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Evaluation of Largemouth Bass Exploitation and Potential Harvest Restrictions at Rodman Reservoir, Florida


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EVALUATION OF LARGEMOUTH BASS EXPLOITATION AND POTENTIAL HARVEST RESTRICTIONS AT RODMAN RESERVOIR, FLORIDA By KRISTIN RENE HENRY A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2003

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Copyright 2002 by Kristin Rene Henry

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To my parents Robert and Jacquieline Henry, thank you for all your love and support.

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ACKNOWLEDGMENTS My gratitude and appreciation go out to Dr. Mike Allen for serving as my advisor, mentor, and committee chair; Dr. Daniel Canfield Jr., James Estes, Dr. Ramon Littell, and Dr. Debra Murie for serving as members of my committee; and Robert Hujik and Eric Nagid for dealing with the publicity associated with the study, processing all of the tag returns, and providing advice and assistance throughout the study. I thank the following people who made significant contributions to the field portion of the study: J.Berg, T. Bonvechio, R. Burns, P. Cooney, T. Curtis, K. Dockendorf, M. Duncan, S. Gardieff, J. Greenawalt, J. Hale, B. Hujik, G. Kaufman, S. Keller, E. Naged, S. Naged, W. Porak, M. Randall, J. Rowe, B. Sergent, W. Tate, K. Tugend, P. Wheeler, and G. Yeargin. Finally, I thank everyone who provided advice and comments throughout the study; their help has been greatly appreciated. Funding for this study was provided by the Florida Fish and Wildlife Conservation Commission. iv

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TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES............................................................................................................vii LIST OF FIGURES.........................................................................................................viii ABSTRACT.......................................................................................................................ix INTRODUCTION...............................................................................................................1 METHODS..........................................................................................................................5 Study Site........................................................................................................................5 Tagging Study.................................................................................................................5 Age-and-Growth.............................................................................................................8 Analysis...........................................................................................................................8 Tagging Study..........................................................................................................8 Age-and-Growth....................................................................................................13 Regulation Simulations.................................................................................................15 RESULTS..........................................................................................................................18 Tagging Study...............................................................................................................18 Age-and-Growth...........................................................................................................22 Regulation Simulations.................................................................................................23 DISCUSSION....................................................................................................................35 FURTHER STUDY...........................................................................................................43 APPENDIX A REWARD SIGN-1........................................................................................................46 B TAG-RETURN INVOICE............................................................................................47 C REWARD SIGN-2........................................................................................................48 LIST OF REFERENCES...................................................................................................49 v

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BIOGRAPHICAL SKETCH.............................................................................................53 vi

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LIST OF TABLES Table page 1. Estimated catch of 2,638 largemouth bass tagged and released at Rodman Reservoir, Florida....................................................................................................................30 2. Tag loss rates for single-tagged (p) and double-tagged (p 2 ) largemouth bass at Rodman Reservoir.................................................................................................32 3. Quarterly catch rates of tagged fish caught from Rodman Reservoir during the first 3 quarters of 2001 and 2002...........................................................................33 vii

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LIST OF FIGURES Figure page 1. Rodman Reservoir located in Putnam and Marion Counties, Florida..........................25 2. Von Bertalanffy growth models fit to mean-length-at-age values for male (triangles) and female (squares) largemouth bass collected from Rodman Reservoir in January 2002..........................................................................................................26 3. Weighted catch curve based on number-at-age data for all fish collected during electrofishing transects conducted at Rodman Reservoir in January 2002............27 4. Estimated annual harvest of all fish..............................................................................28 5. Estimated annual catch of all fish.................................................................................29 viii

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science EVALUATION OF LARGEMOUTH BASS EXPLOITATION AND POTENTIAL HARVEST RESTRICTIONS AT RODMAN RESERVOIR, FLORIDA By Kristin Rene Henry May 2003 Chair: Dr. Micheal S. Allen Major Department: Fisheries and Aquatic Sciences Rodman Reservoir is considered a premier largemouth bass fishery in Florida, but the large-fish ( 510-mm TL) potential of the reservoir could potentially be enhanced with a harvest restriction. I conducted a variable reward tagging study to estimate exploitation of largemouth bass at Rodman Reservoir. A total of 2,650 largemouth bass 345-mm TL were tagged from 2000-2002 using Hallprint dart-style tags. Monetary rewards for tag returns ranged from $5-$100. Total mortality of largemouth bass was estimated from a catch curve and gender-specific growth rates were determined from annuli on sagittal otoliths. An age-structured model was used to simulate the response of the fishery to various harvest restrictions. Tag returns showed that 42% of the largemouth bass at Rodman Reservoir were caught in 2001; 11% of the population was harvested, whereas 31% of the population was caught and released. Total annual mortality was estimated at 49% and natural mortality at 38%. Length-specific exploitation rates increased with fish size, indicating a preference among anglers for ix

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harvesting large fish. Simulations showed that harvest of memorable-sized fish was highest under a 510-mm minimum length limit. Overall total catch (fish 254-mm TL) and total catch of memorable-sized fish ( 510-mm TL) under the 510-mm minimum length limit were second only to a catch and release regulation. Therefore, a 510-mm minimum length limit would maximize angler catch rates but also allow anglers to harvest large ( 510-mm TL) fish. x

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INTRODUCTION Largemouth bass Micropterus salmoides support some of the most important freshwater fisheries in the United States. The U.S. Fish and Wildlife Service estimates that approximately 11.3 million American anglers pursue black bass (U.S. Department of the Interior 2002). Freshwater fishing expenditures in Florida totaled an estimated $720 million in 1996, with 663,000 anglers targeting black bass. This is more than twice the number of anglers that target any other freshwater sportfish in Florida (U.S. Department of the Interior 1998). Use of harvest restrictions has become an important part of maintaining and improving largemouth bass fisheries. Harvest restrictions typically include length limits, slot limits, and bag limits. Objectives of harvest restrictions are to manipulate predator-prey relationships, increase growth rates of abundant but stunted individuals, increase population size, increase the number of large fish, and/or increase angler catch rates (Noble and Jones 1993). Wilde (1997) compiled data from 49 minimum length-limit evaluations and 42 slot-limit evaluations for largemouth bass at 88 lakes across the United States. He identified trends in the response of largemouth bass populations to minimum length and slot limits. Wilde (1997) found that minimum length limits increased catch rates of largemouth bass, whereas slot limits (305-381 mm TL) increased the relative abundance of quality and preferred-size largemouth bass. No evidence indicated that minimum length limits increased the proportion of large fish or that slot limits increased angler catch rates 1

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2 (Wilde 1997). A length-limit evaluation at Lake Harris, Florida, found a 40% increase in angler catch rate two years after implementation (Benton and Douglas 1994). This increase concurred with the length limit trends described by Wilde (1997). Managers and research scientists have used computer models to predict the impact of regulations on a fishery (Orth 1979; Zagar and Orth 1986; Beamesderfer and North 1995; Allen et al. 2002). Zagar and Orth (1986) modeled the effects of minimum length and slot limits on a hypothetical largemouth bass fishery to identify optimal regulations. They recommended a 356-mm minimum length limit to managers interested in maximizing biomass harvested or a 305-406 mm slot limit for creating trophy bass fisheries (Zagar and Orth 1986). Models have been used to assess largemouth bass population responses to length limits on national and regional levels. Beamesderfer and North (1995) characterized largemouth bass populations within the Untied States by productivity level (i.e., low, average, or high growth and natural mortality rates) and simulated the effects of length limits at each productivity level. Beamsderfer and North (1995) found that population responses to length limits (e.g., changes in yield, harvest, and biomass) were strongly influenced by the productivity level of the population and that managers options increase with population productivity. Allen et al. (2002) assessed the potential benefits of harvest restrictions based on growth and total mortality of 32 largemouth bass populations in Florida waters. They indicated that length limits would improve yield and total catch if growth was at least average and natural mortality was not substantially higher than exploitation; they also found that high length limits reduced harvest regardless of growth rate but improved angler catch rates.

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3 Rodman Reservoir is a popular largemouth bass fishery with a reputation for producing trophy fish. According to the Florida Fish and Wildlife Conservation Commission (FFWCC) Big Catch program, a largemouth bass must be 3.6-kg or 610-mm TL to qualify for trophy status. During the spring of 2000 two largemouth bass were caught from the reservoir weighing 7.7-kg and 6.8-kg (Dan Canfield, Florida Lakewatch, personal communication). The state record is currently held at 7.8-kg (FFWCC); thus Rodman Reservoir has the ability to produce trophy bass. The largemouth bass population at Rodman Reservoir, Florida has historically been managed under statewide regulations. Regulations during standard operating conditions (5.49-m above mean sea level) restrict angler harvest with a five fish bag limit and 356-mm length limit, and allow only one fish in the bag limit to exceed 550-mm TL. Additional regulations have been applied to the reservoir during periods of drawdown. Regulations for the 2001/2002 drawdown (3.35-m above mean sea level) maintained the five fish bag limit while increasing the length limit to 610-mm TL. Length limit exemptions, however, have been granted to tournament anglers by the FFWCC at all operating levels of the reservoir. Anglers have expressed a desire for managers to further improve the largemouth bass fishery at Rodman Reservoir. In response, I evaluated the potential for harvest restrictions to enhance the largemouth bass fishery at Rodman Reservoir by identifying regulations that would increase angler catch rates and/or increase the occurrence of large fish ( 510-mm TL) in the creel. The objectives of this study were to (1) estimate angler exploitation of largemouth bass using a reward-based tagging study; (2) estimate total annual mortality using catch curve analysis; (3) estimate age and growth using otoliths;

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4 and (4) employ computer models, based on these estimates of exploitation, total annual mortality, and age and growth, to identify harvest restrictions that would increase overall total catch (fish 254-mm TL), total catch of large fish ( 510-mm TL), and harvest of large fish at Rodman Reservoir.

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METHODS Study Site Rodman Reservoir is a 3,700-ha eutrophic system located in Putnam and Marion Counties, Florida. A relict of the Cross Florida Barge Canal project, Rodman Reservoir encompasses a 26-km flooded section of the Ocklawaha River stretching from the Eureka dam to the Senator George Kirkpatrick dam. Three distinct areas characterize the reservoir. Upstream the reservoir consists of floodplain forest and riverine habitat. A transition zone consisting of flats, stumps, and a submerged river channel follows leading into the main pool of the reservoir (Canfield et al. 1993). The reservoir has a mean depth of 2.11-m (Canfield et al. 1993). Six boat launches provide access to the reservoir. Under normal operating conditions Rodman Reservoir is maintained at 5.49-m above mean sea level (msl). The reservoir is drawn down at three to five year intervals to control aquatic macrophytes. During drawdown periods the reservoir is reduced to 3.35-m above msl, decreasing the flooded area by approximately 2,000 hectares (R. Hujik, FFWCC, personal communication). The most recent drawdown event began December 1, 2001 and lasted until April 1, 2002. During this time a 610-mm minimum length limit was placed on the largemouth bass fishery. This temporary regulation was intended to prevent excessive harvest of largemouth bass during the drawdown. Tagging Study I divided the reservoir into four areas (Figure 1) and tagged an approximately equal number of fish in each area. Area one included water north of the barge canal, west of 5

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6 the state route 19 bridge, and east of the Kenwood entrance. Area two included all water south of the barge canal and east of the Kenwood entrance. Area three included water between the Kenwood entrance and the power lines at Orange Springs and Area four include all water between the power lines and the entrance to Paynes Landing (Figure 1). No fish were tagged upstream of Paynes Landing. Fish were collected for tagging with a boat electrofisher and from angler tournaments. Largemouth bass were captured using a 4.88-m jon boat outfitted for electrofishing with a Coffelt VVP-15 electrofisher, as well as a Smith-Root SR-18H electrofishing boat outfitted with a 9.0 GPP electrofisher. Both systems output DC current at five to seven amps. All largemouth bass 345-mm TL and greater were measured to the nearest millimeter total length (TL), tagged, and released into approximately the same area from which they were captured. Tournament-caught fish 345-mm TL were measured to the nearest millimeter, tagged, and released into the barge canal between Areas 1, 2, and 3 (Figure 1). I assumed, based on previous age-and-growth data for largemouth bass at Rodman Reservoir (Allen et al. 2002), that all tagged fish 345-355 mm TL would recruit to the fishery ( 356-mm TL) within four months of tagging. Largemouth bass were tagged with 103-mm long plastic Hallprint dart tags with a barb (18-mm long) and orange streamer (85-mm long). The monetary reward value, return address, and a tag specific identification number were printed on the streamer of each tag. Tags were injected into the body of the fish below the spiny dorsal fin rays using a hollow stainless steel needle. When injected the barb of the tag hooked behind a

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7 pterygiophore and the streamer extended in a posterior direction at a 45-degree angle to the body. Largemouth bass were tagged during two tagging periods to allow estimates of exploitation in 2001 and 2002. The length of each tagging period was dictated by the amount of time it took to tag approximately 1,300 fish. Tagging period one lasted from November 2000 to March 2001 and tagging period two lasted from December 2001 to January 2002. Fish were tagged with either one tag (single-tagged) or two tags (double-tagged) during both tagging periods. Double-tagged fish were later used to estimate tag loss rates. Single-tagged fish had a monetary reward value of either $5 or $50 and double-tagged fish had a monetary reward value of $10 (2-$5 reward tags), $55 (1-$5 and 1-$50 reward tag), or $100 (2-$50 reward tags). Double-tagged fish worth $100 were only released during tagging period-2. The variable-rewards offered for tag returns were later used to estimate the reporting rate of tags. No tournament fish were double tagged, due to a desire to minimize the handling time of these fish. Tag returns from double-tagged fish were considered as a single return. Press releases to local newspapers and reward signs were used to inform the public about the study. Reward signs (Appendix 1) were posted at fishing access points around the reservoir and at local bait and tackle shops. Mailer envelopes with tag-return forms were available at local bait and tackle shops and were provided to anglers upon request. Tag-return forms requested the angler name, address, social security number (required to receive reward), date and location fish was caught, approximate length, fate of the fish (i.e., harvested or released), and if the fish was caught during a tournament (Appendix 2).

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8 Age-and-Growth Age and growth of largemouth bass at Rodman Reservoir were estimated using fish collected with electrofishing in January 2002. All largemouth bass collected during 20-minute electrofishing transects were measured to the nearest millimeter total length. Five fish per centimeter group up to 39-cm TL and all fish 40-cm TL, excluding fish > 5.9-kg, were collected and returned to the laboratory where weight and gender were determined, and otoliths were removed. Sagittal otoliths were removed from sub-sampled fish and read in whole-view under a dissecting microscope by three independent readers. Otoliths that were 3-years or older and otoliths with reader discrepancies when examined in whole-view were sectioned (Hoyer et al. 1985). Two to four 0.50-mm sections were cut from the focus of each otolith using a South Bay Technology low speed diamond wheel saw (model 650). Sections from each fish were mounted on a half-frosted slide using Thermo Shandon synthetic mount. Sectioned otoliths were read under a compound microscope by a minimum of two independent readers. Sectioned otoliths with reader discrepancies were re-read by the original readers as well as one additional reader. If the discrepancy remained, the otolith was discarded. Crawford et al. (1989) found the formation of annuli to occur as early as April for largemouth bass in Florida lakes, therefore because fish were collected for age-and-growth in January I assumed a January birth date and assigned each fish an age one year greater than the number of rings observed on the otolith. Analysis Tagging Study Tag returns were adjusted for tag loss, tagging-related mortality, and non-reporting, prior to estimating total annual catch and angler exploitation. Tag returns and

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9 electrofishing recaptures of double-tagged fish were used to estimate tag loss. Anglers that returned single tags from double-tagged fish were contacted by phone to verify that only one tag was present at the time of capture. The time between tagging and recapture was recorded for all double-tagged fish. I assumed that tag retention was linearly related to time-at-large and developed two models, as per Miranda et al. (1997), to estimate the logistic probability of tag loss (logit(l)) based on the period (P) in which the fish were tagged: logit() = timelab1( ) (1) where a is the intercept estimate, b 1 is the parameter estimate, and time is the number of days between tagging and recapture. Tag returns from double-tagged fish were assigned a dummy variable of 1 to indicate a single tag loss or 2 to indicate no tag loss. The dummy variables and associated estimates of time at large (time) for tag returns from double-tagged fish tagged in each period (P) were then used in Procedure LOGISTIC (SAS 1996) to calculate estimates of a and b 1 for each tagging period. Once the parameter estimates were obtained for equation 1, I estimated the logistic probability of tag loss (logit(l)) for each tagging period and year based on the average time fish from a given tagging period (P) were at large in year (y). These logistic probabilities were then used in the following equation to calculate the probability of a single tag loss (p) for fish tagged in period P and recaptured during year y (Miranda et al. 1997): peelllogit()logit()1 (2) I assumed that all tag loss events were independent and subsequently estimated the probability of a fish losing two tags as the square of the probability of a single tag loss

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10 (p 2 ). Estimates of p and p 2 were then subtracted from 1 to predict tag retention rates for single-tagged fish (1-p) and double-tagged fish (1-p 2 ). The total number of single-tagged (N single ) and double-tagged (N double ) fish from each tagging period and year were then adjusted based on their respective retention rates. Tag-related mortality was estimated based on the results of a cage study, which was conducted within the reservoir. A 2-m x 1-m x 1-m cage with 10-cm plastic bar mesh was used to hold 3 to 16 fish per cage trial. Six to nine cage trials were conducted per tagging period with each trial lasting a minimum of 40-hours. All cage trials were conducted in Area 3 (Figure 1) of the reservoir. At the end of each trial fish were checked for survival and released. Trials were conducted using fish captured via electrofishing (trials = 11) as well as those collected at tournaments (trials = 4). The total number of tagged fish were separated by capture method and tagging period, adjusted for the appropriate tag-related mortality rate, and recombined. Reporting rates of high-dollar reward tags in 2001 were estimated based on a linear-logistic model created by Nichols et al. (1991): HHee000450028300045002831.... H (3) where H is the dollar value of a fish tagged with a high-dollar reward (i.e., $50, $55, or $100) and H is the reporting rate of tags from high-reward fish. This model was originally created to estimate the reporting rate of duck bands based on the monetary reward value of the band. Because the model was created in 1988, the reward values (H) were converted from 2001 standards to the 1988 monetary equivalents based on the Consumer Price Index (Nichols et al. 1991). The 1988 monetary equivalents used in equation 3 were $33.40, $36.71, and $66.80 for $50, $55, and $100 rewards, respectively

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11 (U.S. Department of Labor 2002). Reporting rate estimates calculated from equation 3 were most precise at high-reward values (Nichols et al. 1991). Therefore, I used equation 3 to estimate reporting rates of high-reward fish then calculated the reporting rate of low-reward tags based on the assumption that all tagged fish had an equal probability of recapture regardless of reward-value (equations 4 & 5). I estimated the total number of H reward fish caught (C H ) from the reservoir in 2001 using the following equation: CRHHH (4) where R H is the number of tags returned in 2001 from fish tagged with a high-reward. Equation 4 was repeated for all values of H. I then estimated the number of low-reward fish caught (C L ) from the reservoir in 2001 using the following ratio: CTCT5050LL (5) where L is the dollar value of a fish tagged with a low-reward (i.e., $5, $10), C 50 is the estimated number of $50-reward fish caught from the reservoir, and T 50 and T L are the original number of fish tagged with a $50-reward and a low-reward (L) respectively, adjusted for the appropriate rates of tag loss (p, p 2 ) and tagging mortality. Equation 5 was repeated for all values of L. I then substituted R L (the number of tag returns from low-reward value fish) and C L into equation 4 to estimate a reporting rate for low-reward fish ( L ) in 2001. This process was repeated for all low-reward values (i.e., $5 and $10). Reporting rate estimates for all reward values were varied by 50% to simulate possible error associated with the reporting rate estimates.

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12 Total annual catch (TAC) and total quarterly catch (TQC) of largemouth bass in 2001 were calculated as follows: TACCCTT20012001200111 LHLPH,P,, (6) TQCCCTTCCqqqii,,,,,,,,,2001200120012001200111 LHL,PHPLH (7) where 2001 denotes the year in which the fish were caught, P 1 denotes the period in which the fish were tagged (i.e., P 1 = period 1), q represents the quarter in which the fish were caught (i.e., q 1 = January 1 st to March 31 st q 2 = April 1 st to June 30 th etc.), and i represents all quarters previous to q within 2001. Due to time constraints, I was unable to obtain a full year of tag return data for 2002 and therefore unable to estimate reward-specific reporting rates for 2002. However, assuming that reporting rates did not vary significantly between years, I was able to use the 2001 reporting rate estimates to calculate an estimate of the total number of largemouth bass per reward value caught (C H,q,2002 C L,q,2002 ) from the reservoir in the first three quarters of 2002 (equation 4). Quarterly estimates of C H and C L were then used to estimate TQC of largemouth bass in 2002. TQCCCTTCCqqqii,,,,,,,,,20022002200220022002 X LHLHPLH (8) XvTTCC LPH, PLH,,1120012001 (9) where 2002 denotes the year in which fish were caught, i represents all quarters previous to q within 2002, and X is a correction term that accounts for the reduced number of season-1 fish present in the population at the start of 2002 due to natural mortality (v)

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13 (see below) and tag removal in the previous year. Equation 9 assumes that all tags were removed from fish caught by an angler in 2001, regardless of fate. Angler harvest of tagged fish during the last month of the fourth quarter of 2001 and the entire first quarter of 2002 was limited by the temporary 610-mm minimum length limit placed on the largemouth bass fishery during the 2001/2002 reservoir drawdown. Total harvest of largemouth bass per reward value (H L H H ) was estimated by adjusting the number of fish reported by anglers as harvested for non-reporting. Tag returns from fish with an unknown fate were divided proportionally among the known fate groups prior to reporting rate adjustments. Estimates of H L and H H were used in equation 6 in place of C L and C H to estimate total annual exploitation (u) (Ricker 1975) of largemouth bass in 2001. The total annual exploitation rate was then subtracted from the total annual catch rate to estimate the total annual catch and release rate for the reservoir. Age-and-Growth Data from the timed electrofishing transects was used to estimate total annual mortality and gender-specific growth rates. I created a gender-specific age length key from the subsampled largemouth bass collected during January 2002. Age-1 largemouth bass of unknown gender were randomly assigned a gender based on the assumption that sexually dimorphic growth rates are not evident in largemouth bass until age-2 (Schramm and Smith 1987). I used a gender-specific age length key to assign a gender and age to each individual in the whole sample (all fish captured during timed electrofishing transects, January 2002). Gender-specific age frequencies were calculated and a catch curve was fit for each gender. Age-1 fish were not included in the catch curve because these fish had not fully recruited to the gear (Bayley and Austen 2002). Due to a low sample size of older fish (< 5 fish per age-class over the age of 6) weighted catch curves

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14 were fit to age-frequency plots. The instantaneous rate of total mortality (Z) was estimated from the slope of the catch curve for each gender (Ricker 1975). I used the following equations to estimate total annual mortality (A) and the annual rate of natural mortality (v) for each gender (Ricker 1975): Az1e (10) v Au (11) I used the following equations to estimate mean-length-at-age (MLA) and variance ( 2 ) for each gender (DeVries and Frie 1996): MLAfxfii (12) 2221ffxfxffiiiii (13) where x is a given centimeter group and f i is the number of gender i fish of a given age in centimeter group x. I used the von Bertalanffy growth model (Ricker 1975) to describe gender-specific growth rates: MLALekt10(age ) (14) Parameter estimates (L k, t o ) were obtained for equation 14 using Procedure NLIN (SAS 1996) and were based on previously calculated estimates of mean-length-at-age (equations 12 & 13). The growth models were used to estimate mean total-length-at-age (TLA) for each gender. Weight-length equations were created for male and female largemouth bass at Rodman Reservoir based on the subsample of fish collected in 2002 (Ricker 1975):

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15 W L ba (15) where W is the weight of the fish, L is the length of the fish, a is the intercept, b is the shape parameter. Parameters were estimated from the log e transformed model: log()loglog()WL ab (16) Regulation Simulations I used the Inland Fisheries Regulation Simulator (IFREGS) model described by Allen and Miranda (1998) to simulate the response of the fishery to four minimum length limits; 254-mm TL, 356-mm TL, 457-mm TL, and 510-mm TL, three slot limits; 381-510-mm TL, 381-559-mm TL, and 381-610-mm TL, a maximum length limit; 457-mm TL, and a complete catch and release regulation. The model required estimates of gender-specific total length-at-age, gender and age specific rates of exploitation and natural mortality, and parameter estimates from gender-specific weight-length equations to forecast the annual age-structure of the population under a given harvest restriction. Gender-specific estimates of mean TL-at-age were obtained from the von Bertalanffy growth models (equation 14). Estimates of TL-at-age were used to describe annual incremental growth. Within year growth was assumed to be linear. Gender and age specific exploitation rates were obtained by calculating length specific exploitation rates for quality (300-379 mm TL), preferred (380-509 mm TL), and memorable (510+ mm TL) size fish (Anderson and Neumann 1996) and assigning these exploitation rates to each gender based on mean total-length-at-age (equation 14). Gender and age specific natural mortality rates were obtained by subtracting the gender and age specific exploitation rates from total annual mortality (equation 11) and the parameter estimates for the gender-specific weight-length equations were obtained from equation 15.

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16 Gender and age specific exploitation rates were used to estimate total harvest (fish 254-mm TL) and harvest of quality, preferred, and memorable size fish. Gender and age specific natural mortality estimates were combined with exploitation estimates to describe total annual mortality and to predict the number of fish in the population each year. The parameter estimates from the gender-specific weight-length equations were used to transform fish lengths to fish weights in order to predict the annual biomass of the population. The model simulated length limits by protecting fish from harvest if they were below a minimum length limit or within a slot limit. The model assumed that all fish 254-mm TL were susceptible to harvest if they were not protected by a regulation. I ran each simulation for 50-years with 1000 fish recruiting to age-1 (500-males, 500-females). I used the predicted number of quality, preferred, and memorable size fish harvested as well as the predicted total number of fish harvested from the 50 th simulation year to compare the effectiveness of each regulation for maximizing harvest. Estimates of overall total catch (all fish 254-mm TL) and total catch of quality, preferred, and memorable size fish were calculated based on the age structure predicted for the 50 th simulation year under a given harvest restriction. Gender and age specific total catch rates applied to the age structures were obtained by calculating length-specific exploitation rates for quality, preferred, and memorable size fish and assigning these catch rates to each gender based on mean TL-at-age. The predicted age structure for the 50 th simulation year under each harvest restriction was then multiplied by the appropriate total catch rates to obtain estimates of overall total catch and total catch of quality, preferred, and memorable size fish.

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17 In order to account for potential error associated with my reporting rates, all simulations were repeated using gender-specific exploitation and natural mortality rates associated with 50% variability in reporting rate. Previous studies that used multiple methods (e.g., postcard surrogates, phone interviews, creel surveys, or surreptitiously implanted tags) to estimate reporting rates have shown reporting rate variability to range from 11% to 52% (Larson et al. 1991; Maceina et al. 1998; Miranda et al. 2002). Therefore, simulations that used mortality estimates associated with 50% variation in reporting rate accounted for potential high variability in my reporting rate estimates. Simulation results were compared to identify inconsistencies that would result from incorrectly estimating the reporting rate of tags.

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RESULTS Tagging Study Tagging-period one ran from November 28, 2000 to March 31, 2001, 50 sampling trips were made to the reservoir during this time. Forty-four trips were dedicated to electrofishing and the remaining 6 trips were spent tagging fish collected at tournaments. A total of 1,368 largemouth bass were tagged during tagging period-1, 1,014 of these fish were collected by electrofishing, and 354 fish were collected at tournaments. Tagging period two ran from November 10, 2001 to January 9, 2002, 15 sampling trips were made to the reservoir during this time. Fourteen of these trips were spent electrofishing and the remaining trip was spent tagging fish at a tournament. A total of 1,270 largemouth bass were tagged during period-2, 1,258 of these fish were collected by electrofishing and the remaining 12 were collected at a tournament. Electrofishing catch rates were higher in tagging period-2 this was likely due to the reservoir drawdown. A summary of the number of fish tagged per period and reward value is presented in Table 1. About half of the fish were tagged with $5 reward tags in both tagging periods. A low number (n = 6) of $55 reward fish were released during period-1. A total of 406 and 486 largemouth bass were double-tagged (reward value = $10, $55, $100) during periods 1 & 2, respectively (Table 1). Annual tag loss rates for single and double tagged fish are presented in Table 2. Fish tagged in period-1 were at large an average of 87 days (range = 1 to 337 days) before recapture in 2001 and 421 days (range = 329 to 528 days) before recapture in 18

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19 2002. Fish tagged in period-2 were at large and average of 66 days (range = 0 to 250 days) before recapture in 2002 (Table 2). Based on the period tagged and the average time at large, tag loss ranged from 4% to 26% for single-tagged fish and from 0.2% to 6.6% for double-tagged fish (Table 2). Tag loss was positively related to time at large. Cage trials were conducted during both tagging periods, 9 trials (6 electrofishing trials, 3 tournament trials) were conducted in 2001 and 6 in 2002 (5 electrofishing trials, 1 tournament trial). On average 10 fish (range = 3 to 16) were caged per trial and each trial lasted an average of 50 hours (range = 43 to 79). A total of 145 fish were caged over the course of the study, all of which survived, resulting in a tag related mortality rate of 0%. Therefore, the original number of fish (N) tagged in each period did not have to be adjusted for tagging mortality. An estimated 1,314 tagged fish from period-1 remained in the reservoir after tag loss in 2001 and about 1,246 tagged fish from period-2 remained after tag loss in 2002. Period-1 fish present in the reservoir in 2002 were adjusted for tag loss (p = 0.2576, p 2 = 0.0663) based on an average of 421 days at large. They were also adjusted for natural mortality v = 0.38 (described below) and angler removal of tags (n = 546) in 2001. Based on these adjustments I estimated that 382 largemouth bass tagged in period-1 were present in the reservoir in 2002 (Table 1). Tag returns were collected from January 1, 2001 to September 30, 2002. Tags from 260 fish were returned in 2001 and tags from 231 fish were returned in the first three quarters of 2002. During 2001, the percent return of tags ranged from 16% ($5 reward) to 33% ($55 reward) (Table 1). Estimated reporting rates were positively correlated with monetary reward values and ranged from 39% ($5 reward) to 87% ($100 reward) (Table 1).

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20 During 2001, 67 tagged fish were reported by anglers as harvested and 180 tagged fish were reported as released. During the first three quarters of 2002, 24 tagged fish were reported by anglers as harvested and 203 were reported as released. Thirteen fish had an unknown fate in 2001 and 4 fish had an unknown fate in 2002. These fish were divided among the known-fate categories (i.e., kept or released) based on the proportion of fish in each reward category that were reported as kept or released. Total annual catch, annual exploitation, and annual catch and release rates for largemouth bass in 2001 were 0.42, 0.11, and 0.31, respectively. Thus, about 26% (i.e., 0.11 / 0.42 = 0.26) of the largemouth bass caught from the reservoir in 2001 were harvested and about 74% were released. Tag returns from 2002 showed that the total catch, exploitation, and catch and release rates for the first three quarters of 2002 were 0.30, 0.03, and 0.27, respectively, indicating that about 90% of the fish caught in the first three quarters of 2002 were released. Length-specific estimates of exploitation, total catch, and natural mortality were calculated for 2001 based on three length categories; quality (356-379-mm TL), preferred (380-509-mm TL), and memorable ( 510-mm TL). Annual exploitation rates of quality, preferred, and memorable fish were 0.08, 0.12, and 0.20, total annual catch rates were 0.38, 0.42, and 0.40, and natural mortality rates were 0.41, 0.37, and 0.29, respectively. Anglers harvested 22%, 28%, and 50% of all the quality, preferred, and memorable size fish, respectively, that were caught in 2001. Regulations during the first year of the tagging study (2001) prevented anglers from harvesting fish < 356-mm TL, because these fish were protected from harvest (u = 0) estimates of exploitation, total annual catch, and natural mortality used in the simulation models for fish 254-355-mm TL were therefore

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21 based on the calculated exploitation (u = 0.08), total annual catch (TC = 0.38), and natural mortality (v = 0.41) rates associated with quality sized fish. Altering reporting rate estimates by 50% to account for possible variability associated with the reporting rate estimates affected the estimates total annual catch, exploitation, and natural mortality. Increasing reporting rate estimates by 50% resulted in lower estimates of total annual catch and exploitation and a higher estimate of natural mortality, reducing reporting rates by 50% had opposite effects. Increasing reporting rates by 50% resulted in total annual catch rates of 0.26, 0.28, and 0.28, annual exploitation rates of 0.06, 0.08, and 0.14, and natural mortality rates of 0.43, 0.41, and 0.35 for quality, preferred, and memorable size fish, respectively. Decreasing reporting rates by 50% resulted in total annual catch rates of 0.76, 0.83, and 0.82, annual exploitation rates of 0.17, 0.23, and 0.41, and natural mortality rates of 0.32, 0.26, and 0.08 for quality, preferred, and memorable size fish, respectively. Quarterly tag returns were used to estimate total quarterly catch of largemouth bass in all quarters of 2001 and in the first three quarters in 2002. TQC rates ranged from 3% (Quarter-3, 2002) to 22% (Quarter-2, 2001) (Table 3). TQC rates in the first (TQC = 16%) and second (TQC = 22%)) quarters of 2001 were higher than TQC rates in the third (TQC = 7%)) and fourth (TQC = 3%)) quarters of 2001, indicating a decline in catch after June 30, 2001. The TQC rate of largemouth bass in the first quarter of 2001 (16%) was less than the TQC rate in the first quarter of 2002 (20%) (Table 3). Additionally, TQC rates in the second (22%) and third (7%) quarters of 2001 were higher than TQC rates in the second (10%) and third (3%) quarter of 2002 (Table 3).

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22 This chapter discusses what a style is, how it is applied, and how it should be used to create your thesis or dissertation. Age-and-Growth Seventeen 20-minute electrofishing transects and one 10-minute electrofishing transect were conducted from January 7, 2002 to January 9, 2002. A total of 1,239 largemouth bass were collected and measured (whole-sample). Three hundred and twenty two largemouth bass (sub-sample) collected during sampling efforts, ranging from 80-603 mm TL, were returned to the laboratory to be measured, weighed, and gender and age determined. Female largemouth bass in the whole sample did not exceed 600-mm TL, whereas males did not exceed 530-mm TL. Female largemouth bass reached a mean length of 587 20-mm TL by age-10, whereas male largemouth bass reached a mean length of 435 6-mm TL by age-10 (Figure 2). Gender specific values of number-at-age were used for catch curve analysis. Age classes 7, 9, and 10 were underrepresented (< 5 fish) for both, male and female largemouth bass. No eight year-old fish were collected. Gender specific rates of total annual mortality calculated from the slopes of the catch curves were 0.46 and 0.51 for male and female largemouth bass, respectively. Analysis of covariance showed that there were no significant differences between the slopes (p = 0.6473) or y-intercepts (p = 0.8200) of the gender-specific catch curves, indicating that total annual mortality was not significantly different between genders. Thus, gender-specific number-at-age values were pooled and catch curve analysis was repeated for the pooled sample (Figure 3). Total annual mortality for all fish was 0.49. Length-specific estimates of natural mortality mentioned above were calculated based on length-specific exploitation rates and the pooled estimate of total annual mortality (equation 11). Lengths and weights

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23 pertaining to the sub-sampled fish were used to create the following gender-specific weight-length equations for male (equation 20) and female (equation 21) largemouth bass, respectively: W4421063207.. LL (20) W4661063196.. (21) Regulation Simulations Results of the simulations are summarized in Figures 4 and 5. Total annual harvest of largemouth bass 254-mm TL and total harvest of quality-sized fish were greatest under a 254-mm minimum length limit (Figure 4A & 4B). Total harvest of preferred-sized fish was greatest under a 356-mm minimum length limit (Figure 4C) and total harvest of memorable-sized fish was greatest under a 510-mm minimum length limit (Figure 4D). Overall total catch and total catch of preferred and memorable sized fish were greatest under a catch and release regulation (Figure 5A, 5C, and 5D). The 510-mm minimum length limit resulted in the second highest overall total catch and total catch of preferred and memorable sized fish (Figure 5A, 5C, and 5D). The 457-mm minimum length limit, the 510-mm minimum length limit, and the catch and released regulation all maximized the total catch of quality-sized fish (Figure 5B). Assuming anglers would not harvest fish < 254-mm TL, simulating the effects of a 254-mm minimum length limit on the fishery was essentially equivalent to simulating no length limit. Using this regulation as a benchmark to identify the success of alternate harvest restrictions revealed that the catch and release regulation, the 510-mm minimum length limit, and the 457-mm minimum length limit were the top three regulations for maximizing the overall total catch of largemouth bass as well as the total catch of quality,

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24 preferred, and memorable size fish. The catch and release regulation yielded the highest increase in total catch, increasing the overall total catch by 32% and increasing the total catch of quality, preferred, and memorable sized fish by 8%, 54%, and 103%, respectively compared to no length limit. The 510-mm minimum length limit was the next most effective regulation for maximizing total catch, increasing the overall total catch by 18% and increasing total catch of quality, preferred, and memorable sized fish by 8%, 46%, and 100%, respectively. The 457-mm minimum length limit followed with a 17% increase in the overall total catch and an 8%, 41%, and 77% percent increase in the total catch of quality, preferred, and memorable size fish, respectively. Simulations based on exploitation and natural mortality rates associated with 50% error in reporting rate showed similar trends with regards to overall total harvest, total harvest of preferred and memorable sized fish, overall total catch, and total catch of quality, preferred, and memorable sized fish. However, simulation results associated with a 50% increase in reporting rate estimates showed that several regulations (254-mm minimum length limit, 457-mm maximum length limit, 381-510 mm slot limit, 381-559 mm slot, and 381-610 mm slot) would maximize total harvest of quality-sized fish.

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25 Figure 1. Rodman Reservoir located in Putnam and Marion Counties, Florida. Areas 1-4 represent designated capture and release areas for the tagging study. 1234 4048Kilometers NPayne's Landing Orange Springs Kenwood Landing Kirkpatrick DamB a r g e C a n a lSR 19 Bridge Tournament Release Area

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26 MLAFemalesage68310210200035..(.)e 70 60 50 Length (mm) 40 30 20 MLAMalesage46010352501374..(.)e 10 0 0 1 2 3 4 5 6 7 8 9 10 Age Figure 2. Von Bertalanffy growth models fit to mean-length-at-age values for male (triangles) and female (squares) largemouth bass collected from Rodman Reservoir in January 2002.

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27 All Fish11010010001990199219941996199820002002Year Classln number of fishy = -0.68(x) + 7.45Z = -0.68 A = 0.49 Figure 3. Weighted catch curve based on number-at-age data for all fish collected during electrofishing transects conducted at Rodman Reservoir in January 2002. Total annual mortality of largemouth bass was 49%. A weighted catch curve was fit to the data because the 1992 to 1995 year-classes were underrepresented ( 5 fish).

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28 D C B A Regulation Numbe r Harvested Memorable 381-610 Slot 381-559 Slot 381-510 Slot 457 MAX 510 MIN 457 MIN 356 MIN 254 MIN 15 10 5 0 Preferred 381-610 Slot 381-559 Slot 381-510 Slot 457 MAX 510 MIN 457 MIN 356 MIN 254 MIN 40 30 20 10 0 Quality 381-610 Slot 381-559 Slot 381-510 Slot 457 MAX 510 MIN 457 MIN 356 MIN 254 MIN 40 30 20 10 0 Total Harvest 381-610 Slot 381-559 Slot 381-510 Slot 457 MAX 510 MIN 457 MIN 356 MIN 254 MIN 80 60 40 20 0 Figure 4. Estimated annual harvest of all fish 254-mm (A) and quality (300-379-mm) (B), preferred (380-509-mm) (C), and memorable ( 510-mm) (D) sized fish based on 50-year simulations run in IFREGS. All estimates are based on 1,000 fish recruiting to age-1.

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29 Total Catch 400 Numbe r Caught D C B A 350 300 250 254 MIN 356 MIN 457 MIN 510 MIN 457 MAX 381-510 Slot 381-559 Slot 381-610 Slot Catch & Release Quality 150 140 130 120 254 MIN 356 MIN 457 MIN 510 MIN 457 MAX 381-510 Slot 381-559 Slot 381-610 Slot Catch & Release Preferred 140 120 100 80 60 254 MIN 356 MIN 457 MIN 510 MIN 457 MAX 381-510 Slot 381-559 Slot 381-610 Slot Catch & Release Memorable 30 20 10 0 254 MIN 356 MIN 457 MIN 510 MIN 457 MAX 381-510 Slot 381-559 Slot 381-610 Slot Catch & Release Regulation Figure 5. Estimated annual catch of all fish 254-mm (A) and quality (300-379-mm) (B), preferred (380-509-mm) (C), and memorable ( 510-mm) (D) sized fish based on 50-year simulations run in IFREGS. All estimates are based on 1,000 fish recruiting to age-1.

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Table 1. Estimated catch of 2,638 largemouth bass tagged and released at Rodman Reservoir, Florida. The adjusted numbers of tagged fish were corrected for tag loss (p & p 2 ) and tagging mortality (0%). Period-1 adjusted tagged fish in 2002 were also corrected for natural mortality and angler removal of tags during 2001. Tag returns were adjusted for non-reporting to obtain estimated catch. Tagging Period Recapture Year Value Tagged Tag Loss Adjusted Tagged Number Returned Percent Returned Reporting Rate Estimated Catch (P) (y) ($) (N) (p, p 2 ) (T) (R) (%) () (C) 1 2001 5 739 0.0557 698 113 16 0.3893 290 1 2001 10* 400 0.0031 399 82 21 0.4944 166 1 2001 50 223 0.0557 210 63 30 0.7192 88 1 2001 55* 6 0.0031 6 2 33 0.7379 3 Total: 1,368 1,313 260 20% 547 Percent: 42% 1 2002 5 739 0.2576 188 23 12 0.3893 59 1 2002 10* 400 0.0663 135 23 17 0.4944 46 1 2002 50 223 0.2576 57 18 32 0.7192 25 1 2002 55* 6 0.0663 2 0 0 0.7379 0 Total: 1,368 382 64 130 Percent: 34% 30

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31 Table 1. Continued Tagging Period Recapture Year Value Tagged Tag Loss Adjusted Tagged Returned Percent Returned Reporting Rate Estimated Catch (P) (y) ($) (N) (p, p 2 ) (T) (R) (%) () (C) 2 2002 5 686 0.0438 656 76 12 0.3893 195 2 2002 10* 400 0.0019 399 50 13 0.4944 101 2 2002 50 104 0.0438 99 23 23 0.7192 32 2 2002 55* 50 0.0019 50 10 20 0.7379 14 2 2002 100* 30 0.0019 30 8 27 0.8650 9 Total: 1,270 1,234 167 351 Percent: 28% Indicates that the fish were tagged with two tags (double-tagged).

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32 Table 2. Tag loss rates for single-tagged (p) and double-tagged (p 2 ) largemouth bass at Rodman Reservoir. Tag loss was estimated based on electrofishing and angler recaptures of double-tagged fish. Proc LOGISTIC (SAS 1996) was used to obtain intercept (a) and parameter (p) estimates for tag loss models: logit() = labtime1() Tagging Recapture Parameter Average Tag Loss Period Year Intercept Estimate Time Single Tag Double Tag (P) (y) (a) (b 1 ) (tij) (p) (p 2 ) 1 2001 -3.2904 0.0053 86.93 0.0557 0.0031 1 2002 -3.2904 0.0053 421.09 0.2576 0.0663 2 2002 -3.7512 0.0101 66.08 0.0438 0.0019

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33 Table 3. Quarterly catch rates of tagged fish caught from Rodman Reservoir during the first 3 quarters of 2001 and 2002. Adjusted tagged fish were corrected for tag loss (p & p 2 ), tagging mortality (0%), and angler removal of tags (C). Fish tagged in period-1 and recaptured in 2002 were adjusted for natural mortality (v = 38%). Returns were adjusted for non-reporting to estimate catches (C). Quarter Recapture Year Value Adjusted Tagged Number Returned Percent Returned Estimated Catch Percent Caught (q) (y) ($) (T) (R) (%) (C) (%) 1 2001 5 698 42 6 108 15 1 2001 10 399 31 8 63 16 1 2001 50 210 30 14 42 20 1 2001 55 6 1 17 1 23 Total 1,313 104 214 Percent 8% 16% 2 2001 5 590 48 8 123 21 2 2001 10 336 41 12 83 25 2 2001 50 168 28 17 39 23 2 2001 55 5 0 0 0 0 Total 1,099 117 245 Percent 11% 22% 3 2001 5 467 17 4 44 9 3 2001 10 253 7 3 14 6 3 2001 50 129 1 1 1 1 3 2001 55 5 1 22 1 29 Total 854 26 60 Percent 3% 7%

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34 Table 3. Continued Quarter Recapture Year Value Adjusted Tagged Number Returned Percent Returned Estimated Catch Percent Caught (q) (y) ($) (T) (R) (%) (C) (%) 1 2002 5 844 67 8 172 20 1 2002 10 534 49 9 99 19 1 2002 50 156 23 15 32 20 1 2002 55 52 5 10 7 13 1 2002 100 30 7 23 8 27 Total 1,616 151 318 Percent 9% 20% 2 2002 5 672 27 4 69 10 2 2002 10 435 18 4 36 8 2 2002 50 124 15 12 21 17 2 2002 55 45 5 11 7 15 2 2002 100 22 0 0 0 0 Total 1,298 65 133 Percent 5% 10% 3 2002 5 603 5 1 13 2 3 2002 10 399 6 2 12 3 3 2002 50 103 3 3 4 4 3 2002 55 38 0 0 0 0 3 2002 100 22 1 5 1 5 Total 1,165 15 30 Percent 1% 3%

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DISCUSSION The optimal harvest restriction for the reservoir should provide the best combination of overall total catch and total catch of large fish, while catering to angler preferences. The top three regulations for improving overall total catch and total catch of memorable-sized fish were (1) the catch and release regulation, (2) the 510-mm minimum length limit, and (3) the 457-mm minimum length limit. In 2001, anglers harvested memorable-sized largemouth bass at a much higher rate than smaller fish, thus eliminating harvest with a catch and release regulation may interfere with preferences of some angler groups. A catch and release regulation would also prevent tournaments from taking place at the reservoir because tournament exemptions are prohibited under a catch and release regulation (FFWCC). During the 2001 fiscal-year, the FFWCC granted tournament exemptions at Rodman Reservoir to 37 tournament groups which involved 1,018 tournament anglers (W. Chamberlain, FFWCC, unpublished data). Eliminating the ability to hold future tournaments by instating a catch and release regulation, would therefore conflict with a substantial number of tournament anglers. Due to the potential conflicts with angler groups, managers should consider alternatives to the catch and release regulation. The 510-mm minimum length limit and the 457-mm minimum length limit were the next best regulations for maximizing overall total catch and the total catch of memorable-sized fish. In addition, the 510-mm and 457-mm minimum length limits were the most effective regulations for maximizing harvest of memorable-sized fish. 35

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36 Both regulations had a similar effect on the total catch of largemouth bass, however the total harvest of memorable-sized fish under the 510-mm minimum length limit was 22% (range: 20% to 50%) higher than total harvest of memorable-sized fish under the 457-mm minimum length limit. Therefore, the 510-mm minimum length limit would at least be equivalent to if not better than the 457-mm minimum length limit. I suggest that managers should consider implementing a 510-mm minimum length limit at Rodman Reservoir. However, should managers have difficulty instating the 510-mm minimum length limit because the regulation has not been previously approved for use by the FFWCC, the 457-mm minimum length limit would serve as a suitable alternative. This length limit has been previously used by the FFWCC to regulate largemouth bass fisheries within Florida, and it is the next most effective regulation for maximizing overall total catch and total catch and harvest of memorable-sized fish. Estimates of annual exploitation used in the simulation models were based on 2001 tag returns and ranged from 8% (quality fish) to 20% (memorable fish). A review of mortality rates associated with 30 largemouth bass populations in the United States showed annual exploitation rates to range from 9-72% (average u = 36%) (Allen et al. 1998). Based on these findings the exploitation rates of largemouth bass at Rodman Reservoir appear to be low compared to historical data in the United States. Despite the low rates of exploitation, exploitation rates were positively related to fish length, indicating a preference among angler to harvest large fish. The total annual mortality rate used in the simulations was 49%. Allen et al. (1998) reviewed mortality estimates for 30 largemouth bass populations in the United States and found total annual mortality rates to range from 24-92% (average A = 64%). Allen et al.

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37 (2002) calculated a 51% average total annual mortality rate for largemouth bass in 45 Florida water bodies. The total annual mortality rate of largemouth bass at Rodman Reservoir was slightly lower than the national average but similar to the average total annual mortality of largemouth bass in Florida waters. Gender-specific mean total-length-at-age estimates used in the simulations predicted that male largemouth bass would not exceed a mean total length of 443-mm, thus precluding males from contributing to the memorable-size portion of the population. Only one male largemouth bass was collected in excess of 510-mm TL during age-and-growth sampling, therefore males did not contribute greatly to the memorable-size portion of the population. Regulations that restrict harvest of fish < 510-mm TL will therefore focus the majority of the harvest on the female portion of the population. Managers should be aware that focusing the majority of harvest on one gender could eventually skew the sex ratio of the population. Female largemouth bass at Rodman Reservoir reached memorable size between ages 6 and 7 and reached an average weight of 2.2-kg by age-11. A previous study by Allen et al. (2002) examined gender-specific growth rates for 35 largemouth bass populations in Florida lakes and found that female largemouth bass with average growth reached memorable size between ages 6 and 7. Therefore, female growth rates at Rodman Reservoir were about average in comparison to other Florida water bodies. According to the FFWCC Big Catch program a largemouth bass must be 610-mm TL or 3.6-kg to be considered a trophy catch. Average growth rates at Rodman Reservoir do not produce trophy fish, thus memorable-sized fish were used as a gauge to measure

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38 each regulations effectiveness at increasing the number of large fish ( 510-mm TL) within the reservoir. Results of the tagging study showed that tag retention rates declined with increasing time at large. Retention rates ranged from 96% (66 days at large) to 74% (421 days at large), based on the average number of days fish were at large. Renfro et al. (1995) found 100% tag retention in largemouth bass that were tagged and held in hatchery ponds for 3-months, and 98% average retention (range: 93% to 100%) for largemouth bass that were tagged and held in sample ponds for 15-months, using the same tags used in this study. Renfro et al. (1995) did not find retention rates to decrease with increasing time at large. Retention rates calculated in this study were lower than those calculated by Renfro et al. (1995). The individual error associated with fish tagging was compounded by the high number of individuals (N = 25) that participated in tagging efforts and may have contributed to the high level of tag loss observed in this study. Additionally, anglers may have intentionally or inadvertently misreported the presence of two tags in follow-up phone interviews. Conversations with anglers revealed a common belief that both tags should not be removed from double-tagged fish. Some anglers believed that it was wrong to remove both tags, while others believed they were contributing to the success of the study by not removing all tags. In either case, misreporting a tag loss from a double-tagged fish would have inflated my estimate of tag loss. In response to this apparent confusion among anglers, signs were posted at boat ramps in January 2002, indicating that all tags should be removed from double-tagged fish (Appendix 3). Tag retention rates may have been more comparable to those found

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39 by Renfro et al. (1995) had the angling community clearly understood how to treat double-tagged fish. Cage trials conducted during the fall and winter showed a 100% survival rate for tagged fish. This survival rate was comparable to the survival rates calculated in previous tagging studies (Tranquilli and Childers 1982; Renfro et al. 1995). Renfro et al. (1995) showed that over the course of a three-month pond study mortality rates of fish tagged with Halprint dart-style tags did not differ significantly from mortality rates of untagged fish. Tranquilli and Childers (1982) also showed 100% survival rate for tagged fish in a 191-day pond experiment. Tag returns may have suffered from a lack of independence. Pollock et al. (2001) suggested that anglers may have a tendency to collect low-reward tags until they gather enough tags to make them worth mailing. Anglers participating in this study commonly returned several tags at once indicating a possible lack of independence. The tag return envelopes used in this study may have also contributed to the lack of independence in tag returns. Tag return envelopes were not postage-paid therefore the cost and effort associated with mailing a single tag may have outweighed the reward, possibly leading anglers to accumulate tags until they had collected enough reward money to justify mailing in the tags. This possible lack of independence in tag returns may have inflated my reporting rate estimates. The exploitation rate of largemouth bass calculated for the first three quarters of 2002 was low (u 2002 = 3%) in comparison to the 2001 annual exploitation rate (u 2001 = 11%). Although the 2002 exploitation rate will increase as tags are returned from fish caught in the fourth quarter of 2002, I do not expect the exploitation rate to increase

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40 dramatically nor do I expect it to match or exceed the 2001 annual exploitation rate. The low exploitation rate in 2002 was probably due to (1) the 610-mm minimum length limit implemented during the 2001-2002 reservoir drawdown and (2) a possible decline in the return rate of tags from 2001 to 2002. The temporary 610-mm minimum length limit placed on the largemouth bass fishery during the drawdown period coincided with the first quarter of 2002 and protected the majority of the fish caught during that quarter from harvest. Because 66% of all the fish caught in the first three quarters of 2002 were caught during the first quarter of the year, the temporary length limit contributed to the lower exploitation rate in 2002. In addition, using 2001 reporting rate estimates to estimate total catch in 2002 may not have been appropriate since reporting rates have been shown to decline from the first year of the study to subsequent years (Dequine and Hall 1949; Moody 1960). If reporting rates declined from the first to second year of my study, the use of first year reporting rates would result in underestimates of exploitation and total catch in 2002. Reward-specific reporting rates were not calculated for 2002 because a complete year of tag return data was not available. Although 2002 reporting rates were not available, comparing the percent return of tags in the second (11%) and third (3%) quarters of 2001 to the second (5%) and third (1%) quarters of 2002 revealed a decline in the return rate of tags (Table 3). However, the percent return of tags in the first quarter of the year increased from 2001 (8%) to 2002 (9%) (Table 3). This increase may be an indication that tag return rates did not decline with increasing study length. Nevertheless, it is more likely that a decline in reporting rates occurred and was masked by an increase in angler catch rates associate with the reservoir drawdown. Therefore,

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41 angler catch rates calculated for the first three quarters of 2002 were probably underestimated, leading to an underestimate of exploitation and total catch for 2002. Harvest restrictions are often more effective at altering the age structure of populations that have additive mortality rates as opposed to compensatory (Allen et al. 1998). Changing exploitation rates in populations with additive mortality has a direct effect on total annual mortality. However, changing exploitation rates in populations with compensatory mortality may not effectively reduce total annual mortality. Growth and natural mortality of a population may also dictate the effectiveness of a regulation. Beamesderfer and North (1995) found that angler catch rates and the occurrence of large fish were likely to increase when harvest restrictions were applied to average (average growth, average v) or productive (fast growth, low v) populations. Conversely, they found that limiting exploitation of unproductive populations (slow growth, high v) may not be beneficial because many fish would die before they reached quality size. Compared to the populations studied by Beamesderfer and North (1995), growth rates and natural mortality of largemouth bass at Rodman Reservoir were average. Based on these findings and the assumption that mortality rates of largemouth bass were additive, harvest restrictions should serve as an effective means for manipulating the age structure of the largemouth bass population at Rodman Reservoir. Miranda et al. (2002) questioned the effectiveness of tagging studies as a means for accurately assessing exploitation rates. They reported that the variability associated with estimating reporting rates is so large that it precludes a managers ability to accurately assess exploitation, thus Miranda et al. (2002) recommended that managers seek an alternate means for estimating exploitation. Because my exploitation rates were derived

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42 from a tagging study, I introduced high error into my reporting rate estimates and used the associated exploitation and natural mortality rates in simulation models to verify that trends in the simulation results would remain constant regardless of the possible variability associated with my reporting rate estimates. Simulations using exploitation and natural mortality rates associated with 50% variability in reporting rate showed that trends in total catch remained constant. Trends in total harvest were moderately affected by the extreme variation in reporting rates. Overall, variability in exploitation due to reporting rate error did not significantly impact the relative value of each harvest restriction. The purpose of the simulation model was to identify trends in the populations response to various harvest restrictions. Simulation models have error associated with their estimates just as field data have associated error (Johnson 1995). Therefore, error associated with specific predictions of the simulation model my recommendation to implement a 510-mm minimum length limit at Rodman Reservoir was based primarily on the trends reveled by the simulations, not the specific values.

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FURTHER STUDY Several factors could interfere with the success of the proposed 510-mm minimum length limit. These factors include (1) a potential for reduced growth due to the proposed high minimum length limit, (2) a potential for increased fish removal during tournaments due to the re-opening of Buckman Lock, and (3) the potential elimination of the reservoir due an ongoing debate to remove of the Senator George Kirkpatrick Dam. The proposed high minimum length limit could potentially reduce the growth rates of largemouth bass at Rodman Reservoir, thus interfering with the success of the proposed regulation. Seidensticker (1994) found evidence that slow growth of largemouth bass began 5-years after a 406-mm minimum length limit was implemented at a Texas reservoir. I suggest conducting semi-annual age-and-growth surveys at the reservoir to assess the potential effects of the regulation on fish growth rates. Age-and-growth assessments would allow managers to identify potential problems as well as track the success of the regulation as a means for altering the age structure of the population. According to Allen and Pine (2000) the probability of detecting differences in the age structure of a population due to an altered harvest restriction was higher under 5-year evaluations than 3-year evaluations. Wilde (1997) concluded that data should be collected for a minimum of three years following the implementation of a regulation in order to detect differences. In either case, duration of evaluation was the key to determining the effects of a regulation on a population. Based on these finding, I suggest monitoring age-and-growth of the population periodically for 5-7 years. 43

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44 The re-opening of Buckman Lock could lead to an increase in the number of largemouth bass removed from the reservoir due to tournaments and potentially lead to an increase in total annual mortality. Buckman Lock connects Rodman Reservoir to the St. Johns River allowing boater access between the two water bodies. The lock is commonly used by tournament anglers participating in fishing tournaments held outside of the reservoir. Tournament anglers that lock through to fish the reservoir remove largemouth bass from the reservoir when they return to the St. Johns River for weigh-ins. Tournament anglers participating in tournaments outside of the reservoir do not release fish back into the reservoir, thus tournament anglers could potentially contribute to the total annual mortality of largemouth bass at Rodman Reservoir. Buckman Lock was closed for the duration of this study except for a brief period in December of 2001 when the lock was opened to allow anglers participating in the Citgo Bassmasters Eastern Open to fish the reservoir. Buckman lock re-opened for regular operation in October of 2002. Due to the re-opening of the lock, I recommend that managers assess effects of outside tournament anglers on the abundance of largemouth bass at Rodman Reservoir. If tournaments remove a significant number of fish, I suggest re-evaluating the harvest restriction to ensure that the 510-mm minimum length limit is still the optimal regulation for the reservoir. Finally, the potential elimination of the reservoir due to an ongoing debate to remove the Senator George Kirkpatrick Dam and restore the free flowing Ocklawaha River could completely negate the findings of this study. The US Forest Service has voiced its intention to initiate action by 2006 to restore the federal land which is currently submerged beneath the reservoir and abuts the Senator George Kirkpatrick Dam. The

PAGE 55

45 intentions of the US Forest Service would effectively result in the removal of the reservoir. However, in response to the US Forest Services intentions, the Save Rodman Reservoir advocacy group has voiced their plan to file suit against the US Forest Service, should the US Forest Service take action to remove the dam. Managers should consider the potential for dam removal when deciding whether to implement a new harvest restriction. As previously stated, the effects of the regulation may not be visible for five or more years, thus the removal of the dam could prevent the regulation from ever taking full effect and if the dam was removed, a re-assessment of the fishery would need to take place before a new optimal harvest restriction could be chosen. Managers should take caution and consider all of these potential problems prior to implementing a new harvest restriction.

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46 APPENDIX A REWARD SIGN-1 Reward sign posted at fishing access points ar ound Rodman Reservoir and at local tackle shops. R E W A R D $5 AND $50 Fishery biologists have tagged Largemouth bass in the Rodman Reservoir. To receive a reward of $5 or $50, you must cut the tag from the fish and mail the tag and the following information to the address listed below. Send the following information with each tag: NAME DATE CAUGHT ADDRESS APPROXIMATE CATCH LOCATION PHONE NUMBER APPROXIMATE FISH LENGTH SOCIAL SECURITY NUMBER* COMMENTS SIGNATURE *Needed to receive reward. Address information is also provided on the tag, and tag mailers are provided at local tackle shops for your convenience. Please mail tag and information to: Florida Fish and Wildlife Conservation Commission 7922 NW 71st St. Gainesville, FL 32653 (352) 392-9617 ext. 240

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47 APPENDIX B TAG-RETURN INVOICE Tagreturn invoice distributed to all anglers that returned largemouth bass tags. Please mail tag and information to: Florida Fish and Wildlife Conservation Commission 7922 NW 71st St. Gainesville, FL 32653 (352) 392-9617 ext. 240 INVOICE To: Florida Fish and Wildlife Conservation Commission 7922 NW 71st St. Gainesville, FL 32653 TO BE FILLED OUT BY ANGLER From: (Please Print) Name: Social Security Number: (Needed for reward) Address: Phone Number:( ) Approximate Fish Length (inches): Date Caught: Approximate Catch Location: Was Fish Kept or Released Comments: Tournament : Yes/No (Circle) Tournament Name: Weigh-in Location:

PAGE 58

APPENDIX C REWARD SIGN-2 Informational sign posted at fishing access points around Rodman Reservoir beginning January 2002. The sign was intended to alleviate confusion among anglers regarding the number of tags that should be removed from double-tagged fish. LARGEMOUTH BASS TAGS Please Cut All Orange Tags from Fish Regardless of Whether the Fish is Kept or Released. REWARDS: $5,$10,$50,$55,$100 Please mail Tags to: Florida Fish and Wildlife Conservation Commission 7922 NW 71 st Street. Gainesville, FL 32653 (352) 392-9617 ext. 240 48

PAGE 59

LIST OF REFERENCES Allen, M. S., and L. E. Miranda. 1998. An age-structured model for erratic crappie fisheries. Ecological Modeling 107:289-303. Allen, M. S., L. E. Miranda, and R. E. Brock. 1998. Implications of compensatory and additive mortality to the management of selected sportfish populations. Lakes & Reservoirs: Research and Management 3:67-79. Allen, M. S., and W. E. Pine III. 2000. Detecting fish population responses to a minimum length limit: effects of variable recruitment and duration of evaluation. North American Journal of Fisheries Management 20:672-682. Allen, M. S., W. Sheaffer, W. F. Porak, and S. Crawford. 2002. Growth and mortality of largemouth bass in Florida waters: implications for use of length limits. International Black Bass Symposium. Anderson, R. O., and R. M. Neumann. 1996. Length, weight, and associated structural indices. Pages 447-482 in B. R. Murphy and D.W. Willis, editors. Fisheries techniques, 2 nd edition. American Fisheries Society, Bethesda, Maryland. Bayley, P. B., and D. J. Austen. 2002. Capture efficiency of a boat electrofisher. Transactions of the American Fisheries Society 131:435-451. Beamesderfer, R. C. P., and J. A. North. 1995. Growth, natural mortality, and predicted response to fishing for largemouth bass and smallmouth bass populations in North America. North American Journal of Fisheries Management 15:688-704. Benton, J., and D. Douglas. 1994. Ocklawaha chain of lakes largemouth bass population studies. Pages 29-54 in Upper Ocklawaha River completion reports: 1991 to 1994. Florida game and freshwater fish commission fisheries research laboratory, Eustis, FL. Canfield, D. E. Jr., E. J. Schulz, and M. V. Hoyer. 1993. "To be or not to be"--The Rodman Reservoir controversy. Final report, Department of Fisheries and Aquaculture, Center for Aquatic Plants. University of Florida, Gainesville. Crawford, S., W. S. Coleman, and W. F. Porak. 1989. Time of annulus formation in otoliths of Florida largemouth bass. North American Journal of Fisheries Management 9:231-233. 49

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50 Dequine, J. F., and C. E. Hall, Jr. 1949. Results of some tagging studies of the Florida largemouth bass Micropterus salmoides floridanus (LeSueur). Transactions of the American Fisheries Society 79:155-166. DeVries, D. R., and R. V. Frie. 1996. Determination of age and growth. Pages 483-512 in B. R. Murphy and D.W. Willis, editors. Fisheries techniques, 2 nd edition. American Fisheries Society, Bethesda, Maryland. Hoyer, M. V., J. V. Shireman, and M. J. Maceina. 1985. Use of otoliths to determine age and growth of largemouth bass in Florida. Transactions of the American Fisheries Society 114:307-309. Johnson, B. L. 1995. Applying computer simulation models as learning tools in fisheries management. North American Journal of Fisheries Management 15:736-747. Larson, S. C., B. Saul, and S. Schleiger. 1991. Exploitation and survival of black crappies in three Georgia reservoirs. North American Journal of Fisheries Management 11:604-613. Maceina, M. J., P.W. Bettolli, S. D. Finely, and V. J. DiCenzo. 1998. Analyses of the sauger fishery with simulated effects of a minimum size limit in the Tennessee River of Alabama. North American Journal of Fisheries Management 18:66-75. Miranda, L. E., R. E. Brock, and B. S. Dorr. 1997. Growth, fishing, and natural mortality of crappies in Mississippi. Pages 56-70 in Miranda, L. E., M. S. Allen, R. E. Brock, K. M. Cash, B. S. Dorr, L. C. Issak, and M. S. Schorr. Evaluation of regulations restrictive of crappie harvest. Mississippi Cooperative Fish and Wildlife Research Unit. Mississippi State University, Starkville. Miranda, L. E., R. E. Brock, and B. S. Dorr. 2002. Uncertainty of exploitation estimates made from tag returns. North American Journal of Fisheries Management 22:1358-1363 Moody, H. L. 1960. Recaptures of adult largemouth bass from the St. Johns River, Florida. Transactions of the American Fisheries Society 89(3):295-300. Nichols, J. D., R. J. Blohm, R. E. Reynolds, R. E. Trost, J. E. Hines, and J. P. Bladen. 1991. Band reporting rates for mallards with reward bands of different dollar values. Journal of Wildlife Management 55(1):119-126. Noble, R. L., and T. W. Jones. 1993. Managing fisheries with regulations. Pages 383-402 in C. C. Kohler and W. A. Hubert, editors. Inland fisheries management. American Fisheries Society, Bethesda, MD.

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51 Orth, D. J. 1979. Computer simulation model of the population dynamics of largemouth bass in Lake Carl Blackwell, Oklahoma. Transactions of the American Fisheries Society 108:229-240. Pollock, K. H., J. M. Hoenig, W. S. Hearn, and B. Calingaert. 2001. Tag reporting rate estimation: 1. an evaluation of the high-reward tagging method. North American Journal of Fisheries Management 21:521-532. Renfro, D. J., W. F. Porak, and S. Crawford. 1995. Tag retention of Hallprint dart tags and tag-induced mortality in largemouth bass. Proceedings of the Annual Conference of the Southeast Association of Fish and Wildlife Agencies 49:224-230. Ricker, W. E. 1975. Computation and interpretation of biological statistics in fish populations. Bulletin 191 of the Fisheries Research Board of Canada. SAS (Statistical Analysis Systems) 1996. SAS statistics users guide. SAS Institute, Inc. Cary, North Carolina. Seidensticker, E. P. 1994. Lake Nacogdoches, Texas: a case history of largemouth bass overharvest and recovery utilizing harvest regulations. Proceedings of the Annual Conference of the Southeast Association of Fish and Wildlife Agencies 48:453-463. Schramm, H. L. Jr., and D. C. Smith. 1987. Differences in growth rates between sexes of Florida largemouth bass. Proceedings of the Annual Conference of the Southeast Association of Fish and Wildlife Agencies 41:76-84. Tranquilli, J. A., and W. F. Childers. 1982. Growth and survival of largemouth bass tagged with Floy anchor tags. North American Journal of Fisheries Management 2:184-187. U.S. Department of the Interior, Fish and Wildlife Service, and U.S. Department of Commerce, Bureau of the Census. 2002. 2001 National survey of fishing, hunting, and wildlife-associated recreation, Washington, D.C. U.S. Department of the Interior, Fish and Wildlife Service, and U.S. Department of Commerce, Bureau of the Census. 1998. 1996 National survey of fishing, hunting, and wildlife-associated recreation, Washington, D.C. U.S. Department of Labor. 2002. Bureau of Labor Statistics, Division of Consumer Prices and Price Indexes, Washington, D.C. Wilde, G. R. 1997. Largemouth bass fishery responses to length limits. Fisheries 22(6):14-23.

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52 Zagar, A. J. and D. J. Orth. 1986. Evaluation of harvest regulations for largemouth bass populations in reservoirs: a computer simulation model. Pages 218-226 in Hall, G. E. and M. J. Van Den Avyle, editors. Reservoir Fisheries Management Strategies for the 80s. Reservoir Committee, Southern Division American Fisheries Society, Bethesda, MD.

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53 BIOGRAPHICAL SKETCH Kristin Rene Henry was born on October 5, 1977, in Rochester, New York, the daughter of Robert and Jacquieline Henry. She was raised in the small town of Walworth, New York, with her brother Jason. She acquired a love for the ocean during annual family camping-trips to the Atlantic coast, and decided to purse a degree in marine science at Long Island University/Southampton College in the fall of 1995. She graduated with a B.S. in marine biology in May 1999. After graduation she pursued an interest in fisheries biology working with striped bass on the Roanoke River in North Carolina. In June 2000, she began work as a fisheries technician for the University of Florida and began her graduate work in the Department of Fisheries and Aquatic Sciences at the University of Florida in Ja nuary 2001. She will graduate with a Master of Science degree in May 2003. Her future plans are to travel, spend time with her family, and pursue a career in marine fisheries management.


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Title: Evaluation of Largemouth Bass Exploitation and Potential Harvest Restrictions at Rodman Reservoir, Florida
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Material Information

Title: Evaluation of Largemouth Bass Exploitation and Potential Harvest Restrictions at Rodman Reservoir, Florida
Physical Description: Mixed Material
Copyright Date: 2008

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Source Institution: University of Florida
Holding Location: University of Florida
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EVALUATION OF LARGEMOUTH BASS EXPLOITATION AND POTENTIAL
HARVEST RESTRICTIONS AT RODMAN RESERVOIR, FLORIDA
















By

KRISTIN RENE HENRY


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

UNIVERSITY OF FLORIDA


2003




























Copyright 2002

by

Kristin Rene Henry




























To my parents Robert and Jacquieline Henry, thank you for all your love and support.















ACKNOWLEDGMENTS

My gratitude and appreciation go out to Dr. Mike Allen for serving as my advisor,

mentor, and committee chair; Dr. Daniel Canfield Jr., James Estes, Dr. Ramon Littell,

and Dr. Debra Murie for serving as members of my committee; and Robert Hujik and

Eric Nagid for dealing with the publicity associated with the study, processing all of the

tag returns, and providing advice and assistance throughout the study.

I thank the following people who made significant contributions to the field portion

of the study: J.Berg, T. Bonvechio, R. Burs, P. Cooney, T. Curtis, K. Dockendorf, M.

Duncan, S. Gardieff, J. Greenawalt, J. Hale, B. Hujik, G. Kaufman, S. Keller, E. Naged,

S. Naged, W. Porak, M. Randall, J. Rowe, B. Sergent, W. Tate, K. Tugend, P. Wheeler,

and G. Yeargin.

Finally, I thank everyone who provided advice and comments throughout the study;

their help has been greatly appreciated.

Funding for this study was provided by the Florida Fish and Wildlife Conservation

Commission.
















TABLE OF CONTENTS
page

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

LIST OF TABLES ....................................................... .. ......... .............. vii

LIST OF FIGURES .............. .......................... ............ ........... .......... viii

ABSTRACT .............. .......................................... ix

INTRODUCTION .............. ................................... ..............

M E T H O D S .......................................................................... 5

S tu d y S ite ....................................................................... 5
T ag g in g S tu dy ..................................................................... 5
A ge-and-G row th .................................................................................................. ....... 8
Analysis .............. ................... 8
Tagging Study ..................................... .............................. 8
A g e-an d-G row th ....................................................................... 13
R regulation Sim ulations ....................................................................... 15

R E S U L T S ................................................................................1 8

T aging Study .............................................................................................. ........ 18
A ge-and-G row th ..................................... .......................... 22
R regulation Sim ulations ....................................................................... 23

D IS C U S S IO N ....................................................................................................... 3 5

F U R T H E R ST U D Y ................................................................... ................................4 3

APPENDIX

A REW A R D SIG N -1 ............................................................................................... .......46

B T A G -R E TU R N IN V O IC E ....................................................................................... 47

C R E W A R D SIG N -2 ................................................................48

L IST O F R E FE R E N C E S .............................................................................. 49



v









B IO G R A PH IC A L SK E T C H ...................................................................... ..................53















LIST OF TABLES

Table p

1. Estimated catch of 2,638 largemouth bass tagged and released at Rodman Reservoir,
F lo rid a ...................................... ................................ ................ 3 0

2. Tag loss rates for single-tagged (p) and double-tagged (p2) largemouth bass at
R odm an R reservoir ...................... .. ........................... .. ...... .... ........... 32

3. Quarterly catch rates of tagged fish caught from Rodman Reservoir during the
first 3 quarters of 2001 and 2002 .... ...................... ...............33
















LIST OF FIGURES


Figure page

1. Rodman Reservoir located in Putnam and Marion Counties, Florida..........................25

2. Von Bertalanffy growth models fit to mean-length-at-age values for male (triangles)
and female (squares) largemouth bass collected from Rodman Reservoir in
Janu ary 2002 ........................................................................26

3. Weighted catch curve based on number-at-age data for all fish collected during
electrofishing transects conducted at Rodman Reservoir in January 2002............27

4. E stim ated annual harvest of all fi sh ..................................................................... ... 28

5. Estim ated annual catch of all fish ................................................... ..................29















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

EVALUATION OF LARGEMOUTH BASS EXPLOITATION AND POTENTIAL
HARVEST RESTRICTIONS AT RODMAN RESERVOIR, FLORIDA

By

Kristin Rene Henry

May 2003

Chair: Dr. Micheal S. Allen
Major Department: Fisheries and Aquatic Sciences

Rodman Reservoir is considered a premier largemouth bass fishery in Florida, but

the large-fish (> 510-mm TL) potential of the reservoir could potentially be enhanced

with a harvest restriction. I conducted a variable reward tagging study to estimate

exploitation of largemouth bass at Rodman Reservoir. A total of 2,650 largemouth bass

> 345-mm TL were tagged from 2000-2002 using Hallprint dart-style tags. Monetary

rewards for tag returns ranged from $5-$100. Total mortality of largemouth bass was

estimated from a catch curve and gender-specific growth rates were determined from

annuli on sagittal otoliths. An age-structured model was used to simulate the response of

the fishery to various harvest restrictions. Tag returns showed that 42% of the

largemouth bass at Rodman Reservoir were caught in 2001; 11% of the population was

harvested, whereas 31% of the population was caught and released. Total annual

mortality was estimated at 49% and natural mortality at 38%. Length-specific

exploitation rates increased with fish size, indicating a preference among anglers for









harvesting large fish. Simulations showed that harvest of memorable-sized fish was

highest under a 510-mm minimum length limit. Overall total catch (fish > 254-mm TL)

and total catch of memorable-sized fish (> 510-mm TL) under the 510-mm minimum

length limit were second only to a catch and release regulation. Therefore, a 510-mm

minimum length limit would maximize angler catch rates but also allow anglers to

harvest large (> 510-mm TL) fish.















INTRODUCTION

Largemouth bass Micropterus salmoides support some of the most important

freshwater fisheries in the United States. The U.S. Fish and Wildlife Service estimates

that approximately 11.3 million American anglers pursue black bass (U.S. Department of

the Interior 2002). Freshwater fishing expenditures in Florida totaled an estimated $720

million in 1996, with 663,000 anglers targeting black bass. This is more than twice the

number of anglers that target any other freshwater sportfish in Florida (U.S. Department

of the Interior 1998).

Use of harvest restrictions has become an important part of maintaining and

improving largemouth bass fisheries. Harvest restrictions typically include length limits,

slot limits, and bag limits. Objectives of harvest restrictions are to manipulate predator-

prey relationships, increase growth rates of abundant but stunted individuals, increase

population size, increase the number of large fish, and/or increase angler catch rates

(Noble and Jones 1993).

Wilde (1997) compiled data from 49 minimum length-limit evaluations and 42 slot-

limit evaluations for largemouth bass at 88 lakes across the United States. He identified

trends in the response of largemouth bass populations to minimum length and slot limits.

Wilde (1997) found that minimum length limits increased catch rates of largemouth bass,

whereas slot limits (305-381 mm TL) increased the relative abundance of quality and

preferred-size largemouth bass. No evidence indicated that minimum length limits

increased the proportion of large fish or that slot limits increased angler catch rates









(Wilde 1997). A length-limit evaluation at Lake Harris, Florida, found a 40% increase in

angler catch rate two years after implementation (Benton and Douglas 1994). This

increase concurred with the length limit trends described by Wilde (1997).

Managers and research scientists have used computer models to predict the impact

of regulations on a fishery (Orth 1979; Zagar and Orth 1986; Beamesderfer and North

1995; Allen et al. 2002). Zagar and Orth (1986) modeled the effects of minimum length

and slot limits on a hypothetical largemouth bass fishery to identify optimal regulations.

They recommended a 356-mm minimum length limit to managers interested in

maximizing biomass harvested or a 305-406 mm slot limit for creating trophy bass

fisheries (Zagar and Orth 1986).

Models have been used to assess largemouth bass population responses to length

limits on national and regional levels. Beamesderfer and North (1995) characterized

largemouth bass populations within the Untied States by productivity level (i.e., low,

average, or high growth and natural mortality rates) and simulated the effects of length

limits at each productivity level. Beamsderfer and North (1995) found that population

responses to length limits (e.g., changes in yield, harvest, and biomass) were strongly

influenced by the productivity level of the population and that managers' options increase

with population productivity. Allen et al. (2002) assessed the potential benefits of

harvest restrictions based on growth and total mortality of 32 largemouth bass

populations in Florida waters. They indicated that length limits would improve yield and

total catch if growth was at least average and natural mortality was not substantially

higher than exploitation; they also found that high length limits reduced harvest

regardless of growth rate but improved angler catch rates.









Rodman Reservoir is a popular largemouth bass fishery with a reputation for

producing trophy fish. According to the Florida Fish and Wildlife Conservation

Commission (FFWCC) "Big Catch" program, a largemouth bass must be 3.6-kg or 610-

mm TL to qualify for trophy status. During the spring of 2000 two largemouth bass were

caught from the reservoir weighing 7.7-kg and 6.8-kg (Dan Canfield, Florida Lakewatch,

personal communication). The state record is currently held at 7.8-kg (FFWCC); thus

Rodman Reservoir has the ability to produce trophy bass.

The largemouth bass population at Rodman Reservoir, Florida has historically been

managed under statewide regulations. Regulations during standard operating conditions

(5.49-m above mean sea level) restrict angler harvest with a five fish bag limit and 356-

mm length limit, and allow only one fish in the bag limit to exceed 550-mm TL.

Additional regulations have been applied to the reservoir during periods of drawdown.

Regulations for the 2001/2002 drawdown (3.35-m above mean sea level) maintained the

five fish bag limit while increasing the length limit to 610-mm TL. Length limit

exemptions, however, have been granted to tournament anglers by the FFWCC at all

operating levels of the reservoir.

Anglers have expressed a desire for managers to further improve the largemouth

bass fishery at Rodman Reservoir. In response, I evaluated the potential for harvest

restrictions to enhance the largemouth bass fishery at Rodman Reservoir by identifying

regulations that would increase angler catch rates and/or increase the occurrence of large

fish (> 510-mm TL) in the creel. The objectives of this study were to (1) estimate angler

exploitation of largemouth bass using a reward-based tagging study; (2) estimate total

annual mortality using catch curve analysis; (3) estimate age and growth using otoliths;






4


and (4) employ computer models, based on these estimates of exploitation, total annual

mortality, and age and growth, to identify harvest restrictions that would increase overall

total catch (fish > 254-mm TL), total catch of large fish (> 510-mm TL), and harvest of

large fish at Rodman Reservoir.















METHODS

Study Site

Rodman Reservoir is a 3,700-ha eutrophic system located in Putnam and Marion

Counties, Florida. A relict of the Cross Florida Barge Canal project, Rodman Reservoir

encompasses a 26-km flooded section of the Ocklawaha River stretching from the Eureka

dam to the Senator George Kirkpatrick dam. Three distinct areas characterize the

reservoir. Upstream the reservoir consists of floodplain forest and riverine habitat. A

transition zone consisting of flats, stumps, and a submerged river channel follows leading

into the main pool of the reservoir (Canfield et al. 1993). The reservoir has a mean depth

of 2.11-m (Canfield et al. 1993). Six boat launches provide access to the reservoir.

Under normal operating conditions Rodman Reservoir is maintained at 5.49-m

above mean sea level (msl). The reservoir is drawn down at three to five year intervals to

control aquatic macrophytes. During drawdown periods the reservoir is reduced to 3.35-

m above msl, decreasing the flooded area by approximately 2,000 hectares (R. Hujik,

FFWCC, personal communication). The most recent drawdown event began December

1, 2001 and lasted until April 1, 2002. During this time a 610-mm minimum length limit

was placed on the largemouth bass fishery. This temporary regulation was intended to

prevent excessive harvest of largemouth bass during the drawdown.

Tagging Study

I divided the reservoir into four areas (Figure 1) and tagged an approximately equal

number of fish in each area. Area one included water north of the barge canal, west of









the state route 19 bridge, and east of the Kenwood entrance. Area two included all water

south of the barge canal and east of the Kenwood entrance. Area three included water

between the Kenwood entrance and the power lines at Orange Springs and Area four

include all water between the power lines and the entrance to Paynes Landing (Figure 1).

No fish were tagged upstream of Paynes Landing.

Fish were collected for tagging with a boat electrofisher and from angler

tournaments. Largemouth bass were captured using a 4.88-mjon boat outfitted for

electrofishing with a Coffelt VVP-15 electrofisher, as well as a Smith-Root SR-18H

electrofishing boat outfitted with a 9.0 GPP electrofisher. Both systems output DC

current at five to seven amps. All largemouth bass 345-mm TL and greater were

measured to the nearest millimeter total length (TL), tagged, and released into

approximately the same area from which they were captured. Tournament-caught fish >

345-mm TL were measured to the nearest millimeter, tagged, and released into the barge

canal between Areas 1, 2, and 3 (Figure 1). I assumed, based on previous age-and-

growth data for largemouth bass at Rodman Reservoir (Allen et al. 2002), that all tagged

fish 345-355 mm TL would recruit to the fishery (> 356-mm TL) within four months of

tagging.

Largemouth bass were tagged with 103-mm long plastic Hallprint dart tags with a

barb (18-mm long) and orange streamer (85-mm long). The monetary reward value,

return address, and a tag specific identification number were printed on the streamer of

each tag. Tags were injected into the body of the fish below the spiny dorsal fin rays

using a hollow stainless steel needle. When injected the barb of the tag hooked behind a









pterygiophore and the streamer extended in a posterior direction at a 45-degree angle to

the body.

Largemouth bass were tagged during two tagging periods to allow estimates of

exploitation in 2001 and 2002. The length of each tagging period was dictated by the

amount of time it took to tag approximately 1,300 fish. Tagging period one lasted from

November 2000 to March 2001 and tagging period two lasted from December 2001 to

January 2002. Fish were tagged with either one tag (single-tagged) or two tags (double-

tagged) during both tagging periods. Double-tagged fish were later used to estimate tag

loss rates. Single-tagged fish had a monetary reward value of either $5 or $50 and

double-tagged fish had a monetary reward value of $10 (2-$5 reward tags), $55 (1-$5 and

1-$50 reward tag), or $100 (2-$50 reward tags). Double-tagged fish worth $100 were

only released during tagging period-2. The variable-rewards offered for tag returns were

later used to estimate the reporting rate of tags. No tournament fish were double tagged,

due to a desire to minimize the handling time of these fish. Tag returns from double-

tagged fish were considered as a single return.

Press releases to local newspapers and reward signs were used to inform the public

about the study. Reward signs (Appendix 1) were posted at fishing access points around

the reservoir and at local bait and tackle shops. Mailer envelopes with tag-return forms

were available at local bait and tackle shops and were provided to anglers upon request.

Tag-return forms requested the angler name, address, social security number (required to

receive reward), date and location fish was caught, approximate length, fate of the fish

(i.e., harvested or released), and if the fish was caught during a tournament (Appendix 2).









Age-and-Growth

Age and growth of largemouth bass at Rodman Reservoir were estimated using fish

collected with electrofishing in January 2002. All largemouth bass collected during 20-

minute electrofishing transects were measured to the nearest millimeter total length. Five

fish per centimeter group up to 39-cm TL and all fish > 40-cm TL, excluding fish > 5.9-

kg, were collected and returned to the laboratory where weight and gender were

determined, and otoliths were removed.

Sagittal otoliths were removed from sub-sampled fish and read in whole-view

under a dissecting microscope by three independent readers. Otoliths that were 3-years

or older and otoliths with reader discrepancies when examined in whole-view were

sectioned (Hoyer et al. 1985). Two to four 0.50-mm sections were cut from the focus of

each otolith using a South Bay Technology low speed diamond wheel saw (model 650).

Sections from each fish were mounted on a half-frosted slide using Thermo Shandon

synthetic mount. Sectioned otoliths were read under a compound microscope by a

minimum of two independent readers. Sectioned otoliths with reader discrepancies were

re-read by the original readers as well as one additional reader. If the discrepancy

remained, the otolith was discarded. Crawford et al. (1989) found the formation of annuli

to occur as early as April for largemouth bass in Florida lakes, therefore because fish

were collected for age-and-growth in January I assumed a January birth date and assigned

each fish an age one year greater than the number of rings observed on the otolith.

Analysis

Tagging Study

Tag returns were adjusted for tag loss, tagging-related mortality, and non-reporting,

prior to estimating total annual catch and angler exploitation. Tag returns and









electrofishing recaptures of double-tagged fish were used to estimate tag loss. Anglers

that returned single tags from double-tagged fish were contacted by phone to verify that

only one tag was present at the time of capture. The time between tagging and recapture

was recorded for all double-tagged fish. I assumed that tag retention was linearly related

to time-at-large and developed two models, as per Miranda et al. (1997), to estimate the

logistic probability of tag loss (logit(/)) based on the period (P) in which the fish were

tagged:

logit(l) = a + b(time) (1)

where a is the intercept estimate, bl is the parameter estimate, and time is the number of

days between tagging and recapture. Tag returns from double-tagged fish were assigned

a dummy variable of 1 to indicate a single tag loss or 2 to indicate no tag loss. The

dummy variables and associated estimates of time at large (time) for tag returns from

double-tagged fish tagged in each period (P) were then used in Procedure LOGISTIC

(SAS 1996) to calculate estimates of a and bl for each tagging period. Once the

parameter estimates were obtained for equation 1, I estimated the logistic probability of

tag loss (logit(/)) for each tagging period and year based on the average time fish from a

given tagging period (P) were at large in year (y). These logistic probabilities were then

used in the following equation to calculate the probability of a single tag loss (p) for fish

tagged in period P and recaptured during year y (Miranda et al. 1997):

elogit(/)
P ( logit(1)) (2)


I assumed that all tag loss events were independent and subsequently estimated the

probability of a fish losing two tags as the square of the probability of a single tag loss









(p2). Estimates ofp and p2 were then subtracted from 1 to predict tag retention rates for

single-tagged fish (l-p) and double-tagged fish (1-p2). The total number of single-tagged

(Nsingle) and double-tagged (Ndouble) fish from each tagging period and year were then

adjusted based on their respective retention rates.

Tag-related mortality was estimated based on the results of a cage study, which

was conducted within the reservoir. A 2-m x 1-m x 1-m cage with 10-cm plastic bar

mesh was used to hold 3 to 16 fish per cage trial. Six to nine cage trials were conducted

per tagging period with each trial lasting a minimum of 40-hours. All cage trials were

conducted in Area 3 (Figure 1) of the reservoir. At the end of each trial fish were

checked for survival and released. Trials were conducted using fish captured via

electrofishing (trials = 11) as well as those collected at tournaments (trials = 4). The total

number of tagged fish were separated by capture method and tagging period, adjusted for

the appropriate tag-related mortality rate, and recombined.

Reporting rates of high-dollar reward tags in 2001 were estimated based on a

linear-logistic model created by Nichols et al. (1991):

S= e( 0.0045+0.0283(H))/(1 e (-0.0045+0.0283(H))) (3)

where H is the dollar value of a fish tagged with a high-dollar reward (i.e., $50, $55, or

$100) and XH is the reporting rate of tags from high-reward fish. This model was

originally created to estimate the reporting rate of duck bands based on the monetary

reward value of the band. Because the model was created in 1988, the reward values (H)

were converted from 2001 standards to the 1988 monetary equivalents based on the

Consumer Price Index (Nichols et al. 1991). The 1988 monetary equivalents used in

equation 3 were $33.40, $36.71, and $66.80 for $50, $55, and $100 rewards, respectively









(U.S. Department of Labor 2002). Reporting rate estimates calculated from equation 3

were most precise at high-reward values (Nichols et al. 1991). Therefore, I used equation

3 to estimate reporting rates of high-reward fish then calculated the reporting rate of low-

reward tags based on the assumption that all tagged fish had an equal probability of

recapture regardless of reward-value (equations 4 & 5).

I estimated the total number of H reward fish caught (CH) from the reservoir in

2001 using the following equation:


CH = R (4)

where RH is the number of tags returned in 2001 from fish tagged with a high-reward.

Equation 4 was repeated for all values of H. I then estimated the number of low-reward

fish caught (CL) from the reservoir in 2001 using the following ratio:

C C
50 L (5)
=- (5)
T0 TL

where L is the dollar value of a fish tagged with a low-reward (i.e., $5, $10), C50 is the

estimated number of $50-reward fish caught from the reservoir, and T50 and TL are the

original number of fish tagged with a $50-reward and a low-reward (L) respectively,

adjusted for the appropriate rates of tag loss (p, p2) and tagging mortality. Equation 5

was repeated for all values ofL. I then substituted RL (the number of tag returns from

low-reward value fish) and CL into equation 4 to estimate a reporting rate for low-reward

fish (4L) in 2001. This process was repeated for all low-reward values (i.e., $5 and $10).

Reporting rate estimates for all reward values were varied by + 50% to simulate possible

error associated with the reporting rate estimates.








Total annual catch (TAC) and total quarterly catch (TQC) of largemouth bass in

2001 were calculated as follows:

( C20ool0 + C.,2001)
STAC2001 (6)


SL,q,2001S + H,q,2001
q q,2o (zL, TH.,P ) ( L,,,2001 + ( H,,2001)

where 2001 denotes the year in which the fish were caught, P1 denotes the period in

which the fish were tagged (i.e., P1 = period 1), q represents the quarter in which the fish

were caught (i.e., qi = January 1st to March 31st, q2 = April 1st to June 30th, etc.), and i

represents all quarters previous to q within 2001.

Due to time constraints, I was unable to obtain a full year of tag return data for

2002 and therefore unable to estimate reward-specific reporting rates for 2002. However,

assuming that reporting rates did not vary significantly between years, I was able to use

the 2001 reporting rate estimates to calculate an estimate of the total number of

largemouth bass per reward value caught (CH,q,2002, CL,q,2002) from the reservoir in the first

three quarters of 2002 (equation 4). Quarterly estimates of CH and CL were then used to

estimate TQC of largemouth bass in 2002.

q2002Z CL q2002 C Hq,2002
.... (8)
H q)2 L H ) ( CL ,2002 +I CH,,,200)- x
P

X = v(Z TLP, + Z TH P, ) ( CL,2001 + Z CH,2001) (9)

where 2002 denotes the year in which fish were caught, i represents all quarters previous

to q within 2002, and X is a correction term that accounts for the reduced number of

season-1 fish present in the population at the start of 2002 due to natural mortality (v)









(see below) and tag removal in the previous year. Equation 9 assumes that all tags were

removed from fish caught by an angler in 2001, regardless of fate. Angler harvest of

tagged fish during the last month of the fourth quarter of 2001 and the entire first quarter

of 2002 was limited by the temporary 610-mm minimum length limit placed on the

largemouth bass fishery during the 2001/2002 reservoir drawdown.

Total harvest of largemouth bass per reward value (HL, HH) was estimated by

adjusting the number of fish reported by anglers as harvested for non-reporting. Tag

returns from fish with an unknown fate were divided proportionally among the known

fate groups prior to reporting rate adjustments. Estimates of HL and HH were used in

equation 6 in place of CL and CH to estimate total annual exploitation (u) (Ricker 1975) of

largemouth bass in 2001. The total annual exploitation rate was then subtracted from the

total annual catch rate to estimate the total annual catch and release rate for the reservoir.

Age-and-Growth

Data from the timed electrofishing transects was used to estimate total annual

mortality and gender-specific growth rates. I created a gender-specific age length key

from the subsampled largemouth bass collected during January 2002. Age-1 largemouth

bass of unknown gender were randomly assigned a gender based on the assumption that

sexually dimorphic growth rates are not evident in largemouth bass until age-2 (Schramm

and Smith 1987). I used a gender-specific age length key to assign a gender and age to

each individual in the whole sample (all fish captured during timed electrofishing

transects, January 2002). Gender-specific age frequencies were calculated and a catch

curve was fit for each gender. Age-1 fish were not included in the catch curve because

these fish had not fully recruited to the gear (Bayley and Austen 2002). Due to a low

sample size of older fish (< 5 fish per age-class over the age of 6) weighted catch curves








were fit to age-frequency plots. The instantaneous rate of total mortality (Z) was

estimated from the slope of the catch curve for each gender (Ricker 1975). I used the

following equations to estimate total annual mortality (A) and the annual rate of natural

mortality (v) for each gender (Ricker 1975):

A= 1- e- (10)

v =A-u (11)

I used the following equations to estimate mean-length-at-age (MLA) and variance

(02) for each gender (DeVries and Frie 1996):


MLA x (12)


2 ((ZJ)(Zfx2) (fX)2)
2f (13)
( ( ) [ ( -Z ) 1 ] ) ( 1 )

where x is a given centimeter group andf is the number of gender i fish of a given age in

centimeter group x. I used the von Bertalanffy growth model (Ricker 1975) to describe

gender-specific growth rates:

MLA = L(- e-k(age- to) (14)

Parameter estimates (Lo, k, to) were obtained for equation 14 using Procedure

NLIN (SAS 1996) and were based on previously calculated estimates of mean-length-at-

age (equations 12 & 13). The growth models were used to estimate mean total-length-at-

age (TLA) for each gender. Weight-length equations were created for male and female

largemouth bass at Rodman Reservoir based on the subsample of fish collected in 2002

(Ricker 1975):









W=aLb (15)

where W is the weight of the fish, L is the length of the fish, a is the intercept, b is the

shape parameter. Parameters were estimated from the loge transformed model:

log(W)= loga b log(L) (16)

Regulation Simulations

I used the Inland Fisheries Regulation Simulator (IFREGS) model described by

Allen and Miranda (1998) to simulate the response of the fishery to four minimum length

limits; 254-mm TL, 356-mm TL, 457-mm TL, and 510-mm TL, three slot limits; 381-

510-mm TL, 381-559-mm TL, and 381-610-mm TL, a maximum length limit; 457-mm

TL, and a complete catch and release regulation. The model required estimates of

gender-specific total length-at-age, gender and age specific rates of exploitation and

natural mortality, and parameter estimates from gender-specific weight-length equations

to forecast the annual age-structure of the population under a given harvest restriction.

Gender-specific estimates of mean TL-at-age were obtained from the von Bertalanffy

growth models (equation 14). Estimates of TL-at-age were used to describe annual

incremental growth. Within year growth was assumed to be linear. Gender and age

specific exploitation rates were obtained by calculating length specific exploitation rates

for quality (300-379 mm TL), preferred (380-509 mm TL), and memorable (510+ mm

TL) size fish (Anderson and Neumann 1996) and assigning these exploitation rates to

each gender based on mean total-length-at-age (equation 14). Gender and age specific

natural mortality rates were obtained by subtracting the gender and age specific

exploitation rates from total annual mortality (equation 11) and the parameter estimates

for the gender-specific weight-length equations were obtained from equation 15.









Gender and age specific exploitation rates were used to estimate total harvest (fish

> 254-mm TL) and harvest of quality, preferred, and memorable size fish. Gender and

age specific natural mortality estimates were combined with exploitation estimates to

describe total annual mortality and to predict the number of fish in the population each

year. The parameter estimates from the gender-specific weight-length equations were

used to transform fish lengths to fish weights in order to predict the annual biomass of the

population.

The model simulated length limits by protecting fish from harvest if they were

below a minimum length limit or within a slot limit. The model assumed that all fish >

254-mm TL were susceptible to harvest if they were not protected by a regulation. I ran

each simulation for 50-years with 1000 fish recruiting to age-1 (500-males, 500-females).

I used the predicted number of quality, preferred, and memorable size fish harvested as

well as the predicted total number of fish harvested from the 50th simulation year to

compare the effectiveness of each regulation for maximizing harvest. Estimates of

overall total catch (all fish > 254-mm TL) and total catch of quality, preferred, and

memorable size fish were calculated based on the age structure predicted for the 50th

simulation year under a given harvest restriction. Gender and age specific total catch

rates applied to the age structures were obtained by calculating length-specific

exploitation rates for quality, preferred, and memorable size fish and assigning these

catch rates to each gender based on mean TL-at-age. The predicted age structure for the

50th simulation year under each harvest restriction was then multiplied by the appropriate

total catch rates to obtain estimates of overall total catch and total catch of quality,

preferred, and memorable size fish.









In order to account for potential error associated with my reporting rates, all

simulations were repeated using gender-specific exploitation and natural mortality rates

associated with 50% variability in reporting rate. Previous studies that used multiple

methods (e.g., postcard surrogates, phone interviews, creel surveys, or surreptitiously

implanted tags) to estimate reporting rates have shown reporting rate variability to range

from 11% to 52% (Larson et al. 1991; Maceina et al. 1998; Miranda et al. 2002).

Therefore, simulations that used mortality estimates associated with + 50% variation in

reporting rate accounted for potential high variability in my reporting rate estimates.

Simulation results were compared to identify inconsistencies that would result from

incorrectly estimating the reporting rate of tags.















RESULTS

Tagging Study

Tagging-period one ran from November 28, 2000 to March 31, 2001, 50 sampling

trips were made to the reservoir during this time. Forty-four trips were dedicated to

electrofishing and the remaining 6 trips were spent tagging fish collected at tournaments.

A total of 1,368 largemouth bass were tagged during tagging period-1, 1,014 of these fish

were collected by electrofishing, and 354 fish were collected at tournaments. Tagging

period two ran from November 10, 2001 to January 9, 2002, 15 sampling trips were made

to the reservoir during this time. Fourteen of these trips were spent electrofishing and the

remaining trip was spent tagging fish at a tournament. A total of 1,270 largemouth bass

were tagged during period-2, 1,258 of these fish were collected by electrofishing and the

remaining 12 were collected at a tournament. Electrofishing catch rates were higher in

tagging period-2 this was likely due to the reservoir drawdown.

A summary of the number of fish tagged per period and reward value is presented

in Table 1. About half of the fish were tagged with $5 reward tags in both tagging

periods. A low number (n = 6) of $55 reward fish were released during period-1. A total

of 406 and 486 largemouth bass were double-tagged (reward value = $10, $55, $100)

during periods 1 & 2, respectively (Table 1).

Annual tag loss rates for single and double tagged fish are presented in Table 2.

Fish tagged in period-1 were at large an average of 87 days (range = 1 to 337 days)

before recapture in 2001 and 421 days (range = 329 to 528 days) before recapture in









2002. Fish tagged in period-2 were at large and average of 66 days (range = 0 to 250

days) before recapture in 2002 (Table 2). Based on the period tagged and the average

time at large, tag loss ranged from 4% to 26% for single-tagged fish and from 0.2% to

6.6% for double-tagged fish (Table 2). Tag loss was positively related to time at large.

Cage trials were conducted during both tagging periods, 9 trials (6 electrofishing

trials, 3 tournament trials) were conducted in 2001 and 6 in 2002 (5 electrofishing trials,

1 tournament trial). On average 10 fish (range = 3 to 16) were caged per trial and each

trial lasted an average of 50 hours (range = 43 to 79). A total of 145 fish were caged over

the course of the study, all of which survived, resulting in a tag related mortality rate of

0%. Therefore, the original number of fish (N) tagged in each period did not have to be

adjusted for tagging mortality. An estimated 1,314 tagged fish from period-1 remained in

the reservoir after tag loss in 2001 and about 1,246 tagged fish from period-2 remained

after tag loss in 2002. Period-1 fish present in the reservoir in 2002 were adjusted for tag

loss (p = 0.2576, p2 = 0.0663) based on an average of 421 days at large. They were also

adjusted for natural mortality v = 0.38 (described below) and angler removal of tags (n =

546) in 2001. Based on these adjustments I estimated that 382 largemouth bass tagged in

period-1 were present in the reservoir in 2002 (Table 1).

Tag returns were collected from January 1, 2001 to September 30, 2002. Tags

from 260 fish were returned in 2001 and tags from 231 fish were returned in the first

three quarters of 2002. During 2001, the percent return of tags ranged from 16% ($5

reward) to 33% ($55 reward) (Table 1). Estimated reporting rates were positively

correlated with monetary reward values and ranged from 39% ($5 reward) to 87% ($100

reward) (Table 1).









During 2001, 67 tagged fish were reported by anglers as harvested and 180 tagged

fish were reported as released. During the first three quarters of 2002, 24 tagged fish

were reported by anglers as harvested and 203 were reported as released. Thirteen fish

had an unknown fate in 2001 and 4 fish had an unknown fate in 2002. These fish were

divided among the known-fate categories (i.e., kept or released) based on the proportion

of fish in each reward category that were reported as kept or released. Total annual catch,

annual exploitation, and annual catch and release rates for largemouth bass in 2001 were

0.42, 0.11, and 0.31, respectively. Thus, about 26% (i.e., 0.11 / 0.42 = 0.26) of the

largemouth bass caught from the reservoir in 2001 were harvested and about 74% were

released. Tag returns from 2002 showed that the total catch, exploitation, and catch and

release rates for the first three quarters of 2002 were 0.30, 0.03, and 0.27, respectively,

indicating that about 90% of the fish caught in the first three quarters of 2002 were

released.

Length-specific estimates of exploitation, total catch, and natural mortality were

calculated for 2001 based on three length categories; quality (356-379-mm TL), preferred

(380-509-mm TL), and memorable (> 510-mm TL). Annual exploitation rates of quality,

preferred, and memorable fish were 0.08, 0.12, and 0.20, total annual catch rates were

0.38, 0.42, and 0.40, and natural mortality rates were 0.41, 0.37, and 0.29, respectively.

Anglers harvested 22%, 28%, and 50% of all the quality, preferred, and memorable size

fish, respectively, that were caught in 2001. Regulations during the first year of the

tagging study (2001) prevented anglers from harvesting fish < 356-mm TL, because these

fish were protected from harvest (u = 0) estimates of exploitation, total annual catch, and

natural mortality used in the simulation models for fish 254-355-mm TL were therefore









based on the calculated exploitation (u = 0.08), total annual catch (TC = 0.38), and

natural mortality (v = 0.41) rates associated with quality sized fish.

Altering reporting rate estimates by + 50% to account for possible variability

associated with the reporting rate estimates affected the estimates total annual catch,

exploitation, and natural mortality. Increasing reporting rate estimates by 50% resulted in

lower estimates of total annual catch and exploitation and a higher estimate of natural

mortality, reducing reporting rates by 50% had opposite effects. Increasing reporting

rates by 50% resulted in total annual catch rates of 0.26, 0.28, and 0.28, annual

exploitation rates of 0.06, 0.08, and 0.14, and natural mortality rates of 0.43, 0.41, and

0.35 for quality, preferred, and memorable size fish, respectively. Decreasing reporting

rates by 50% resulted in total annual catch rates of 0.76, 0.83, and 0.82, annual

exploitation rates of 0.17, 0.23, and 0.41, and natural mortality rates of 0.32, 0.26, and

0.08 for quality, preferred, and memorable size fish, respectively.

Quarterly tag returns were used to estimate total quarterly catch of largemouth bass

in all quarters of 2001 and in the first three quarters in 2002. TQC rates ranged from 3%

(Quarter-3, 2002) to 22% (Quarter-2, 2001) (Table 3). TQC rates in the first (TQC =

16%) and second (TQC = 22%)) quarters of 2001 were higher than TQC rates in the third

(TQC = 7%)) and fourth (TQC = 3%)) quarters of 2001, indicating a decline in catch

after June 30, 2001. The TQC rate of largemouth bass in the first quarter of 2001 (16%)

was less than the TQC rate in the first quarter of 2002 (20%) (Table 3). Additionally,

TQC rates in the second (22%) and third (7%) quarters of 2001 were higher than TQC

rates in the second (10%) and third (3%) quarter of 2002 (Table 3).









This chapter discusses what a style is, how it is applied, and how it should be used

to create your thesis or dissertation.

Age-and-Growth

Seventeen 20-minute electrofishing transects and one 10-minute electrofishing

transect were conducted from January 7, 2002 to January 9, 2002. A total of 1,239

largemouth bass were collected and measured (whole-sample). Three hundred and

twenty two largemouth bass (sub-sample) collected during sampling efforts, ranging from

80-603 mm TL, were returned to the laboratory to be measured, weighed, and gender and

age determined. Female largemouth bass in the whole sample did not exceed 600-mm

TL, whereas males did not exceed 530-mm TL. Female largemouth bass reached a mean

length of 587 20-mm TL by age-10, whereas male largemouth bass reached a mean

length of 435 6-mm TL by age-10 (Figure 2).

Gender specific values of number-at-age were used for catch curve analysis. Age

classes 7, 9, and 10 were underrepresented (< 5 fish) for both, male and female

largemouth bass. No eight year-old fish were collected. Gender specific rates of total

annual mortality calculated from the slopes of the catch curves were 0.46 and 0.51 for

male and female largemouth bass, respectively. Analysis of covariance showed that there

were no significant differences between the slopes (p = 0.6473) or y-intercepts (p =

0.8200) of the gender-specific catch curves, indicating that total annual mortality was not

significantly different between genders. Thus, gender-specific number-at-age values

were pooled and catch curve analysis was repeated for the pooled sample (Figure 3).

Total annual mortality for all fish was 0.49. Length-specific estimates of natural

mortality mentioned above were calculated based on length-specific exploitation rates

and the pooled estimate of total annual mortality (equation 11). Lengths and weights









pertaining to the sub-sampled fish were used to create the following gender-specific

weight-length equations for male (equation 20) and female (equation 21) largemouth

bass, respectively:

W = (4.42 x 106)L3207 (20)

W = (4.66 x 106)L3196 (21)

Regulation Simulations

Results of the simulations are summarized in Figures 4 and 5. Total annual harvest

of largemouth bass > 254-mm TL and total harvest of quality-sized fish were greatest

under a 254-mm minimum length limit (Figure 4A & 4B). Total harvest of preferred-

sized fish was greatest under a 356-mm minimum length limit (Figure 4C) and total

harvest of memorable-sized fish was greatest under a 510-mm minimum length limit

(Figure 4D). Overall total catch and total catch of preferred and memorable sized fish

were greatest under a catch and release regulation (Figure 5A, 5C, and 5D). The 510-mm

minimum length limit resulted in the second highest overall total catch and total catch of

preferred and memorable sized fish (Figure 5A, 5C, and 5D). The 457-mm minimum

length limit, the 510-mm minimum length limit, and the catch and released regulation all

maximized the total catch of quality-sized fish (Figure 5B).

Assuming anglers would not harvest fish < 254-mm TL, simulating the effects of a

254-mm minimum length limit on the fishery was essentially equivalent to simulating no

length limit. Using this regulation as a benchmark to identify the success of alternate

harvest restrictions revealed that the catch and release regulation, the 510-mm minimum

length limit, and the 457-mm minimum length limit were the top three regulations for

maximizing the overall total catch of largemouth bass as well as the total catch of quality,









preferred, and memorable size fish. The catch and release regulation yielded the highest

increase in total catch, increasing the overall total catch by 32% and increasing the total

catch of quality, preferred, and memorable sized fish by 8%, 54%, and 103%,

respectively compared to no length limit. The 510-mm minimum length limit was the

next most effective regulation for maximizing total catch, increasing the overall total

catch by 18% and increasing total catch of quality, preferred, and memorable sized fish

by 8%, 46%, and 100%, respectively. The 457-mm minimum length limit followed with

a 17% increase in the overall total catch and an 8%, 41%, and 77% percent increase in

the total catch of quality, preferred, and memorable size fish, respectively.

Simulations based on exploitation and natural mortality rates associated with +

50% error in reporting rate showed similar trends with regards to overall total harvest,

total harvest of preferred and memorable sized fish, overall total catch, and total catch of

quality, preferred, and memorable sized fish. However, simulation results associated

with a 50% increase in reporting rate estimates showed that several regulations (254-mm

minimum length limit, 457-mm maximum length limit, 381-510 mm slot limit, 381-559

mm slot, and 381-610 mm slot) would maximize total harvest of quality-sized fish.



















SR 19


Kenwood


Orange 'q~I-


Tournament
Release
Area


i" i hidingg


4 0 4 8 Kilometers
r I


Figure 1. Rodman Reservoir located in Putnam and Marion Counties, Florida. Areas 1-4 represent designated capture and release
areas for the tagging study.











70

60

- 50
E
40

S30


MLAFemales =68.3(1- e0.2102(age+ 0.0035))


MLAMales = 46.0(1- e-0.3525(age 01374))


0 1 2 3 4 5 6 7 8 9 10
Age


Figure 2. Von Bertalanffy growth models fit to mean-length-at-age values for male
(triangles) and female (squares) largemouth bass collected from Rodman
Reservoir in January 2002.














y = -0.68(x) + 7.45
Z = -0.68
A = 0.49


2000 1998


1996
Year Class


1994 1992 1990


Figure 3. Weighted catch curve based on number-at-age data for all fish collected
during electrofishing transects conducted at Rodman Reservoir in January
2002. Total annual mortality of largemouth bass was 49%. A weighted
catch curve was fit to the data because the 1992 to 1995 year-classes were
underrepresented (< 5 fish).


All Fish


1000-


100-


10-


1 -
2002








Total Harvest


254MIN 356MIN 457MIN 510MIN 457MAX


381-510 381-559 381-610
Slot Slot Slot


Quality


254MIN 356MIN 457MIN 510MIN 457MAX 381-510
Slot


381-559 381-610
Slot Slot


Preferred


254MIN 356MIN 457MIN


510MIN 457MAX 381-510 381-559 381-610
Slot Slot Slot


Memorable


254MIN 356MIN 457MIN


H-


510MIN 457MAX 381-510 381-559 381-610
Slot Slot Slot


Regulation


Figure 4. Estimated annual harvest of all fish > 254-mm (A) and quality (300-379-
mm) (B), preferred (380-509-mm) (C), and memorable (> 510-mm) (D)
sized fish based on 50-year simulations run in IFREGS. All estimates are
based on 1,000 fish recruiting to age-1.


60
40
20 -
0


4 '


-n I --


40 -
30 -


20
10
0

C 40


30 -
20 -
10 -
0

15 -


10
5

0


n


Tn


F-I


r


11









Total Catch




F1 n n-


254 MIN 356 MIN 457 MIN 510 MIN 457 381-510 381-559 381-610 Catch &
MAX Slot Slot Slot Release

Quality





254 MIN 356 MIN 457 MIN 510 MIN 457 381-510 381-559 381-610 Catch &
MAX Slot Slot Slot Release

Preferred


254MIN 356MIN 457MIN 510MIN


457 381-510 381-559 381-610 Catch &
MAX Slot Slot Slot Release


Memorable




F n]H F]F


254MIN 356MIN 457MIN 510MIN 457MAX 381-510
Slot


381-559 381-610 Catch &
Slot Slot Release


Regulation


Figure 5. Estimated annual catch of all fish > 254-mm (A) and quality (300-379-mm)
(B), preferred (380-509-mm) (C), and memorable (> 510-mm) (D) sized
fish based on 50-year simulations run in IFREGS. All estimates are based
on 1,000 fish recruiting to age-1.


400 -

350

300 -


250


130

120


140
120
100
80














Table 1. Estimated catch of 2,638 largemouth bass tagged and released at Rodman Reservoir, Florida. The adjusted numbers of
tagged fish were corrected for tag loss (p &p2) and tagging mortality (0%). Period-1 adjusted tagged fish in 2002 were also
corrected for natural mortality and angler removal of tags during 2001. Tag returns were adjusted for non-reporting to obtain
estimated catch.

Tagging Recapture Adjusted Number Percent Reporting Estimated
Period Year Value Tagged Tag Loss Tagged Returned Returned Rate Catch
(P) (y) ($) (N) (p, p2) (T) (R) (%) (W) (C)

1 2001 5 739 0.0557 698 113 16 0.3893 290
1 2001 10* 400 0.0031 399 82 21 0.4944 166
1 2001 50 223 0.0557 210 63 30 0.7192 88
1 2001 55* 6 0.0031 6 2 33 0.7379 3
Total: 1,368 1,313 260 20% 547
Percent: 42%

1 2002 5 739 0.2576 188 23 12 0.3893 59
1 2002 10* 400 0.0663 135 23 17 0.4944 46
1 2002 50 223 0.2576 57 18 32 0.7192 25
1 2002 55* 6 0.0663 2 0 0 0.7379 0
Total: 1,368 382 64 130
Percent: 34%













Table 1. Continued
Tagging Recapture
Period Year


2002
2002
2002
2002
2002


Value
($)


5
10*
50
55*
100*


Total:
Percent:


Adjusted
Tagged Tag Loss Tagged
(N) (p. v2) (T)


686
400
104
50
30
1,270


0.0438
0.0019
0.0438
0.0019
0.0019


Percent Reporting Estimated
Returned Returned Rate Catch


(%)


656
399
99
50
30
1,234


0.3893
0.4944
0.7192
0.7379
0.8650


195
101
32
14
9
351
28%


* Indicates that the fish were tagged with two tags (double-tagged).


\ j \_I j \ j \ j yl j \ j \ j \ j \ j \ j











Table 2. Tag loss rates for single-tagged (p) and double-tagged (p2) largemouth bass
at Rodman Reservoir. Tag loss was estimated based on electrofishing and
angler recaptures of double-tagged fish. Proc LOGISTIC (SAS 1996) was
used to obtain intercept (a) and parameter (p) estimates for tag loss models:
logit(l) = a+b (time).


Tagging Recapture
Period Year


Parameter Average
Intercept Estimate Time


(bl)


(tii)


Tag Loss
Single Tag Double Tag
(p) (p2)


1 2001 -3.2904 0.0053 86.93 0.0557 0.0031
1 2002 -3.2904 0.0053 421.09 0.2576 0.0663
2 2002 -3.7512 0.0101 66.08 0.0438 0.0019












Table 3. Quarterly catch rates of tagged fish caught from Rodman Reservoir during
the first 3 quarters of 2001 and 2002. Adjusted tagged fish were corrected
for tag loss (p & p), tagging mortality (0%), and angler removal of tags (C).
Fish tagged in period-1 and recaptured in 2002 were adjusted for natural


mortality (v = 38%).
catches (C).


Recapture
Year
(y)


2001
2001
2001
2001


Value
($)

5
10
50
55


Returns were adjusted for non-reporting to estimate


Adjusted
Tagged
(T)

698
399
210
6


Number
Returned
(R)


Percent
Returned
(%)


Estimated
Catch
(C)


Percent
Caught
(%)

15
16
20
23


1,313 104


16%


2001
2001
2001
2001


590
336
168
5
1,099


11%


22%


2001
2001
2001
2001


Quarter
(q)


Total
Percent

2
2
2
2
Total
Percent

3
3
3
3
Total
Percent










Table 3. Continued
Recapture
Quarter Year
(a) (v)


Adjusted Number Percent Estimated Percent
Value Tagged Returned Returned Catch Caught
($) (T) (R) (%) (C) (%)


2002
2002
2002
2002
2002


5 844 67
10 534 49
50 156 23
55 52 5
100 30 7
1,616 151



5 672 27
10 435 18
50 124 15
55 45 5
100 22 0
1,298 65



5 603 5
10 399 6
50 103 3
55 38 0
100 22 1
1,165 15


Total
Percent


2002
2002
2002
2002
2002


Total
Percent


20%


2002
2002
2002
2002
2002


3
3
3
3
Total
Percent


10%















DISCUSSION

The optimal harvest restriction for the reservoir should provide the best

combination of overall total catch and total catch of large fish, while catering to angler

preferences. The top three regulations for improving overall total catch and total catch of

memorable-sized fish were (1) the catch and release regulation, (2) the 510-mm

minimum length limit, and (3) the 457-mm minimum length limit. In 2001, anglers

harvested memorable-sized largemouth bass at a much higher rate than smaller fish, thus

eliminating harvest with a catch and release regulation may interfere with preferences of

some angler groups. A catch and release regulation would also prevent tournaments from

taking place at the reservoir because tournament exemptions are prohibited under a catch

and release regulation (FFWCC). During the 2001 fiscal-year, the FFWCC granted

tournament exemptions at Rodman Reservoir to 37 tournament groups which involved

1,018 tournament anglers (W. Chamberlain, FFWCC, unpublished data). Eliminating the

ability to hold future tournaments by instating a catch and release regulation, would

therefore conflict with a substantial number of tournament anglers. Due to the potential

conflicts with angler groups, managers should consider alternatives to the catch and

release regulation.

The 510-mm minimum length limit and the 457-mm minimum length limit were

the next best regulations for maximizing overall total catch and the total catch of

memorable-sized fish. In addition, the 510-mm and 457-mm minimum length limits

were the most effective regulations for maximizing harvest of memorable-sized fish.









Both regulations had a similar effect on the total catch of largemouth bass, however the

total harvest of memorable-sized fish under the 510-mm minimum length limit was 22%

(range: 20% to 50%) higher than total harvest of memorable-sized fish under the 457-mm

minimum length limit. Therefore, the 510-mm minimum length limit would at least be

equivalent to if not better than the 457-mm minimum length limit. I suggest that

managers should consider implementing a 510-mm minimum length limit at Rodman

Reservoir. However, should managers have difficulty instating the 510-mm minimum

length limit because the regulation has not been previously approved for use by the

FFWCC, the 457-mm minimum length limit would serve as a suitable alternative. This

length limit has been previously used by the FFWCC to regulate largemouth bass

fisheries within Florida, and it is the next most effective regulation for maximizing

overall total catch and total catch and harvest of memorable-sized fish.

Estimates of annual exploitation used in the simulation models were based on 2001

tag returns and ranged from 8% (quality fish) to 20% (memorable fish). A review of

mortality rates associated with 30 largemouth bass populations in the United States

showed annual exploitation rates to range from 9-72% (average u = 36%) (Allen et al.

1998). Based on these findings the exploitation rates of largemouth bass at Rodman

Reservoir appear to be low compared to historical data in the United States. Despite the

low rates of exploitation, exploitation rates were positively related to fish length,

indicating a preference among angler to harvest large fish.

The total annual mortality rate used in the simulations was 49%. Allen et al. (1998)

reviewed mortality estimates for 30 largemouth bass populations in the United States and

found total annual mortality rates to range from 24-92% (average A = 64%). Allen et al.









(2002) calculated a 51% average total annual mortality rate for largemouth bass in 45

Florida water bodies. The total annual mortality rate of largemouth bass at Rodman

Reservoir was slightly lower than the national average but similar to the average total

annual mortality of largemouth bass in Florida waters.

Gender-specific mean total-length-at-age estimates used in the simulations

predicted that male largemouth bass would not exceed a mean total length of 443-mm,

thus precluding males from contributing to the memorable-size portion of the population.

Only one male largemouth bass was collected in excess of 510-mm TL during age-and-

growth sampling, therefore males did not contribute greatly to the memorable-size

portion of the population. Regulations that restrict harvest offish < 510-mm TL will

therefore focus the majority of the harvest on the female portion of the population.

Managers should be aware that focusing the majority of harvest on one gender could

eventually skew the sex ratio of the population.

Female largemouth bass at Rodman Reservoir reached memorable size between

ages 6 and 7 and reached an average weight of 2.2-kg by age-11. A previous study by

Allen et al. (2002) examined gender-specific growth rates for 35 largemouth bass

populations in Florida lakes and found that female largemouth bass with average growth

reached memorable size between ages 6 and 7. Therefore, female growth rates at

Rodman Reservoir were about average in comparison to other Florida water bodies.

According to the FFWCC 'Big Catch' program a largemouth bass must be > 610-mm TL

or > 3.6-kg to be considered a trophy catch. Average growth rates at Rodman Reservoir

do not produce trophy fish, thus memorable-sized fish were used as a gauge to measure









each regulation's effectiveness at increasing the number of large fish (> 510-mm TL)

within the reservoir.

Results of the tagging study showed that tag retention rates declined with

increasing time at large. Retention rates ranged from 96% (66 days at large) to 74% (421

days at large), based on the average number of days fish were at large. Renfro et al.

(1995) found 100% tag retention in largemouth bass that were tagged and held in

hatchery ponds for 3-months, and 98% average retention (range: 93% to 100%) for

largemouth bass that were tagged and held in sample ponds for 15-months, using the

same tags used in this study. Renfro et al. (1995) did not find retention rates to decrease

with increasing time at large. Retention rates calculated in this study were lower than

those calculated by Renfro et al. (1995). The individual error associated with fish tagging

was compounded by the high number of individuals (N = 25) that participated in tagging

efforts and may have contributed to the high level of tag loss observed in this study.

Additionally, anglers may have intentionally or inadvertently misreported the presence of

two tags in follow-up phone interviews. Conversations with anglers revealed a common

belief that both tags should not be removed from double-tagged fish. Some anglers

believed that it was wrong to remove both tags, while others believed they were

contributing to the success of the study by not removing all tags. In either case,

misreporting a tag loss from a double-tagged fish would have inflated my estimate of tag

loss. In response to this apparent confusion among anglers, signs were posted at boat

ramps in January 2002, indicating that all tags should be removed from double-tagged

fish (Appendix 3). Tag retention rates may have been more comparable to those found









by Renfro et al. (1995) had the angling community clearly understood how to treat

double-tagged fish.

Cage trials conducted during the fall and winter showed a 100% survival rate for

tagged fish. This survival rate was comparable to the survival rates calculated in

previous tagging studies (Tranquilli and Childers 1982; Renfro et al. 1995). Renfro et al.

(1995) showed that over the course of a three-month pond study mortality rates of fish

tagged with Halprint dart-style tags did not differ significantly from mortality rates of

untagged fish. Tranquilli and Childers (1982) also showed 100% survival rate for tagged

fish in a 191-day pond experiment.

Tag returns may have suffered from a lack of independence. Pollock et al. (2001)

suggested that anglers may have a tendency to collect low-reward tags until they gather

enough tags to make them worth mailing. Anglers participating in this study commonly

returned several tags at once indicating a possible lack of independence. The tag return

envelopes used in this study may have also contributed to the lack of independence in tag

returns. Tag return envelopes were not postage-paid therefore the cost and effort

associated with mailing a single tag may have outweighed the reward, possibly leading

anglers to accumulate tags until they had collected enough reward money to justify

mailing in the tags. This possible lack of independence in tag returns may have inflated

my reporting rate estimates.

The exploitation rate of largemouth bass calculated for the first three quarters of

2002 was low (u2002 = 3%) in comparison to the 2001 annual exploitation rate (u2001 =

11%). Although the 2002 exploitation rate will increase as tags are returned from fish

caught in the fourth quarter of 2002, I do not expect the exploitation rate to increase









dramatically nor do I expect it to match or exceed the 2001 annual exploitation rate. The

low exploitation rate in 2002 was probably due to (1) the 610-mm minimum length limit

implemented during the 2001-2002 reservoir drawdown and (2) a possible decline in the

return rate of tags from 2001 to 2002. The temporary 610-mm minimum length limit

placed on the largemouth bass fishery during the drawdown period coincided with the

first quarter of 2002 and protected the majority of the fish caught during that quarter from

harvest. Because 66% of all the fish caught in the first three quarters of 2002 were

caught during the first quarter of the year, the temporary length limit contributed to the

lower exploitation rate in 2002. In addition, using 2001 reporting rate estimates to

estimate total catch in 2002 may not have been appropriate since reporting rates have

been shown to decline from the first year of the study to subsequent years (Dequine and

Hall 1949; Moody 1960). If reporting rates declined from the first to second year of my

study, the use of first year reporting rates would result in underestimates of exploitation

and total catch in 2002. Reward-specific reporting rates were not calculated for 2002

because a complete year of tag return data was not available. Although 2002 reporting

rates were not available, comparing the percent return of tags in the second (11%) and

third (3%) quarters of 2001 to the second (5%) and third (1%) quarters of 2002 revealed a

decline in the return rate of tags (Table 3). However, the percent return of tags in the first

quarter of the year increased from 2001 (8%) to 2002 (9%) (Table 3). This increase may

be an indication that tag return rates did not decline with increasing study length.

Nevertheless, it is more likely that a decline in reporting rates occurred and was masked

by an increase in angler catch rates associate with the reservoir drawdown. Therefore,









angler catch rates calculated for the first three quarters of 2002 were probably

underestimated, leading to an underestimate of exploitation and total catch for 2002.

Harvest restrictions are often more effective at altering the age structure of

populations that have additive mortality rates as opposed to compensatory (Allen et al.

1998). Changing exploitation rates in populations with additive mortality has a direct

effect on total annual mortality. However, changing exploitation rates in populations

with compensatory mortality may not effectively reduce total annual mortality. Growth

and natural mortality of a population may also dictate the effectiveness of a regulation.

Beamesderfer and North (1995) found that angler catch rates and the occurrence of large

fish were likely to increase when harvest restrictions were applied to average (average

growth, average v) or productive (fast growth, low v) populations. Conversely, they

found that limiting exploitation of unproductive populations (slow growth, high v) may

not be beneficial because many fish would die before they reached quality size.

Compared to the populations studied by Beamesderfer and North (1995), growth rates

and natural mortality of largemouth bass at Rodman Reservoir were average. Based on

these findings and the assumption that mortality rates of largemouth bass were additive,

harvest restrictions should serve as an effective means for manipulating the age structure

of the largemouth bass population at Rodman Reservoir.

Miranda et al. (2002) questioned the effectiveness of tagging studies as a means for

accurately assessing exploitation rates. They reported that the variability associated with

estimating reporting rates is so large that it precludes a manager's ability to accurately

assess exploitation, thus Miranda et al. (2002) recommended that managers seek an

alternate means for estimating exploitation. Because my exploitation rates were derived









from a tagging study, I introduced high error into my reporting rate estimates and used

the associated exploitation and natural mortality rates in simulation models to verify that

trends in the simulation results would remain constant regardless of the possible

variability associated with my reporting rate estimates. Simulations using exploitation

and natural mortality rates associated with + 50% variability in reporting rate showed that

trends in total catch remained constant. Trends in total harvest were moderately affected

by the extreme variation in reporting rates. Overall, variability in exploitation due to

reporting rate error did not significantly impact the relative value of each harvest

restriction.

The purpose of the simulation model was to identify trends in the population's

response to various harvest restrictions. Simulation models have error associated with

their estimates just as field data have associated error (Johnson 1995). Therefore, error

associated with specific predictions of the simulation model my recommendation to

implement a 510-mm minimum length limit at Rodman Reservoir was based primarily on

the trends reveled by the simulations, not the specific values.















FURTHER STUDY

Several factors could interfere with the success of the proposed 510-mm minimum

length limit. These factors include (1) a potential for reduced growth due to the proposed

high minimum length limit, (2) a potential for increased fish removal during tournaments

due to the re-opening of Buckman Lock, and (3) the potential elimination of the reservoir

due an ongoing debate to remove of the Senator George Kirkpatrick Dam.

The proposed high minimum length limit could potentially reduce the growth rates

of largemouth bass at Rodman Reservoir, thus interfering with the success of the

proposed regulation. Seidensticker (1994) found evidence that slow growth of

largemouth bass began 5-years after a 406-mm minimum length limit was implemented

at a Texas reservoir. I suggest conducting semi-annual age-and-growth surveys at the

reservoir to assess the potential effects of the regulation on fish growth rates. Age-and-

growth assessments would allow managers to identify potential problems as well as track

the success of the regulation as a means for altering the age structure of the population.

According to Allen and Pine (2000) the probability of detecting differences in the age

structure of a population due to an altered harvest restriction was higher under 5-year

evaluations than 3-year evaluations. Wilde (1997) concluded that data should be collected

for a minimum of three years following the implementation of a regulation in order to

detect differences. In either case, duration of evaluation was the key to determining the

effects of a regulation on a population. Based on these finding, I suggest monitoring age-

and-growth of the population periodically for 5-7 years.









The re-opening of Buckman Lock could lead to an increase in the number of

largemouth bass removed from the reservoir due to tournaments and potentially lead to

an increase in total annual mortality. Buckman Lock connects Rodman Reservoir to the

St. Johns River allowing boater access between the two water bodies. The lock is

commonly used by tournament anglers participating in fishing tournaments held outside

of the reservoir. Tournament anglers that lock through to fish the reservoir remove

largemouth bass from the reservoir when they return to the St. Johns River for weigh-ins.

Tournament anglers participating in tournaments outside of the reservoir do not release

fish back into the reservoir, thus tournament anglers could potentially contribute to the

total annual mortality of largemouth bass at Rodman Reservoir. Buckman Lock was

closed for the duration of this study except for a brief period in December of 2001 when

the lock was opened to allow anglers participating in the Citgo Bassmasters Eastern Open

to fish the reservoir. Buckman lock re-opened for regular operation in October of 2002.

Due to the re-opening of the lock, I recommend that managers assess effects of outside

tournament anglers on the abundance of largemouth bass at Rodman Reservoir. If

tournaments remove a significant number of fish, I suggest re-evaluating the harvest

restriction to ensure that the 510-mm minimum length limit is still the optimal regulation

for the reservoir.

Finally, the potential elimination of the reservoir due to an ongoing debate to

remove the Senator George Kirkpatrick Dam and restore the free flowing Ocklawaha

River could completely negate the findings of this study. The US Forest Service has

voiced its intention to initiate action by 2006 to restore the federal land which is currently

submerged beneath the reservoir and abuts the Senator George Kirkpatrick Dam. The









intentions of the US Forest Service would effectively result in the removal of the

reservoir. However, in response to the US Forest Service's intentions, the 'Save Rodman

Reservoir' advocacy group has voiced their plan to file suit against the US Forest

Service, should the US Forest Service take action to remove the dam. Managers should

consider the potential for dam removal when deciding whether to implement a new

harvest restriction. As previously stated, the effects of the regulation may not be visible

for five or more years, thus the removal of the dam could prevent the regulation from

ever taking full effect and if the dam was removed, a re-assessment of the fishery would

need to take place before a new optimal harvest restriction could be chosen. Managers

should take caution and consider all of these potential problems prior to implementing a

new harvest restriction.














APPENDIX A
REWARD SIGN-1


Reward sign posted at fishing access points around Rodman Reservoir and at local tackle
shops.

REWARD

$5 AND $50

Fishery biologists have tagged Largemouth bass in the Rodman Reservoir.
To receive a reward of $5 or $50, you must cut the tag from the fish and
mail the tag and the following information to the address listed below.


Send the following information with each tag:


NAME
ADDRESS
PHONE NUMBER
SOCIAL SECURITY NUMBER*
SIGNATURE


DATE CAUGHT
APPROXIMATE CATCH LOCATION
APPROXIMATE FISH LENGTH
COMMENTS


*Needed to receive reward.

Address information is also provided on the tag, and tag mailers are
provided at local tackle shops for your convenience.
S11 -. 1150 $5FReward I


Please mail tag and information to:
Florida Fish and Wildlife
Conservation Commission
7922 NW 71st St. Gainesville, FL 32653
(352) 392-9617 ext. 240














APPENDIX B
TAG-RETURN INVOICE

Tag- return invoice distributed to all anglers that returned largemouth bass tags.

Please mail tag and information to:
Florida Fish and Wildlife
Conservation Commission
7922 NW 71st St. Gainesville, FL 32653
(352) 392-9617 ext. 240
INVOICE

To: Florida Fish and Wildlife Conservation Commission
7922 NW 71st St.
Gainesville, FL 32653

TO BE FILLED OUT BY ANGLER

From: (Please Print)
Name:
Social Security Number: (Needed for reward)
Address:


Phone Number:( ) -
Approximate Fish Length (inches):
Date Caught:
Approximate Catch Location:
Was Fish Kept or Released
Comments:


Tournament : Yes/No (Circle)
Tournament Name:
Weigh-in Location:












APPENDIX C
REWARD SIGN-2
Informational sign posted at fishing access points around Rodman Reservoir beginning
January 2002. The sign was intended to alleviate confusion among anglers regarding the
number of tags that should be removed from double-tagged fish.


LARGEMOUTH BASS
TAGS

Please Cut All Orange Tags from Fish Regardless of
Whether the Fish is Kept or Released.

REWARDS: $5,$10,$50,$55,$100

Please mail Tags to:

Florida Fish and Wildlife Conservation Commission
7922 NW 71st Street. Gainesville, FL 32653
(352) 392-9617 ext. 240















LIST OF REFERENCES


Allen, M. S., and L. E. Miranda. 1998. An age-structured model for erratic crappie
fisheries. Ecological Modeling 107:289-303.

Allen, M. S., L. E. Miranda, and R. E. Brock. 1998. Implications of compensatory and
additive mortality to the management of selected sportfish populations. Lakes &
Reservoirs: Research and Management 3:67-79.

Allen, M. S., and W. E. Pine III. 2000. Detecting fish population responses to a
minimum length limit: effects of variable recruitment and duration of evaluation.
North American Journal of Fisheries Management 20:672-682.

Allen, M. S., W. Sheaffer, W. F. Porak, and S. Crawford. 2002. Growth and mortality of
largemouth bass in Florida waters: implications for use of length limits.
International Black Bass Symposium.

Anderson, R. O., and R. M. Neumann. 1996. Length, weight, and associated structural
indices. Pages 447-482 in B. R. Murphy and D.W. Willis, editors. Fisheries
techniques, 2nd edition. American Fisheries Society, Bethesda, Maryland.

Bayley, P. B., and D. J. Austen. 2002. Capture efficiency of a boat electrofisher.
Transactions of the American Fisheries Society 131:435-451.

Beamesderfer, R. C. P., and J. A. North. 1995. Growth, natural mortality, and predicted
response to fishing for largemouth bass and smallmouth bass populations in North
America. North American Journal of Fisheries Management 15:688-704.

Benton, J., and D. Douglas. 1994. Ocklawaha chain of lakes largemouth bass population
studies. Pages 29-54 in Upper Ocklawaha River completion reports: 1991 to
1994. Florida game and freshwater fish commission fisheries research laboratory,
Eustis, FL.

Canfield, D. E. Jr., E. J. Schulz, and M. V. Hoyer. 1993. "To be or not to be"--The
Rodman Reservoir controversy. Final report, Department of Fisheries and
Aquaculture, Center for Aquatic Plants. University of Florida, Gainesville.

Crawford, S., W. S. Coleman, and W. F. Porak. 1989. Time of annulus formation in
otoliths of Florida largemouth bass. North American Journal of Fisheries
Management 9:231-233.









Dequine, J. F., and C. E. Hall, Jr. 1949. Results of some tagging studies of the Florida
largemouth bass Micropterus salmoidesfloridanus (LeSueur). Transactions of
the American Fisheries Society 79:155-166.

DeVries, D. R., and R. V. Frie. 1996. Determination of age and growth. Pages 483-512
in B. R. Murphy and D.W. Willis, editors. Fisheries techniques, 2nd edition.
American Fisheries Society, Bethesda, Maryland.

Hoyer, M. V., J. V. Shireman, and M. J. Maceina. 1985. Use of otoliths to determine
age and growth of largemouth bass in Florida. Transactions of the American
Fisheries Society 114:307-309.

Johnson, B. L. 1995. Applying computer simulation models as learning tools in fisheries
management. North American Journal of Fisheries Management 15:736-747.

Larson, S. C., B. Saul, and S. Schleiger. 1991. Exploitation and survival of black
crappies in three Georgia reservoirs. North American Journal of Fisheries
Management 11:604-613.

Maceina, M. J., P.W. Bettolli, S. D. Finely, and V. J. DiCenzo. 1998. Analyses of the
sauger fishery with simulated effects of a minimum size limit in the Tennessee
River of Alabama. North American Journal of Fisheries Management 18:66-75.

Miranda, L. E., R. E. Brock, and B. S. Dorr. 1997. Growth, fishing, and natural
mortality of crappies in Mississippi. Pages 56-70 in Miranda, L. E., M. S. Allen,
R. E. Brock, K. M. Cash, B. S. Dorr, L. C. Issak, and M. S. Schorr. Evaluation of
regulations restrictive of crappie harvest. Mississippi Cooperative Fish and
Wildlife Research Unit. Mississippi State University, Starkville.

Miranda, L. E., R. E. Brock, and B. S. Dorr. 2002. Uncertainty of exploitation estimates
made from tag returns. North American Journal of Fisheries Management
22:1358-1363

Moody, H. L. 1960. Recaptures of adult largemouth bass from the St. Johns River,
Florida. Transactions of the American Fisheries Society 89(3):295-300.

Nichols, J. D., R. J. Blohm, R. E. Reynolds, R. E. Trost, J. E. Hines, and J. P. Bladen.
1991. Band reporting rates for mallards with reward bands of different dollar
values. Journal of Wildlife Management 55(1): 119-126.

Noble, R. L., and T. W. Jones. 1993. Managing fisheries with regulations. Pages 383-
402 in C. C. Kohler and W. A. Hubert, editors. Inland fisheries management.
American Fisheries Society, Bethesda, MD.









Orth, D. J. 1979. Computer simulation model of the population dynamics of largemouth
bass in Lake Carl Blackwell, Oklahoma. Transactions of the American Fisheries
Society 108:229-240.

Pollock, K. H., J. M. Hoenig, W. S. Hearn, and B. Calingaert. 2001. Tag reporting rate
estimation: 1. an evaluation of the high-reward tagging method. North American
Journal of Fisheries Management 21:521-532.

Renfro, D. J., W. F. Porak, and S. Crawford. 1995. Tag retention of Hallprint dart tags
and tag-induced mortality in largemouth bass. Proceedings of the Annual
Conference of the Southeast Association of Fish and Wildlife Agencies 49:224-
230.

Ricker, W. E. 1975. Computation and interpretation of biological statistics in fish
populations. Bulletin 191 of the Fisheries Research Board of Canada.

SAS (Statistical Analysis Systems) 1996. SAS statistics user's guide. SAS Institute,
Inc. Cary, North Carolina.

Seidensticker, E. P. 1994. Lake Nacogdoches, Texas: a case history of largemouth bass
overharvest and recovery utilizing harvest regulations. Proceedings of the Annual
Conference of the Southeast Association of Fish and Wildlife Agencies 48:453-
463.

Schramm, H. L. Jr., and D. C. Smith. 1987. Differences in growth rates between sexes
of Florida largemouth bass. Proceedings of the Annual Conference of the
Southeast Association of Fish and Wildlife Agencies 41:76-84.

Tranquilli, J. A., and W. F. Childers. 1982. Growth and survival of largemouth bass
tagged with Floy anchor tags. North American Journal of Fisheries Management
2:184-187.

U.S. Department of the Interior, Fish and Wildlife Service, and U.S. Department of
Commerce, Bureau of the Census. 2002. 2001 National survey of fishing,
hunting, and wildlife-associated recreation, Washington, D.C.

U.S. Department of the Interior, Fish and Wildlife Service, and U.S. Department of
Commerce, Bureau of the Census. 1998. 1996 National survey of fishing,
hunting, and wildlife-associated recreation, Washington, D.C.

U.S. Department of Labor. 2002. Bureau of Labor Statistics, Division of Consumer
Prices and Price Indexes, Washington, D.C.

Wilde, G. R. 1997. Largemouth bass fishery responses to length limits. Fisheries
22(6):14-23.






52


Zagar, A. J. and D. J. Orth. 1986. Evaluation of harvest regulations for largemouth bass
populations in reservoirs: a computer simulation model. Pages 218-226 in Hall,
G. E. and M. J. Van Den Avyle, editors. Reservoir Fisheries Management
Strategies for the 80's. Reservoir Committee, Southern Division American
Fisheries Society, Bethesda, MD.















BIOGRAPHICAL SKETCH

Kristin Rene Henry was born on October 5, 1977, in Rochester, New York, the

daughter of Robert and Jacquieline Henry. She was raised in the small town of

Walworth, New York, with her brother Jason. She acquired a love for the ocean during

annual family camping-trips to the Atlantic coast, and decided to purse a degree in

marine science at Long Island University/Southampton College in the fall of 1995. She

graduated with a B.S. in marine biology in May 1999. After graduation she pursued an

interest in fisheries biology working with striped bass on the Roanoke River in North

Carolina. In June 2000, she began work as a fisheries technician for the University of

Florida and began her graduate work in the Department of Fisheries and Aquatic

Sciences at the University of Florida in January 2001. She will graduate with a Master of

Science degree in May 2003. Her future plans are to travel, spend time with her family,

and pursue a career in marine fisheries management.