 250 300 350 400 450 0 1 2 3 4 5 6 Density (bass/ha) CPE (bass/min), 12 m
140 CHAPTER 6 CONCLUSIONS Utilization of Hatchery Reared Bass Results from these studies validate utilization of either live or pellet reared hatchery bass as options for sto ck enhancement projects My results determined that live and pellet reared bass equally survive d in number to age 1 under the specific culture and stocked environment protocols described including : introduction of live prey in tanks low predator densities ample vegetation co verage. It is important to note both live and pellet reared bass are hatchery reared fish and still remain less optimal then actual wild bass. Hatchery reared product performance compared to wild fish performance is not devoid of value, but is less impo rtant in this body of work specifically considering comparisons of actual current culture product capabilities. Hatcheries can partially simulate but remain typically unable to completely replicate and produce a completely wild environment due to elevate d stocking densities and amounts requested, providing the need to assess differing production strategies Future stockings requiring small numbers of bass may want to duplicate my pond protocols creating natural habitats for foraging skill training and pr edator avoidance. Exposing hatchery fish to natural conditions as found in my research ponds created an environment where intensively reared, pellet fed or live prey reared hatchery bass could acclimate to wild conditions, transition to capturing and feed ing on live prey and escaping predation. After two months in these rearing ponds, 83% (2,050/ha or 830 bass/acre) of the pellet fed bass and 88% (2,173/ha or 880/acre) of the live feed reared bass were harvested and could have been used for stock enhance ment projects by releasing them in natural lakes or rivers across the state of Florida. My research
141 indicates that domestication effects can be short term; indicating that after two months in a conditioning pond the survival of hatchery fish might begin t o approach survival rates experienced by wild fish. Broodstock origin (wild caught or hatchery produced) h atchery s pawning techniques rearing densities and grow out protocols also need consideration when comparing hatchery products My results showed the utilized rearing technique specific to l ive and pellet reared bass did not favor one product s survivability over another one year post stock comparatively Wild broodstock and identical initial sp awning and nursery pond techniques were utilized in m y study, but r earing densities differed between advanced l ive and pellet reared treatments during grow out B oth were reared at significantly higher densities in the nursery and grow out phases than expected in wild populations at comparable body size (P arkos and Wahl 2010). F urther research is required to understand the potential long term effects of spawning techniques including bloodstock origin ( Hhn et al. 2014) and rearing densities from hatch (Lorenzen et al 2012). Based on my results, I recommen d s tocking bass in low predator density lakes as early in the season as possible on adequate sized forage, may allow for greater size and survival potential prior to first winter. Stocking early with the objective to achieve larger bass before winter, co mmonly suggested as a crucial aspect of wild bass survival ( Garvey et al. 1998 ; Post et al 1998 ) and supported by my results, can be completed by stocking northern latitudes from the hatchery site with fingerlings or stocking southern latitudes with advanc ed fingerlings reared over winter in rac eways. My survival results agreed with the reports suggesting increasing length attained by first winter may
142 increase recruitment to the age 1 populatio n ( Goodgame and Miranda 1993; Miranda and Hubbard 1994). Final ly, c omparing survival and performance of multiple hatchery reared Florida bass types one year post stock showed equal viability for stock enhancement. The continued departure from wild survival estimates is not singu larly a result from these specific gro w out protocols and likely a combined interaction of multiple hatchery induced effect s H atchery Reared Bass Angling Vulnerability The comparison of catchability be tween live and pellet reared hatchery bass showed different production protocols insignif icantly impacted hook and line vulnerability specifically between hatchery reared types Implications of this research relate back to long term hatchery domestication concerns and specifically show no catchability differences related to the differing prod uction protocols. There still ma y be differences between truly wild bass and hatchery bass catchability, which future research could identify, but hatcheries unfortunately are unable to produce wild bass limiting the need for the comparison. My results c onfirm either hatchery product may be a valuable tool for fisheries manag e ment speci fically concerning angling vulnerability and maintaining or improving catch rates A quaculture Based Fisheries Management Utilization of cultured fish for effective fisher ies management requires understanding life history processes and site specific water body characteristics. My results demonstrated performance scenarios from stocking four sizes of bass at increasing densities. The intention focused on simulating actual natural bass densities in controlled ponds to observe survival and performance outcomes. Results predicted possible outcomes concerning stocking size, density, and timing for hatchery bass. The
143 compiled data elicited scenarios concerning possible stocki ng strategies for fingerling and advanced fingerling bass. Survival and growth tendencies favored lower densities for fingerling ba ss, but were more forage depende nt for advanced fingerlings. This suggested timing may be more important than stocking siz e providing potential for stocking more cost effective fingerling Finally, my results may be useful for modeling potential results of stocking on pre existing age 0 populations. Utilizing my results as the pre existing wild population against additiona l es timated stocking rates the resulting predictions could predict stocking efficacy and im prove hatchery resource efficiency. These results demonstrated generalized trends for enhanced stocking decisions and not specifically depicting actual stocking ex pectations. Repeating this study with the addition of live prey (fish) would be beneficial Post Stock Assessment Timing assessment s to accurately reflect actual age 0 to age 1 populations as well as hatchery fish contribution s are not only limited by in dividual fish size susceptibility, but equally affected by the unknown size distribution of the population s at a selected time point. My research, based on populations of known size and distribution showed the importance of sampling after the majority of the population recruited to the sampling gear (> 140 mm). Unfortunately, the size structure of the stocked bass as well as the natural age o population will be un known in natural ponds and possibly result in errant estimates as my early results showed el ectrofishing samples were biased toward large r bass. Regression analysis adequately correlated CPE to known population densities and allowed the creation of a model that predicted po pulation density from CPE one year post stock Lastly, my data provided evidence that future stock assessment evaluat ions be completed after a minimum of six months
144 post stock of advanced fingerling. The most reliable size structure data and estimates of abundance were obtained at one year post stock. The 12 month recommenda tion may need extension in more northern, cooler climates. Future Research Best Hatchery Product Lorenzen (2006) modeled mortality in wild and released hatchery fish and showed higher mortality for released hatchery fish compared to wild fish of the same length. Even though hatchery fish reared in tanks, ponds, or cages experience higher survival (from the rearing environment) compared to fish of similar size in natural systems (Lorenzen 1996), cultured fish tend to be less fit then their wild conspecifi cs after release into natura l systems Different combinations of culture protocols are required to produce outcomes specific for the proposed final purpose of the cultured fish (Lorenzen et al. 2012). The three treatments employed identical wild caught br oodfish and spawning protocols designed preserve natural selectio n The negative implications of using manipulated broodstock in hatchery release programs relate to reduced fitness and poor contribution to future year classes (Fleming and Petersson 2001 ; Araki et al. 2007 ; Araki and Schmid 2010). My results suggested that differing grow out protocols did not significantly affect age 1 recruitment potential. It would be valuable to examine how differing spawning techniques and rearing densities fry and f ingerling, affect hatchery reared bass comparing results among common hatchery practices and to wild fish. Hhn et al. ( 2014) demonstrated stocking hatchery reared pike fry was still only additive in the absence of wild natural recruitment and that manipu lated spawned hatchery fry showed a competi tive disadvantage to pond spawned c onspecifics. This indicated a decline in fitness that re sulted from artificial hatchery induced (strip
145 spawning) reproduction opposed to their simulated natural production in ha tchery ponds. The elevated stocking densities utilized in culture environments may alter behavioral traits increasing aggressiveness. Mor e effort is required evaluating effects of increased survival resulting from predator free culture environments and ho w culture developed behavior traits, accounting for elevate d culture densities, relate to cultured fish survival stocked in more complex unpredictable natural environments (Lorenzen 1996; Huntingford 2004; Thorpe 2004). Adjusting densities at fry and finge rling production stages product at the expense of culture product efficiency. These results could implicate possible better hatchery practices and where the deviation of survival between wil d and hatchery fish occurs. Post Stocking Evaluation D epende nt on a more subjective scale, q ualifying success or determining if stocking wa s additive or replacement relies on multiple factors that need clarifying. Further comparative research is require d to quantify success. Success can be interpreted differently between stocking project s or evaluated on completely different criteria A lthough every stocking project is classified at some level between successful or failure continued hatchery stocking evaluations should focus more on respective natural year class contributions accounting for density and growth dependent mortality It is important to consider specific spawning and rearing processes incorporated in bass production Different production protocols including domesticated (not wild) broodstock (Petersson et al. 1996) and lack of foraging training ( Reiriz et al. 1998 ; Rachels et al. 2012) can potentially give different results. Conversely the high mortality rates of
146 naturally produced age 0 bass and the lack of strong correlation of bass stock size to limit yearly recruitment (Allen et al. 2011) may diminish the necessity to stock this particular species is so high. Any additional mortality initially caused by lingering post stock domestication could simply be absorbed but requires continued research for validation Genetic linked Growth Implications Finally, the significantly increased growth rate o f the Hatchery G rade out bass treatment needs further investigation. Understanding that fast juvenile growth influenced by culture conditions needs investigation as well. Isolating parent pairs that predictably scale in Florida. Continued research should focus on confirm ing if this is a genetic trait and determining sampling protocols identifying individuals carrying the identified trait (Domingos et al. 2013). Selective bree ding to manipulate phenotypes displayed by a population is purposely conducted in commercial aquaculture to increase the occurrence of heritable traits of high eco nomic importance (growth rate) ( Tave 1993 ; Gjedrem et al. 2012 ) Typically, these facilities produce fish for consumption, not for stock enhancement purposes, allowing for the accepted disregard of maintaini ng genetic diversity and increased induced inbred and crossbred lines (Falconer and Mackay 1996). Implications for stocking these bass would be limited to isolated water bodies to produce trophy fisheries and possible re introduction of the trait to large natural populations impacted by high harvest pressure.
147 APPENDIX GROW TH AND PERFORMANCE GENERAL LINEA R MIXED MODEL RESULTS
148 Table A 1 General linear mixed model ANOVA analysis depicting F Stat, P value, R 2 (P val ue) between three Florida bass cohorts (Hatchery Standard, Grade out, and Forage ) length and weight at stocking and three census harvest dates. P value and R 2 accounts for pond effect between the six replicate P F Stat P value R 2 "Pond effect" Sample date Length Weight Length Weight Length Weight Length Weight March, 2013 1586.5 903.7 <0.0001 <0.0001 1.00 0.99 0.78 0.22 May, 2013 189.0 97.1 <0.0001 <0.0001 0.97 0.95 0.20 0.37 September, 2013 87.2 92.2 <0.0001 <0.0001 0.96 0.96 0.0005* 0.0001* March, 2014 38.0 32.9 <0.0001 <0.0001 0.89 0.88 0.22 0.45 *Denotes when differences between the ponds accounted for a significant amount of the variation between the three cohorts.
149 Table A 2. General linear mixed model ANOVA analysis comparing F Stat, P value, R 2 (P value) between three Florida bas s cohorts (Hatchery Standard, Grade out, and Forage ) cumulative population growth rates in length and weight from initial stocking to three census harvest dates. P value and R 2 significant at P F Stat P value R 2 "Pond effect" Duration Length Weight Length Weight Length Weight Length Weight March May, 2013 4.6 3.4 0.038* 0.073 0.64 0.61 0.23 0.21 March September, 2013 11.1 28.1 0.003* 0.0001* 0.90 0.94 0.0004** 0.0001** March March, 2014 12.8 25.4 0.002* 0.0001* 0.78 0.89 0.20 0.42 **Denotes when differences between the ponds accounted for a significant amount of the variation between the three cohorts
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170 BIOGRAPHICAL SKETCH Michael Matthews was born to Davi d and Cindy Matthews December, 1975 in Cincinnati, OH. He spent most of his childhood fishing with his father and grandfather and still regards the day he received his first Bass Pro Shops catalog as one of the Top 10 greatest days of his young life. In 1994, he began a four year B.S. program at the University of North Carolin a at Wilmington and majored in marine b iology and minored in c hemistry. Th e incredibly diverse group of Professors at UNCW encouraged Michael to follow his passion s for i chthyology anatomy, physiology, and aquaculture. In the summer of 1995 he spent 2 months working at a prawn culture facility in Iloilo, in the Philippines. A fter graduation in May 1998 Michael thought about a career studying s hark anatomy and behavior, but his new wife Dawn tho ught it best for him to attend g raduate school instead. He began graduate school at Auburn University in the Fall of 1998. Michael worked for Drs. Leonard Lovshin and Ronald Phelps f or two years while llied a quaculture in the summer of 2000. Michael and Dawn relocated to Florida in the fall of 2000 where Michael began his career with the Florida Fish and Wildlife Conservation Commission at the Tenoroc Fish Management Area. Three years later he was hired as the Intensive Production B iologist at the new Florida Bass Conservation Center in Webster, FL. In the summer of 2011 he began his Ph. D. work with Dr. Kai Lorenzen while continuing his fish production responsibilities for the State of Florida and defended in the spring of 2015. Michael is very grateful for the opportunity and continued academic expansion integrating the fields of aquacu lture an d fisheries management Dr. Lorenzen and additional U niversity of F lorida advisors provided. Michael plans to continue his academic endeavors after graduation, but will first take his two children Courtney and Nathan on a well earned
171 week long fish ing trip in the mountains. They have been extremely understanding of doctoral degree.