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Objective: To evaluate the vulnerability of Bull Trout Salvelinus confluentus to potential climate changes across its range in Oregon, we compiled disparate expert knowledge of the distribution of spawning and rearing and combined these probabilistic statements as data along with documented records of breeding and rearing in a joint occupancy model. Methods: The joint expert knowledge–occupancy model, which was based on discrete patches of cold water (≤13°C) suitable for spawning and rearing, permitted the association of true occupancy with climate and other explanatory variables while accounting for variation in detection probability. We then applied estimated relationships of patch occupancy with explanatory variables to projected coldwater patch configurations in the years 2040 and 2080. Result: Projections of the kilometers of occupied coldwater patch in future decades suggest precipitous declines if current relationships of occupancy with environmental variables are maintained. Impacts of climate changes in future decades manifest directly through the outright loss of coldwater patches and increases in winter high flows but also indirectly by increased isolation. Conclusion: Combining probabilistic statements of species distributions from knowledgeable experts with sparse occupancy data may be a robust and timely alternative when large numbers of repeated occupancy surveys are infeasible. Impact statementThis study provides a novel approach for developing species distribution models using expert knowledge. This approach may be valuable for applications to species that are difficult to otherwise study or survey. [ABSTRACT FROM AUTHOR]

Understanding trends in abundance is important to fisheries conservation, but techniques for estimating streamwide abundance of cryptic fishes with strong habitat–abundance relationships are not well established and need further development. We developed techniques for addressing this need using the Harlequin Darter Etheostoma histrio, a small, cryptic freshwater fish associated with submerged wood in streams. Our objectives were to (1) determine how Harlequin Darter abundance and the amount of submerged wood were related at sampled sites and (2) use this relationship to estimate Harlequin Darter abundance at unsampled sites and extrapolate Harlequin Darter abundance estimates and associated uncertainty streamwide. We conducted a mark–recapture study to estimate abundance of Harlequin Darters in 25‐m stream reaches at 24 sites in Big Escambia Creek (BEC) and 18 sites in Pine Barren Creek (PBC) (Escambia River tributaries in northwestern Florida). The number of wood pieces (submerged wood ≥1.5 m long and ≥0.25 m in circumference) in both creeks was counted and mapped using side‐scan sonar and a geographic information system. Harlequin Darter and wood data were used in a Bayesian multinomial mixture model to estimate site abundance of Harlequin Darters, to determine the relationship between wood and Harlequin Darter abundance, and to extrapolate Harlequin Darter abundance streamwide. We found a positive relationship between wood and Harlequin Darter abundance in both creeks, and there were more wood pieces in PBC than in BEC. Streamwide abundance of Harlequin Darters was greater in PBC than in BEC. The extrapolated streamwide abundance estimates were 9,369 Harlequin Darters (95% credible interval = 6,668–13,402) in PBC and 7,439 Harlequin Darters (95% credible interval = 4,493–11,226) in BEC. Our methods effectively estimated abundance of a small, cryptic fish that uses complex wood habitat. In addition, our findings may assist in the conservation of the Harlequin Darter. [ABSTRACT FROM AUTHOR]

Angling for trophy Largemouth Bass Micropterus salmoides and Florida Bass M. salmoides floridanus supports popular fisheries, particularly in the southern United States, where conditions are favorable for growing large fish. Traditional standardized sampling gears, such as electrofishing and creel surveys, often prove ineffective at obtaining sample sizes that are adequate for assessing the quality and temporal trends in trophy fisheries. In this study, we assessed the trophy Florida Bass population in the newly impounded Calling Panther Lake (163 ha), Mississippi, by using a nontraditional, specialized angling technique, and we compared the results with data collected by the more traditional techniques of creel surveys and electrofishing. The specialized angling technique utilized a select few highly skilled and devoted anglers that targeted only the largest bass in the population. The specialized angling technique collected nearly 8 and 24 times more trophy Florida Bass (≥3.6 kg or ≥56 cm TL) than creel surveys and electrofishing, respectively. As a result, this was the only method that reliably collected enough trophy‐sized fish to estimate the population size in Calling Panther Lake. Mark–recapture data were used to estimate an abundance of 150 trophy Florida Bass (95% confidence interval [CI] = 118–206) in 2011 (density = 0.92 fish/ha; 95% CI = 0.73–1.26). The use of data collected by specialized anglers provided vital information for the trophy segment of this bass population, which is often difficult for fisheries managers to obtain with traditional techniques. [ABSTRACT FROM AUTHOR]

Fish stocking and harvest regulations are frequently used to maintain or enhance freshwater recreational fisheries and contribute to fish conservation. However, their relative effectiveness has rarely been systematically evaluated using quantitative models that account for key size‐ and density‐dependent ecological processes and adaptive responses of anglers. We present an integrated model of freshwater recreational fisheries where the population dynamics of two model species affect the effort dynamics of recreational anglers. With this model, we examined how stocking various fish densities and sizes (fry, fingerlings, and adults) performed relative to minimum‐length limits using a variety of biological, social, and economic performance measures, while evaluating trade‐offs. Four key findings are highlighted. First, stocking often augmented the exploited fish population, but size‐ and density‐dependent bottlenecks limited the number of fry and fingerlings surviving to a catchable size in self‐sustaining populations. The greatest enhancement of the catchable fish population occurred when large fish that escaped early bottlenecks were stocked, but this came at the cost of wild‐stock replacement, thereby demonstrating a fundamental trade‐off between fisheries benefits and conservation. Second, the relative performance of stocking naturally reproducing populations was largely independent of habitat quality and was generally low. Third, stocking was only economically advisable when natural reproduction was impaired or absent, stocking rates were low, and enough anglers benefitted from stocking to offset the associated costs. Fourth, in self‐sustaining fish populations, minimum‐length limits generally outperformed stocking when judged against a range of biological, social and economic objectives. By contrast, stocking in culture‐based fisheries often generated substantial benefits. Collectively, our study demonstrates that size‐ and density‐dependent processes, and broadly the degree of natural recruitment, drive the biological, social, and economic outcomes of popular management actions in recreational fisheries. To evaluate these outcomes and the resulting trade‐offs, integrated fisheries‐management models that explicitly consider the feedbacks among ecological and social processes are needed. [ABSTRACT FROM AUTHOR]

Abstract: Angling for adult black bass Micropterus spp. as they defend nests containing eggs or fry (i.e., bed‐fishing) has drawn concerns from fishery managers and anglers due to negative impacts on reproductive success. Research efforts, however, have failed to consider bed‐fishing scenarios other than male‐directed targeting, which may inaccurately reflect angler behaviors. To gain insights into the behaviors, motivations, and attitudes associated with bed‐fishing across a large extent of the global distribution of black bass, we surveyed tournament anglers from the southeastern United States and South Africa (where black bass were introduced in 1928). Responses from 440 black bass tournament anglers indicated that during the reproductive season nearly half of all anglers spent 50% or more of their time bed‐fishing and that larger, female fish were preferential targets. Overall, the responses from U.S. and South African anglers were very similar, but significant attitudinal differences were associated with the perceived impacts of bed‐fishing on adult reproduction and juvenile production. Our results suggest that there are commonalities among the preferences and behavior of anglers from disparate geographic regions, and we highlight the need for future research on the impacts of size‐ and sex‐selective bed‐fishing of basses. [ABSTRACT FROM AUTHOR]

Black bassesMicropterusspp. are the focus of extensive management efforts throughout North America, where they support a multibillion-dollar recreational sport fishery. Harvest rates in many bass fisheries have declined in recent decades, yet a growing number of studies have proposed that catch-and-release angling practices, such as bed-fishing in which anglers intentionally target bass while the fish are defending their nests, can decrease individual reproductive success. In response, management agencies have restricted fishing during the spawning period in some regions. We evaluated the impacts of catch-and-release bed-fishing on Florida BassM. salmoides floridanusnest success, reproductive success, production of fall recruits, and the number of parents that contributed to reproduction. Eighteen replicate populations simulating natural Florida lakes were established, and ponds were assigned either a bed-fishing (n= 10) or a control treatment (n= 8). Snorkel surveys were conducted throughout the spawning period to track nest formation and nesting success rates, and 10 months after establishment all ponds were drained, recruits counted, and fin clips collected for genetic parentage analysis. A series of candidate generalized linear mixed models were compared using Akaike’s information criterion and likelihood ratio tests to assess the relative importance of fishing treatment and year, along with other relevant variables in predicting nest success, recruitment, and reproductive success. We observed significant reductions in nest success rates (z= −2.13,P= 0.03) but not recruitment levels (z= −1.31,P= 0.19), in populations that were bed fished relative to control ponds. Capture history poorly predicted individual reproductive success and the number of adults that contributed to fall recruitment did not differ by treatment (χ2= 0.06,P= 0.81). Results from this study indicated that bed-fishing practices may have some impacts on individual nest success but did not influence recruitment or overall reproductive success of Florida Bass at the population level. Received October 5, 2016; accepted February 28, 2017 Published online July 5, 2017 [ABSTRACT FROM AUTHOR]

Angling nesting Florida BassMicropterus salmoides floridanusmay influence the survival of the brood and could negatively affect bass populations. Our objectives were to estimate daily nest survival for Florida Bass and to examine factors that influence nest survival to the swim-up fry stage. Snorkelers examined a total of 259 nests in a small, mesotrophic lake in north-central Florida from 2010 to 2012. We compared nest survival rates with accumulated degree-days, largest temperature drop following nest discovery, nest score, presence of a guarding male bass, and size of the guarding male. The most important factor in determining nest survival was the presence of a male bass. However, guarding male fish were only observed on 66% of active nests despite multiple visits to each nest, indicating a lower tendency to remain with the brood than has been reported in otherMicropterusspecies. Florida Bass have displayed lower nest guarding behaviors in other studies; a prolonged spawning season and the presence of top predators in southern bass populations may influence decreased nest fidelity and nest guarding behavior. Individual nesting attempts may be less important for successful Florida Bass recruitment. Received September 28, 2016; accepted February 28, 2017 Published online May 12, 2017 [ABSTRACT FROM AUTHOR]

Black bassMicropterusspp. support popular freshwater sport fisheries in North America. Bass anglers commonly adopt catch and release as a conservation practice, and frequently over 75% of angled black bass are released back into the water. If fish survive the angling event, the practice of catch and release as an alternative to harvest reduces direct mortality, but it has the potential to affect the postrelease feeding behavior and survival of the fish. The act of lifting black bass for handling, hook removal, and photograph opportunities may cause stress and injury, and the degree of injury sustained could be influenced by fish size. Holding fish in a tilted grip by the jaw has raised concern among anglers about potential damage to jaw musculature and tendons, as they may not support the fish’s body weight out of water, particularly for trophy bass. We conducted an experiment with Florida Largemouth BassM. salmoides floridanusto evaluate the relative differences in survival, jaw mechanics, and feeding success after the use of three common handling treatments: (1) a vertical hold using a lip-grip device (vertical treatment); (2) a tilted, one-handed grip using only the lower jaw (horizontal treatment); and (3) two-handed support to the lower jaw and body (support treatment). The time taken by fish to regain equilibrium and resume normal swimming behavior after handling differed among the three treatments; the recovery period was shortest for fish in the support treatment (mean ± SD = 7 ± 10 s; vertical treatment: 33 ± 74 s; horizontal treatment: 12 ± 16 s). Minor injuries (e.g., abrasions and sores) and diseases (e.g., tumors and fungus) tended to increase after handling across the entire sample. Results suggested no evidence of handling-specific differences in fish feeding behavior, jaw adjustments, and mortality after release. However, based on our results, we recommend that anglers use two-handed support to handle Florida Largemouth Bass, thus minimizing the mean amount of time for an individual fish to regain equilibrium after an angling event. Received February 22, 2016; accepted October 7, 2016 Published online February 22, 2017 [ABSTRACT FROM AUTHOR]

The relative abundance of the largest size-classes of individuals within a fish population has an important influence on recruitment success. Fishing regulations with a basis in size (e.g., minimum-length limits) can directly impact the abundance of these larger individuals and thus potentially influence recruitment. We analyzed whether recruitment of exploited native Brown TroutSalmo truttapopulations was affected via the extraction of large individuals (>220 mm, i.e., minimum-length limit). The study was replicated temporally (2007–2009) and spatially across seven recreational fishing sections (four exploited and three catch-and-release sections) within the River Tormes located in central Spain. Catch-and-release sections were used as reference points to compare with exploited sections. We tested the hypothesis that minimum-length limit regulations would adversely affect fish recruitment through fishing-induced mortality of large individuals. Spawning stock (measured as fish >220 mm) and young-of-the-year abundances were estimated using multiple-pass depletion methods. We modeled the relationship between spawning stock and subsequent recruitment using a nonparametric approach (generalized additive models) to fit the best stock–recruit relationship. Additionally, von Bertalanffy growth and yield-per-recruit models were generated to evaluate the potential for growth and recruitment overfishing. The restrictive length limits used to regulate harvest in the study area limited both recruitment and adult abundance. The present study provides evidence that the use of minimum-length limit regulations in the management of recreational fisheries has the potential to adversely affect the species’ recruitment. Such adverse impacts could be occurring via both recruitment overfishing and growth overfishing, exemplifying that the removal of the larger size-classes of individuals through recreational fishing could have important consequences for recruitment. Management actions should be directed to protect large individuals (e.g., via harvest slots) rather than promote their removal, thereby reducing the chances of overfishing. Received November 25, 2015; accepted April 18, 2016Published online August 24, 2016 [ABSTRACT FROM AUTHOR]

Supplemental stocking of fingerling or advanced fingerling Largemouth BassMicropterus salmoidesis a common management strategy for augmenting natural production in low-recruitment systems. Few studies, however, have evaluated the impact of stocking adult bass taken from donor lakes. Over a period of 6 years, University of Florida researchers stocked Florida Lakes Griffin and Dora with 24,781 wild Florida BassM. s. floridanuscollected by electrofishing from other Florida lakes. During stocking years, stocked fish made up to 10% of the population in Lake Griffin and 27% in Lake Dora from electrofishing samples. However, 1 year after all stocked fish had been released, the proportion of stocked bass had declined to less than 5%, and 3 years after it had declined to less than 1%. We did not detect an increase in recruitment (catch of age-1 bass) following stocking, so any benefit from stocking was likely short-lived. We also could not conclude that stocking was responsible for increasing fishing effort because total fishing effort did not increase after stocking. As a result, no additive economic benefits could be attributed to the stocking program. During randomized electrofishing sampling, we collected 51 wild bass that had been released during the stocking program, and genetic analysis determined that two (3.9%) were hybrids and had alleles from nonnative Largemouth Bass. The extrapolation of these results estimated that almost 1,000 hybrids had been introduced into Lakes Griffin and Dora, which were historically identified to contain pure Florida Bass populations. Future wild bass stocking programs should include an appropriate study design for evaluating changes in fish populations, changes in the fishery, and economic consequences of stocking. Furthermore, a risk–benefit assessment should be completed before any stocking program is initiated, including consideration of any potential impacts on biodiversity. Received February 26, 2015; accepted January 6, 2016 Published online May 9, 2016 [ABSTRACT FROM PUBLISHER]

Fish populations that undergo heavy exploitation and those for which the act of fishing can influence individual brood success are at risk of recruitment effects due to angling. The angling of brood-guarding male black bassMicropterusspp. has been shown to decrease brood success, although there is no evidence that a loss of individual broods has population-level impacts. Therefore, some level of recruitment compensation may influence juvenile bass survival. We sought to measure recruitment compensation and the form of the stock–recruit relationship for a brood-guarding species, the Florida Largemouth BassM. salmoides floridanus(hereafter, Florida Bass). The study was conducted in four north-central Florida lakes during 4 years (2010–2013). We quantified adult stock density by using mark–recapture electrofishing surveys. The estimated broods produced in each spawning season, the number of those broods that were successful, and the age-1 recruit density were quantified via snorkel surveys. We evaluated three models for describing the effects of stock density or successful brood density on recruitment: a proportional (linear; i.e., no compensation) model, a Ricker (dome-shaped) model, and a Beverton–Holt (asymptotic) model. Recruit density was better indicated by the number of successful broods produced than by spawning stock density. Model comparisons indicated that the density-dependent models had the most support, whereas there was no apparent support for the proportional or density-independent model. The Ricker model had the most empirical support overall (estimated parameters:a= 2.2,b= 0.009). Our results indicate that the number of successful broods would have to fall below about 5 broods/ha to generate direct declines in observed average recruitment of Florida Bass. Received August 5, 2015; accepted December 9, 2015 Published online April 14, 2016 [ABSTRACT FROM AUTHOR]

Mortality after release can have a substantial impact on high-release recreational sport fishes, such as Largemouth BassMicropterus salmoides. However, little work has explored the cumulative impact of catch-and-release mortality at the population level. We used a combined telemetry–tag return approach to estimate all components of total mortality, including instantaneous natural mortality (M) and instantaneous fishing mortality (F), for Florida Largemouth BassM. salmoides floridanus(hereafter, Florida Bass) within a popular fishing lake in northern Florida. Fishing mortality was subdivided into harvest (FH), recreational catch-and-release (FR), and tournament catch-and-release (FT) components. Over 2 years, we monitored the fates of 181 Florida Bass that were tagged with high-reward external dart tags and internal radio transmitters. An additional 345 fish were tagged with variable-reward external tags. AnnualFHvalues were seasonal, with an increase inFHoccurring in the spring of both years;FHranged from 0.17 (SD = 0.04) in the first year to 0.60 (SD = 0.09) in the second year. Estimated meanFTranged from 0.04 to 0.07, and meanFRranged from 0.03 to 0.05. Estimates ofMwere also seasonal, with annualMranging from 0.29 (SD = 0.06) to 0.46 (SD = 0.09), and were within the expected range relative to other published estimates. Our results showed that although the total catch-and-release mortality (FRplusFT) was low in comparison with the high rates of harvest (FH) for this Florida Bass fishery, it still made up 21% of totalF. Our method combining passive tagging and telemetry tagging allowed for the estimation of all mortality sources, which can be important for high-release recreational fisheries in which harvest is not the only source of mortality. Received July 14, 2015; accepted December 7, 2015 Published online April 25, 2016 [ABSTRACT FROM AUTHOR]

Stocking evaluations for pellet-reared, advanced-fingerling Largemouth BassMicropterus salmoidesoften result in low contribution and survival, but little information exists on their survival and behavior soon after release. This study investigated the behavior and mortality of pellet-reared, advanced-fingerling (90–120 mm TL) Florida BassM. floridanusimmediately after they were stocked in Lake Carlton, Florida. A radiotelemetry experiment was conducted to compare initial movement, habitat use, growth, and mortality between stocked hatchery and wild fish. In year 1, we inserted radio transmitters into 50 hatchery fish; in year 2, we tagged 30 hatchery fish and 20 wild fish. All mortality we observed for hatchery fish (from both years) resulted from predation by fish and birds, and most occurred in the first 7 d after tagging. When compared directly with tagged wild fish (n= 20), tagged hatchery fish (n= 30) exhibited greater movement (75 and 124 m/d, respectively), greater proportion of locations offshore (8% and 23%, respectively), slower growth (1.73% and 0.41% of their body weight gained per day, respectively), and higher predation (47% and 0%, respectively). Results of this study suggest that pellet-reared, hatchery Florida Bass suffer more predation than wild bass of similar size initially following their release into the lake. Causes of predation could include less-developed antipredator skills and inefficiency in foraging observed through greater movement, as well as the use of offshore habitat and slower growth. We recommend research that investigates acclimating advanced-fingerling Florida Bass to predators and live prey before release to determine whether initial predation can be reduced after stocking. Received May 29, 2015; accepted December 4, 2015 [ABSTRACT FROM AUTHOR]

Background: Progressive dysexecutive syndrome (dAD) is an atypical presentation of early onset Alzheimer's disease (AD) with increased frontal and parietal region hypometabolism on FDG‐PET imaging compared to classic amnestic AD. We compared electroencephalogram (EEG) and FDG‐PET in dAD patients to determine if there was a correlation between EEG spectral activity and standard uptake value ratios (SUVR) in those regions. Method: FDG‐PET and resting state scalp EEG were obtained on AD‐biomarker confirmed, behavioral neurologist diagnosed cases of dAD (n = 11). We isolated awake‐eyes‐closed segments (mean duration: 113s, median:118s, range: 58‐138s) of each EEG and calculated the relative power of delta, theta, alpha, beta, and gamma bands within a wideband of 0.5‐40 Hz. In bilateral frontal and parietal regions, we averaged select channels across 6 to 14 10‐second windows per subject (fig.1). We evaluated the correlation between relative band powers and SUVRs of the regions by linear regression analysis. Result: There is a strong negative correlation (R2 = 0.54, p < 0.01) between alpha band relative power and SUVR in bilateral frontal regions (fig 2). Delta band relative power showed a strong positive correlation (R2 = 0.54, p < 0.05) with SUVR in the left frontal region. A positive trend was noted in the delta band in the right frontal region but did not reach statistical significance. Beta band relative power was negatively correlated with frontal region SUVR bilaterally, but only the left side reached statistical significance. These findings remained significant after multiple comparisons correction. No statistically significant correlations were noted in the parietal regions. Exploratory analysis revealed negative correlations between alpha bands and temporal region SUVRs bilaterally. Conclusion: In this small sample of selected individuals with dysexecutive AD, we report a strong correlation between EEG relative spectral power and PET regional SUVR in multiple EEG frequency bands and brain regions. In the bilateral frontal regions, slower delta frequencies and faster alpha and beta frequencies were associated with lower FDG‐PET signal. Future studies are needed to determine if this spectral power pattern and other EEG properties of dAD differ from other clinical dementia phenotypes and its clinical significance. [ABSTRACT FROM AUTHOR]

The Murray Cod Maccullochella peelii and Golden Perch Macquaria ambigua are important recreational species in Australia's Murray–Darling Basin (MDB); both species have declined substantially, but recovery is evident in some areas. Minimum length limits (MLLs)—implemented to ensure fish could spawn at least once prior to harvest eligibility—have increased three times in the past decade. We quantified variation in length at 50% maturity (LM50), age at 50% maturity (AM50), and von Bertalanffy growth parameters (k = Brody growth coefficient; L∞ = asymptotic length; t0 = theoretical age at zero length) of these species within two rivers and two reservoirs of the MDB; to investigate whether fish length is a suitable surrogate for AM50 in setting MLLs. Between 2006 and 2013, we collected 1,118 Murray Cod and 1,742 Golden Perch by electrofishing and gillnetting. Values of k and L∞ were greater for reservoir fish than for riverine fish. For both species, AM50 was generally greater in rivers than in reservoirs; for Murray Cod, LM50 was greater in reservoirs than in rivers. A yield‐per‐recruit model demonstrated that smaller Murray Cod MLLs would be required for rivers and that an MLL at or below 600 mm (the existing MLL) across all populations could lead to overfishing in some systems. The differences in growth rate and the onset of reproductive maturation between riverine and reservoir populations suggest that system‐specific regulations would be more effective at reducing the overfishing risk and meeting fishing quality objectives. Received August 18, 2014; accepted September 10, 2015 [ABSTRACT FROM AUTHOR]

Size‐at‐age information is critical in estimating growth parameters (e.g., the von Bertalanffy growth function [VBGF]) that are used to assess fish populations. Due to gear selectivity, single sampling methods rarely sample all ages or all sizes equally well. Most growth estimates rely on samples from a single gear or a haphazard combination of gears, potentially leading to biased and imprecise growth parameter estimates. We evaluated the efficacy of combining samples from two gears with different size selectivity to estimate VBGF parameters; we then applied that approach to a case study on the Lochloosa Lake (Florida) population of Black Crappies Pomoxis nigromaculatus. Simulated age‐ and size‐structured populations were randomly sampled with two gears characterized by different size‐selectivity curves (one gear was selective for smaller fish; the other was selective for larger fish). Maximum likelihood VBGF estimates obtained for each gear separately were compared with estimates from a combined VBGF fitted to data from both gears. In every simulated scenario, a combined‐gear approach reduced bias and increased precision for estimating the VBGF, but the gear‐specific proportions that improved VBGF estimates depended on size selectivity. The VBGF estimates for the Black Crappie population showed that the combined‐gear method yielded intermediate parameter values relative to single‐gear approaches based on (1) trawl sampling (fishery‐independent survey) and (2) angler harvest (as determined from carcass collections; fishery‐dependent data). Furthermore, the combined‐gear approach had greater precision in individual parameter estimates and much less variance than single‐gear approaches when estimating the VBGF. Combining data from two gears can increase sample representativeness, leading to improvements in VBGF estimation. Such approaches can reduce uncertainty in VBGF estimation and can provide insight into key demographic processes occurring in fish populations for which ontogeny and gear selectivity lead to imperfect sampling. Received January 22, 2015; accepted July 30, 2015 [ABSTRACT FROM AUTHOR]

Species-specific harvest regulations in recreational fisheries are commonly applied regionally to protect stocks from overharvest and satisfy a diverse set of anglers. While setting regulations is a complex task and may incorporate the best available social and biological information, fisheries managers commonly obtain directed fishing mortality estimates within a single lake and then assume similar rates among other systems when setting regional harvest regulations. Thus, there is a need to assess regional levels of fishing mortality for informed use of regionally applied regulations. We implemented a practical method for assessing catch and harvest for a recreational fishery across a broad spatial region. We used a passive tag-reward study design and a regional management regulation area for Florida Largemouth BassMicropterus salmoides floridanusin central Florida as our case study. The estimated fishing mortality rate included both harvest and deaths due to catch and release. We found overall regional fishing mortality for Florida Largemouth Bass in central Florida was relatively low. From the 247 dart tags returned, the mean annual instantaneous total fishing mortality rate was 0.11 (95% credible interval = 0.08–0.15). We also found fishing mortality rates did not vary with lake size or fish total length. Our study design did not provide mortality estimates for any specific lake due to a low number of tagged fish per lake, but the method could be used to elucidate the effectiveness of regulations that are applied at a regional scale. Received November 20, 2014; accepted March 31, 2015 [ABSTRACT FROM PUBLISHER]

Reduction in transmitter size used in telemetry studies have allowed researchers to tag and track fish that are much smaller than could have been tagged previously. Researchers seek information on juvenile or small fish movement, behavior, and survival to better understand recruitment processes. Juvenile or small-bodied fish that have been tagged have an increased risk of predation, which results in transmitters being consumed. Knowledge about radio transmitter accumulation in a predator's gut and evacuation times are critical for interpreting locations of radio-tagged fish and their predators. Our objective was to determine what factors influenced the evacuation time of transmitters (0.3 g), implanted in juvenile Largemouth BassMicropterus salmoidesthrough the digestive system of adult Largemouth Bass that had preyed upon those tagged juveniles. All transmitters ingested by the predators were evacuated within 84 h. A Poisson regression model showed that transit time decreased significantly with temperature and increased with prey length and predator length. The results of this study suggest that miniature radio transmitters (e.g., 0.3 g) do not accumulate in the digestive tract of predators and that after consumption, up to 3 d of behavior (i.e., movement and habitat use) by the predator, movements could falsely be attributed to the juvenile fish. Therefore, if a distinction cannot be made between predator and tagged juvenile Largemouth Bass, we recommend not including information from the final 3 d before cessation of movement when analyzing the behavior of tagged fish. Received June 9, 2014; accepted January 28, 2015 [ABSTRACT FROM PUBLISHER]

We examined seasonal dynamics of prey availability and diets of Largemouth BassMicropterus salmoidesin the St. Johns River, Florida. The four most common prey species were Threadfin ShadDorosoma petenense, Bay AnchovyAnchoa mitchilli, Atlantic CroakerMicropogonias undulatus, and Atlantic MenhadenBrevoortia tyrannus. The number of prey found in Largemouth Bass varied significantly by month (year-round) and predator size (“small,” <356 mm TL,n= 267; “medium,” 356–432 mm TL,n= 205; “large,” >432 mm TL,n= 114). Atlantic Menhaden were most energetically beneficial to predators when available. Of the four most common prey species collected in trawls, only menhaden trawl catch was positively correlated with its appearance in bass diets. Menhaden were eaten by bass of all sizes, but were found only from September through November. Largemouth Bass did not feed heavily on juvenile anadromous shadsAlosaspp. during their autumn migration, but this likely reflected low abundance of these clupeid species. The seasonal diversity of prey available in the St. Johns River may contribute to its being one of the most productive Largemouth Bass fisheries in Florida. Received June 23, 2014; accepted October 22, 2014 [ABSTRACT FROM AUTHOR]

Recent advances in the technology of miniature radio transmitters have allowed researchers to study smaller fish, including juveniles, for which behavioral information is lacking. Transmitters selected should have minimal effects on tagged fish so that inferences may be made about untagged individuals. Our objective was to evaluate the short-term effects of surgically inserted dummy transmitters (1.2–2.7% of the fish's body weight) on growth and predator avoidance in 90–120-mm hatchery-reared Largemouth BassMicropterus salmoides.We compared growth and predator avoidance between tagged and untagged (control) fish in tanks. Mortality of tagged and control fish was variable by tank and was most commonly caused by columnaris, a fish disease widespread in aquaculture. A slight impairment of growth for tagged fish (difference of as much as 1.19% body weight gained per day) was observed during experiments run for 21 and 30 d. At the conclusion of each growth experiment, most fish had shed their suture and incisions had completely healed. No incidents of transmitter expulsion occurred in either growth experiment. During the predation trials, 49% of both tagged fish and controls were eaten by predators, suggesting that the radio tags did not affect the fish's vulnerability to predation. Despite some mortality observed in the laboratory and slight growth impairment in tagged fish, predation studies implied that the ability to avoid predators was not affected in tagged individuals. Therefore, we conclude that surgical implantation of radio transmitters can be a valid tagging technique for examining the behavior of juvenile Largemouth Bass in short-term field studies. Received June 14, 2013; accepted October 7, 2013 [ABSTRACT FROM AUTHOR]

Few studies have explored annual reproductive effort of fish populations, yet factors such as skipped spawning could influence recruitment processes. We estimated the number of broods produced annually as an index of reproductive effort for Florida BassMicropterus floridanusacross four lakes in north-central Florida. Snorkel surveys were used to estimate reproductive effort in the lakes from 2010 to 2012. Mark–recapture methods were used to estimate the abundance of Florida Bass in each lake during each year. All four lakes contained high-density Florida Bass populations that showed evidence of relatively slow growth. Average relative weight in all populations was low, ranging from 65.4 to 68.8 for adults (≥25.0 cm TL). Annual reproductive effort (estimated number of broods) varied among lakes and across years. We found evidence for multiple spawning events per adult and for skipped spawning. Devils Hole Lake produced the highest number of broods in all 3 years, ranging from 1.62 broods/spawner in 2012 to 3.72 broods/spawner in 2011 (median = 3.24 broods/spawner in 2010). All other populations exhibited skipped spawning, with the proportion of nonreproductive adults varying across years. Picnic Lake fish had the lowest number of broods overall (only 0.02 broods/spawner in 2011 and 0.01 broods/spawner in 2012). The other two lakes showed variable levels of spawning effort. Spawner abundance in these populations was not related to the estimated annual number of broods, contrary to the general assumption made for many population models. Variability in annual reproductive effort may be more common than anticipated, potentially clouding the relationship between spawner abundance and recruitment. Estimation of annual reproductive effort may provide insight into density-dependent population regulation and recruitment processes. Received February 14, 2013; accepted July 22, 2013 [ABSTRACT FROM AUTHOR]

Fisheries assessments often rely on age composition data to infer information about growth, mortality, and the outcome of various management policies. To reduce the costs of estimating the age of all fish collected (i.e., via direct aging), an age–length key (ALK) is often developed by directly aging only a subsample of fish and estimating the ages of the remaining fish based on observed lengths. Although this approach is common, there is little guidance in the literature for determining the appropriate total sample size and numbers of fish needed to directly age for each length bin. We developed a stochastic simulation to evaluate the sample-size requirement for using ALKs to estimate von Bertalanffy growth parameters and the instantaneous rate of total mortality (Z). The simulations accounted for variation in life history characteristics of stocks and exploitation rates of fisheries. Our simulations suggested that for overfished populations, aging more fish per bin provides negligible benefits whereas collecting larger total sample sizes could improve bias and precision ofZestimates. These results also indicated that bias and precision was relatively uninfluenced by fish life history type, which may allow for standardization of field collection methods across a wide range of fish species. In most cases, total sample sizes of 500–1,000 and 10 fish aged per bin provided near optimal performance in accuracy and precision, suggesting that this could be a guideline for many studies. Received August 21, 2012; accepted January 14, 2013 [ABSTRACT FROM PUBLISHER]

Electrofishing CPUE data are commonly used to index temporal trends in abundance in fish monitoring programs, but the reliability of this index requires the assumption that the fraction of fish stock caught per unit effort (catchability, q) is relatively precise and constant through time. We evaluated how fish species, season, and lake affected electrofishing catchability in Florida lakes using a field study. We used the field study results to simulate how variable electrofishing q affects statistical power and type I error rate (i.e., the probability of detecting a difference when in fact no difference occurred). Model selection showed that electrofishing catchability varied by species, season, and lake, and submodels showed that catchability varied by lake for Largemouth Bass Micropterus salmoides and by season for Lake Chubsucker Erimyzon sucetta, and was constant across season and lake for Bluegill Lepomis macrochirus. Our results revealed that statistical power decreased and the type I error rate increased substantially if q varied through time as we observed for Largemouth Bass and Lake Chubsucker. Type I error rates were well above the expected value of 0.05, reaching as high as 0.7 for Largemouth Bass and 0.55 for Lake Chubsucker at high sample sizes. This resulted because increasing sample size improves the ability to detect real changes, but also increases the probability of detecting spurious changes due to variable q (i.e., type I error). Thus, variable catchability hinders our ability to use CPUE data to index trends in fish abundance, and monitoring programs should consider how q varies before relying on CPUE data to index fish abundance. [ABSTRACT FROM AUTHOR]

Trophy-size fish are a critical component of recreational Largemouth Bass Micropterus salmoides floridanus fisheries; therefore, many agencies have prioritized management actions to improve catches of large fish. Length-based harvest regulations are commonly used to increase the abundance of trophy-size fish, but the rarity of large fish in sampling programs makes it difficult to use field data to evaluate the effectiveness of those regulations. We used an age-structured simulation model parameterized for a trophy Largemouth Bass fishery to evaluate the potential for a range of size limits to increase abundance and angler catches of trophy Largemouth Bass (>610 mm TL). We compiled creel information from four Florida lakes with varying harvest regulations that were known to have high-quality trophy fisheries in order to assess the performance of the model. Model results were scaled to represent trips per trophy catch for a range of size limits. The model predicted that the average number of angler trips required to catch a trophy fish were expected to decline from 83 under a 350-mm minimum length limit (e.g., baseline model that represents the standard length limit in the peninsula of Florida) to 47 for a 600-mm minimum length limit if exploitation rates were 0.2. Maximum size limits and protective slot limits also showed potential to substantially improve trophy catches. The model results and creel estimates showed similar trends for the predicted number of angler trips required to catch a trophy fish on lakes managed for trophy Largemouth Bass in Florida. Our model could be combined with fish population data to forecast the effectiveness of regulation changes on trophy fish catches. This could provide insight into trophy fisheries, where field measurements of trophy abundance and angler catches are difficult to obtain with traditional sampling programs. [ABSTRACT FROM AUTHOR]

The bull trout Salvelinus confluentus is an apex predator in native fish communities in the western USA and is listed as threatened under the U.S. Endangered Species Act (ESA). Restoration of this species has raised concerns over its potential predatory impacts on native fish fauna. We held a five-person expert panel to help determine potential impacts of reintroducing bull trout into the Clackamas River, northwest Oregon, on the viability of four anadromous salmonid populations that are listed as threatened under the ESA: spring and fall Chinook salmon Oncorhynchus tshawytscha, coho salmon O. kisutch, and winter steelhead O. mykiss. The panel session was rigorously structured and used a modified Delphi process with structured expert elicitation, disclosure, discussion, and brainstorming. Each panelist distributed 100 score points among seven categories of potential bull trout impact (from no impact to very high impact) on extinction probabilities for the anadromous salmonids. Results were provided by individual panelists rather than as a group consensus and were summarized as means and variations in scores to express the panelists’ individual uncertainty, variability among the panelists, and expected differences among the affected salmonids. Score results suggested that panelists viewed the potential impact of bull trout as very low or moderately low for spring Chinook salmon, coho salmon, and winter steelhead and mostly none to very low for fall Chinook salmon. Panelists also provided 19 possible monitoring activities and 21 possible management actions for assessing potential impacts and taking remedial action if bull trout are found to have unacceptable adverse effects. Results of the panel were used by the U.S. Fish and Wildlife Service to help craft and execute a plan to reintroduce bull trout into the Clackamas River system under the ESA. This rigorous expert panel process can be used for a wide range of evaluations in situations where empirical data are sparse or ecological interactions are too complex for explicit analytic solution. Received September 5, 2011; revised December 12, 2011; accepted January 3, 2012 [ABSTRACT FROM AUTHOR]

Gizzard shadDorosoma cepedianumhave been the target of removal efforts in eastern North American lakes due to their omnivorous feeding, which may increase nutrient cycling and contribute to high phytoplankton abundance. We used a simulation model to evaluate the efficacy of a gizzard shad removal program at the Harris Chain of Lakes (HCL), Florida, by testing the effects of the exploitation rate, gill-net mesh size, and harvest interval on the total population biomass and spawning potential ratio (SPR). The analysis accounted for compensatory density dependence of the gizzard shad population and uncertainty in life history parameters. The reductions in gizzard shad biomass and SPR were less than 50% for the two largest mesh sizes (89 and 102 mm) at realistic annual exploitation rates of 0.6–0.8. However, the use of smaller mesh sizes (51 and 64 mm) produced biomass and SPR reductions that exceeded 75% at comparable harvest rates. Current removal efforts at the HCL, which employ a minimum gill-net mesh size of 102 mm, are unlikely to reduce gizzard shad biomass substantially. However, smaller mesh sizes could result in increased bycatch of economically important black crappiesPomoxis nigromaculatus. Our study sheds light on the importance of using simulation models to forecast the effects of removal efforts on target fish species. The results of such models can be used to inform harvest practices to achieve desired outcomes. Received May 12, 2011; accepted September 12, 2011 [ABSTRACT FROM PUBLISHER]

Understanding the relationships between river discharge and recruitment of estuarine fishes is important because of hydrological alterations caused by anthropogenic water withdrawals. Varying river discharge alters salinity, turbidity, nutrient levels, and detrital concentrations, all of which affect estuarine biota. The lower Suwannee River, Florida, is one of the few remaining large-river systems in the United States that has no major impoundments. We assessed the relationship between seasonal river discharge and relative abundance, growth, and mortality of estuary-dependent age-0 fish of five species in the Suwannee River estuary. We analyzed 9 years of data (1997-2005) collected as part of a long-term, fishery-independent monitoring program. The results showed a positive relationship between relative abundance and river discharge for age-0 spotted seatrout , sand seatrout , and red drum . The pinfish was the only species for which relative abundance was negatively related to river discharge; the relative abundance of spot was not significantly related to changes in discharge. Instantaneous daily growth ( G) estimates were positively related to river discharge for all species except spotted seatrout, for which a negative correlation was found. Instantaneous daily mortality ( Z) estimates were positively correlated with river discharge for sand seatrout, pinfish, and red drum. The G : Z ratios for pinfish and early recruiting sand seatrout were negatively related to river discharge, indicating that recruitment potential declined with higher discharge. Changes in freshwater discharge affected the abundance, growth, and survival of these juvenile fishes, stressing the importance of water allocation decisions that affect estuarine fishes and the fisheries they support. [ABSTRACT FROM AUTHOR]

The golden perch Macquaria ambigua is a recreationally important freshwater sport and food fish species found throughout southeastern Australia. Stocking golden perch in impoundments has been used by fisheries managers to enhance existing wild populations for over 30 years. Despite widespread stocking, the contribution of stocked fish to golden perch populations has not been investigated. We evaluated the stocking contribution by using chemically marked golden perch fingerlings introduced into three lakes in which natural recruitment is low. We surveyed the lakes to determine the contribution of the stocked fish to the lake populations and found an overall contribution of 47 ± 9% (mean ± SE) at Reedy Lake, 55 ± 9% at Kangaroo Lake, find 90 ± 5% at Lake Charm. Our results indicate that, rather than replacing wild fish, stocked fish increased the abundance of adult fish at all three lakes. The contribution of stocked fish to each population declined with increased connectedness to the Loddon River, which served as the probable source for the wild fish population. Stocking programs can substantially augment fish populations when natural recruitment is very low. [ABSTRACT FROM AUTHOR]

We used an age-structured model to evaluate the impacts of recreational angling during spawning on populations of largemouth bass and the potential benefits of seasonal fishing closures. We simulated fisheries with average and high capture rates (i.e., fractions of the stock caught by anglers). We manipulated mortality rates to mimic the effects of various regulations, including (1) an open fishery with no closures, (2) a full fishery closure during the spawning season, (3) a catch-and-release fishery during the spawning season, and (4) a year-round catch-and-release fishery. We simulated two hypothetical populations: a high-productivity, low-latitude population and a low-productivity, high-latitude population. Spawning season closures produced the largest relative increases in adult abundance when applied to low-productivity populations and when capture rates were high (e.g., 70%) and harvest rates were relatively low (20%). This resulted because very high capture rates imply that most spawning fish will be caught by anglers and potentially lose their broods to nest predators. The existing evidence suggests that these conditions (very high capture rates combined with low harvest rates) are the exception rather than the rule across largemouth bass fisheries. Understanding capture and harvest rates is critical to the use of seasonal closures in recreational fisheries. [ABSTRACT FROM AUTHOR]

Rapid human population growth and an associated increase in consumptive water demands within the ecologically diverse Apalachicola-Chattahoochee-Flint (ACF) River basin of the southeastern United States have led to a series of highly publicized water wars, exacerbated by recent drought conditions, between the states of Alabama, Georgia, and Florida. A key issue is how managing riverine flows to meet human water needs will affect the viability of species that are federally listed as threatened or endangered, including the Gulf of Mexico sturgeon Acipenser oxyrinchus desotoi. Our present understanding of Gulf sturgeon ecology within the Apalachicola River basin indicates that altered riverine flow regimes may affect spawning success and possibly the recruitment patterns of the population. Through intensive field work, we documented Gulf sturgeon spawning site selection in the Apalachicola River and then evaluated the relationship between river stage and the available spawning habitat at these sites. We then used an age-structured simulation model to assess the effects of changes in recruitment patterns on population viability using hypothetical scenarios based on changes in flow regime and its effect on available spawning habitat. Over 3 years we were able to collect almost 500 Gulf sturgeon eggs in the Apalachicola River at three different spawning sites. We observed that the depths and flows where eggs were found were similar across years and sites despite varying river conditions. River discharges of less than 142 m3/s at Jim Woodruff Lock and Dam significantly reduced the spawning habitat available to Gulf sturgeon at all known spawning sites, potentially affecting recruitment. Gulf sturgeon populations are probably sensitive to changes in recruitment, and if extreme low-flow events occur with increasing frequency owing to water management policy choices or climatic events, population recovery could be impaired and the risk of extirpation could increase. Managers should consider the potential effects on Gulf sturgeon recruitment when determining future flow regime policies within the ACF. [ABSTRACT FROM AUTHOR]

Commercial bycatch can potentially induce high fishing mortality and represents serious concerns for the sustainability of some fisheries. We evaluated the potential population-level impacts of commercial gill-net bycatch and recreational fishing mortality on black crappie Pomoxis nigromaculatus in Lake Dora, Florida. We assessed total black crappie bycatch and the mortality rates of black crappie entangled in gill nets, quantified recreational fishing effort and harvest, and estimated exploitation for the recreational and commercial (bycatch) fisheries. We used an equilibrium age-structured population model to assess potential population-level impacts of bycatch and recreational fishing mortality. Onboard observer data of commercial fishers showed that about 17,000 and 30,000 black crappie were captured in gill nets in 2005 and 2006, respectively. Cage experiments revealed that about 30% and 47% of black crappie captured in gill nets experienced mortality after 72 h in 2005 and 2006, respectively. The recreational fishery exploitation rate was estimated to be 42% based on angler tag returns in 2006, and commercial exploitation via bycatch from commercial gill nets was 15%. The population model suggested that the level of recreational fishing mortality observed in 2006 was probably sustainable but that additional commercial or recreational exploitation would create a risk of recruitment overfishing. The greatest risk for recruitment overfishing via bycatch occurs when other sources of exploitation are also high (e.g., via a recreational fishery). [ABSTRACT FROM AUTHOR]

We built a simulation model to assess the performance of catch-curve residuals as an index of year-class strength for a short-lived and a long-lived fish life history type across a range of assumed values for the variation in recruitment (CVR) and fishing mortality (CVF). The magnitude of CVR strongly influenced the utility of catch-curve residuals in assessing year-class strength. The probability, of finding a significant correlation between catch-curve residuals and true recruitment values exceeded 0.9 when CVR was greater than 0.5 for the long-lived and greater than 1.0 for the short-lived life history types. This suggests that larger recruitment values have a greater probability of being successfully "tracked" through the age structure. Conversely, the magnitude of interannual variation in fishing mortality weakly influenced the performance of catch-curve residuals. The inspection of individual catch-curve residuals relative to the known recruitment values that produced them showed considerable scatter, indicating that the utility of this metric in assessing individual year class strength is small. Sensitivity analyses showed that the performance of catch-curve residuals improved modestly with equal sampling vulnerability across ages and decreased slightly with increased fishing mortality. Our results suggest that catch-curve residuals can serve as a rudimentary measure of recruitment under ranges of recruitment and mortality variation similar to those frequently observed in field studies. [ABSTRACT FROM AUTHOR]

Latitudinal influences on growing season length and winter severity cause variation in prerecruitment life history across species distributions. We evaluated two recruitment hypotheses for a broadly distributed species, largemouth bass , at the southern extent of their natural range. We tested (1) whether early hatching provided a growth and survival advantage relative to later hatching through their first summer and (2) whether overwinter size-selective mortality strongly influenced recruitment to age 1 across Florida's latitudinal gradient. We sampled the 2003 and 2004 year-classes at six Florida lakes that spanned latitudes from 27°0′N to 30°5′N. Our results did not fully conform to our hypotheses or the results frequently reported from more northerly latitudes because largemouth bass that hatched early did not exhibit a growth and survival advantage at all lakes and we did not detect strong size-selective overwinter mortality. Early hatching at south Florida lakes resulted in slow growth for three of four lake and year combinations and early-hatched fish never exhibited a survival advantage relative to later-hatched fish, which was probably due to cool water temperatures soon after hatching. Environmental variability influenced the interactions between hatching period, growth, and survival for Florida's largemouth bass populations, which has implications for understanding fish recruitment across broad spatial scales. [ABSTRACT FROM AUTHOR]

Standardized protocols for sampling fish in lentic systems were recently established for the Florida Fish and Wildlife Conservation Commission. One of the main concerns of state biologists is that standard sampling methods could reduce the value and comparability of long-standing, fixed-transect historical data sets. Therefore, largemouth bass Micropterus salmoides were sampled by electrofishing in six lakes using both the historical and the new standard methods in spring 2006. Based on a two-way analysis of variance, the mean log-transformed catch per unit effort (CPUE) and proportional size structure of quality-size fish (PSSQ) and preferred-size fish (PSSP) did not differ significantly between the two sampling methods for any lake, when all samples were included. Based on bootstrapping analyses, which controlled for differences in sample sizes between the standard and historical methods, the variation associated with mean CPUE was generally higher for the standard method, whereas the variation associated with mean PSSP was generally higher for the historical method. Aside from PSSQ, the sample size required to obtain adequate levels of power and detection were met only by the standard method, for which a larger number of samples were collected. Our study suggests that the point estimates (i.e., means) from the historical methods can be used in trend analyses in concert with the new standard methods but that the standard method provides for better comparisons among water bodies. [ABSTRACT FROM AUTHOR]

We reviewed estimates of annual exploitation (u) and total mortality (Z) for populations of largemouth bass Micropterus salmoides and used a simulation model to explore how temporal changes in u have influenced those populations. The review produced 32 estimates of u and 30 of Z spanning 51 years. Fishing mortality was roughly parabolic through time, with a mean of 0.35 for 1976-1989 and a mean of 0.18 for 1990-2003. Thus, average fishing mortality rates have declined by about one-half since about 1990. Total mortality declined with the decline in u, suggesting that changes in u caused lower overall total mortality rates. The evidence further suggests that the decline in u was caused by the voluntary release of fish by anglers rather than by changes in overall fishing effort. The simulation model showed that the decline in exploitation increased adult largemouth bass abundance but reduced the ability of size and bag regulations to improve population metrics owing to low rates of directed harvest. Discard mortality (i.e., the mortality of fish caught and released) would not negate the benefits of lower exploitation unless the mortality of fish caught and released was 0.3 or higher. Changes in angler behavior have substantially reduced fishing mortality for largemouth bass fisheries, which should be considered when developing management plans for this species and others with high rates of voluntary release. [ABSTRACT FROM AUTHOR]

Abundance of the spotted sunfish has been positively correlated with interannual fluctuations in river stage, making this a potential indicator species for streamflow management. We evaluated patterns of habitat selection by adult and juvenile spotted sunfish and related them to simulated declines in river stage at three southwestern Florida rivers (Anclote, Little Manatee, and Manatee rivers). To identify habitat selection patterns, we used multivariate analysis of variance to compare measured characteristics (i.e., current velocity, depth, and cover abundance) of habitats used by spotted sunfish with those of randomly located habitats within the stream margin environment. Spotted sunfish generally selected habitats with greater structural complexity than the average available habitat. In many instances, spotted sunfish appeared to select habitats that contained both large and fine woody debris. However, fish were collected from a variety of habitat types during the study, indicating that this species is somewhat general in its habitat use. We found few significant differences in habitat measures between juvenile and adults, suggesting that habitat selection was similar between these life stages. Our model simulations indicated that 0.3-m reductions in average daily river stage could reduce habitat availability for spotted sunfish by 20-70% across systems. Spotted sunfish used habitats with greater-than-average resiliency to stage declines (i.e., deeper, more complex habitat). Considering that even minor reductions in the average daily stage during fall and spring could substantially reduce overall availability of suitable habitat, the inundation of complex habitat types is probably important for spotted sunfish. [ABSTRACT FROM AUTHOR]

American shad , hickory shad , and blueback herring spawn in Florida's St. Johns River during winter and spring, and juveniles migrate out of the estuary during the following fall. We assessed the temporal trends of juvenile relative abundance and size as each species moved downstream past Palatka, Florida, and compared these values to historical data from the system. Juveniles were collected from April 2004 to March 2005 primarily with surface trawling at night and with supplemental daytime electrofishing. Relatively few juveniles were collected by trawl (23 American shad, 7 hickory shad, and 36 blueback herring) or by electrofishing (55 American shad, 4 hickory shad, and 179 blueback herring). Trawl catch rates were highest in autumn, and electrofishing catch rates were highest in autumn and early winter. Both sampling methods caught juveniles at similar sizes. The surface trawl catch rates of juvenile American shad in 2004 and 2005 were not significantly different from comparable historical catch rates for 1969 and 1970, suggesting similar overall juvenile recruitment levels. Trawl collections were sufficient to document the seasonal downstream migration of shad juveniles. However, given the low catch rates, we found electrofishing to be a useful alternative method for describing seasonal abundance and habitat use by juvenile shad. [ABSTRACT FROM AUTHOR]

We evaluated the effects of variable flows on water chemistry and fish communities to recommend biologically based minimum flows that protect low-salinity zones for freshwater-oligohaline (FO) fishes below the Hillsborough River Dam, Tampa, Florida. We plotted the distributions of hypoxic (dissolved oxygen [DO] ≤ 4 mg/L) and meso- and polyhaline (salinity > 5‰) habitats and evaluated changes in species richness and spatial distributions of FO fishes on five sampling dates from October 2002 to July 2004. During low flows (0.12 m³/s; <25th percentile) in May 2004, oligohaline habitat was reduced as a salt wedge (>5‰) migrated upstream to within 1,300 m of the dam and DO decreased to less than 4 mg/L in the lower part of the reach. However, intermediate (1.19-2.18 m³/s; 25th-50th percentiles) and high flows (5.49 m³/s; 50th-75th percentiles) on four of the five sampling dates maintained oligohaline salinities (i.e., ≤5‰) and DO greater than 4 mg/L throughout most of the reach. Using fyke net data, we found no flow-related trends in FO fish species richness. However, spatial occurrence data indicated that the distribution of FO fishes shifted upstream to within 1,660 m of the dam during a low flow in May 2004. Thus, FO fishes may have congregated in the upper part of the reach or moved out of the lower reach because of unsuitable water quality during low flows. Our results suggest that the best minimum flow to preserve obligate freshwater and oligohaline fishes in the lower Hillsborough River would be between 0.12 m³/s, which eliminated freshwater and reduced oligohaline habitat, and 1.19 m³/s, which provided freshwater and oligohaline habitat throughout most of the study reach. Freshwater flows below the Hillsborough Dam influenced salinity gradients and the spatial occurrence of FO fishes in this system. Low-salinity habitats and FO fish taxa should be considered when setting minimum flows for estuaries. [ABSTRACT FROM AUTHOR]

Growth, annual exploitation (u), and natural mortality (v) of bluegills Lepomis macrochirus and redear sunfish L. microlophus were investigated on Lake Panasoffkee, Florida, during 1998 and 1999 to assess the potential benefits of several minimum size limits. The average u of 15.0-cm total length (TL) or larger fish was 0.14 for bluegills and redear sunfish during the 2-year period. For both species, exploitation increased up to threefold as fish size increased (e.g., u = 0.37 for bluegills ≥ 23.0 cm TL in 1999). Total annual mortality (A) was 0.64 for bluegills and 0.68 for redear sunfish. Natural mortality estimates were 0.50 (78% of A) for bluegills and 0.55 (81% of A) for redear sunfish. Simulations predicted that minimum size limits would decrease average total yield and harvest for both bluegills and redear sunfish, but that a 20.3-cm minimum length limit could slightly increase the number of fish harvested over 20.0 cm TL. A 22.9-cm minimum length limit was predicted to greatly reduce yield without creating a measurable increase in the harvest of fish over the size limit. Lake Panasoffkee sunfishes incurred record levels of estimated effort and harvest in 1998-1999, but size-selective exploitation acted essentially as a minimum size limit, resulting in no predicted benefit for a 20.3-cm limit. Separation of fishing mortality and natural mortality allowed us to conclude that natural mortality had a greater influence on Lake Panasoffkee sunfish population abundance and fishing quality than did fishing mortality, so a minimum size limit was not recommended. Estimates of exploitation, natural mortality, and growth rates are more valuable than measures of size structure and angler catch when considering or evaluating harvest restrictions. [ABSTRACT FROM AUTHOR]

In an effort to aid in the conservation of black basses, the relative abundance, growth, and mortality of Suwannee bass Micropterus notius and largemouth bass M. salmoides were estimated from four Florida rivers. Fish were collected by electrofishing in the four rivers during 2001 and 2002. Electrofishing catch per unit effort of Suwannee bass was highest in the Wacissa River (95.1 fish/h), intermediate in the Santa Fe River (22.6 fish/h), and lowest in the Withlacoochee (5 fish/h) and Ochlockonee rivers (1.9 fish/h). Catch per unit effort for largemouth bass was also highest in the Wacissa River (50 fish/h), intermediate in the Santa Fe (19.8 fish/h) and Ochlockonee rivers (17.1 fish/h), and lowest in the Withlacoochee River (9.9 fish/h). Mean total length (TL) at age across the four Suwannee bass populations was described by von Bertalanffy growth curves as TL = 386.1 ⋅ (1 - e-0.3733[age+0.7772]) for females and as TL = 324.1 ⋅ (1 - e-0.4735[age+0.6543]) for males. Mean TL at age across the three largemouth bass populations was also described by von Bertalanffy growth curves as TL = 644.2 ⋅ (1 - e-0.2064[age+0.9840]) for females and TL = 427.8 ⋅ (1 - e-0.3164[age+0.9991]) for males. Suwannee bass exhibited sex-specific growth rates similar to those of largemouth bass, females experiencing more rapid growth and attaining larger sizes than males (F1, 564 = 20.39; P < 0.01). Suwannee bass total annual mortality (A) averaged 40%, ranging from 28% to 46%. Similarly, largemouth bass total A averaged 40%, ranging from 35% to 46%. The current Florida minimum length limit on Suwannee bass directs fishing mortality almost solely to females, but estimates of fishing mortality are needed to determine whether this is a concern for black bass with a small native range. [ABSTRACT FROM AUTHOR]

Crappies spp. are popular sport fishes but are often difficult to manage due to highly variable recruitment. To assess the factors influencing recruitment, we investigated the size and abundance of age-0 black crappie in relation to zooplankton density, adult stock abundance, and water clarity in three productive Florida lakes. Age-0 black crappies were collected at Lakes Wauberg, Lochloosa, and Tarpon by use of surface and bottom trawls during the spring, summer, and fall of 2000 and 2001. Zooplankton abundance was measured concurrently with trawl sampling. Early-summer juvenile abundance was positively related to stock abundance during the previous fall among lakes, indicating a relationship between stock size and juvenile black crappie abundance. Early-summer juvenile abundance was positively related to juvenile abundance in the fall (i.e., at the end of the first summer), suggesting that year-class strength was set by early summer in all lakes. Lake Lochloosa had the highest crustacean zooplankton abundance in both years, but this lake had the smallest age-0 black crappie size and intermediate age-0 fish abundance. Thus, we found no relationship between crustacean zooplankton density and black crappie size across lakes. Reduced Secchi depths due to high chlorophyll- a values and wind resuspension of sediments may have reduced feeding efficiency for age-0 black crappies at Lake Lochloosa relative to the other lakes. Age-0 black crappie abundance and size during fall were not predicted solely by food availability, stock abundance, or water clarity, suggesting that these factors interacted to influence recruitment through the first year of life. [ABSTRACT FROM AUTHOR]

We used creel survey data combined with a simulation model to assess how tournament-associated mortality could increase exploitation of largemouth bass Micropterus salmoides and influence largemouth bass fisheries. We obtained estimates of total largemouth bass harvest (HARV) and total tournament catch (TC, i.e., the number of fish brought to judging stations) at nine lakes from Arkansas, Florida, and Texas. The ratio of TC to HARV exceeded 1.0 at five of the nine lakes studied and ranged from 0.35 to 5.18. We simulated potential tournament-associated mortality rates ranging from 0% to 70% applied to TC fish. Because exploitation was not known, we modeled harvest estimates to represent four potential exploitation rates (5, 15, 25, and 35%). The age-structured simulation model predicted that at three of nine lakes where TC/HARV ratios exceeded 3.0, tournament-associated mortality rates of 20-30% could cause 5-12% declines in the abundance of largemouth bass larger than 300 mm total length and resulted in declines in population size structure. At lakes with TC/HARV ratios of less than 1.0 (N = 4 lakes), the model predicted that tournament-associated mortality would have a negligible impact (i.e., ≤5%) on the abundance of adult fish and population size structure, regardless of the tournament-associated mortality rate. Tournament-associated mortality may not significantly influence most largemouth bass fisheries. However, in lakes where tournament catch was substantially higher than harvest, tournament-associated mortality could encompass a large portion of fishing-associated mortality and would influence largemouth bass fisheries if harvest estimates corresponded to exploitation rates of 15% or more. Exploitation measures based solely on harvest may not reveal significant portions of fishing-associated mortality for fisheries where tournament catch can exceed harvest. [ABSTRACT FROM AUTHOR]

Evaluates the abundance of largemouth bass Micropterus salmoides before and after a habitat enhancement project at Lake Kissimmee, Florida. Factors behind the degradation of fish habitat; Estimation of the age frequencies of largemouth bass; Improvement in the electrofishing catch rates of largemouth bass.

We investigated the macrohabitat use, microhabitat use, and food habits of shoal bass and largemouth bass in the upper Chipola River, Florida. We electrofished two macrohabitats (pools and shoals) during the summer (May-August) and fall (September-December) of 1999 and 2000. The ratio of shoal bass to largemouth bass differed among macrohabitats, being highest in the shoals and lowest in the pools. Age-0 and adult (age-1 and older) shoal bass were collected in areas of higher-than-average percentages of rocky substrate in both shoals and pools. Age-0 and adult largemouth bass were associated with areas of reduced current velocity and those with higher-than-average amounts of woody debris. Though the diets of age-0 and adult shoal bass and largemouth bass were similar, a few differences were apparent. Age-0 largemouth bass diets contained grass shrimp spp., whereas age-0 shoal bass diets contained mostly mayflies (order Ephemeroptera: families Baetidae and Isonychidae). Crayfish and fish were the primary food resources of adult shoal bass and adult largemouth bass, and crayfish became more prevalent than fish in larger individuals of both species. Largemouth bass transitioned to a crayfish-dominated diet at a smaller size than did shoal bass. Considering that we found substantial differences in the habitat associations of these species but relatively few diet differences, habitat partitioning may be important for the coexistence of shoal bass and largemouth bass in rivers and streams. Future shoal bass conservation efforts should focus on maintaining a diversity of habitats where these species coexist and on protecting relatively rare shoals. [ABSTRACT FROM AUTHOR]

The Suwannee River, Florida, population of the Gulf of Mexico sturgeon Acipenser oxyrinchus desotoi, a subspecies of Atlantic sturgeon A. oxyrinchus oxyrinchus, was evaluated using a capture-recapture approach and an age-structured model to examine population trends from 1986 through 1995. The capture-recapture analysis revealed a positive rate of change (λ) in the adult population, indicating that it was slowly increasing from the mid-1980s through the mid-1990s. The age-structured model revealed that the population was highly sensitive to changes in egg-to-age-1 mortality, the percentage of females that spawn annually, and adult mortality. The model predicted that even slight increases in annual adult mortality (from 16% to 20%) would result in a decline in the Suwannee River Gulf sturgeon population. Population trends were consistent for both modeling procedures and were similar to those in published reports. Although this population is currently expanding, care should be taken to protect adult fish from any fishing or bycatch mortality. Given the particular attributes of Gulf sturgeon (such as late sexual maturation, the fact that few mature females spawn each year, and high early life mortality), managers should be patient and willing to monitor populations for extended periods of time (∼20 years) to detect changes in the adult population. [ABSTRACT FROM AUTHOR]

Black crappies Pomoxis nigromaculatus exhibit highly variable survival to adulthood because of their varying larval and juvenile abundance, growth, and mortality during early life. We examined how growth and mortality changed with hatch date, prey density, and water temperature for 7-d cohorts of juvenile black crappies in Lake Wauberg, Florida (a 150-ha hypereutrophic natural lake) during spring and summer 1998. Fish were collected once per week from March through June and twice per month during July and August by means of an otter trawl. Based on daily otolith rings, hatching occurred over a 12-week period (1 March−18 May). The mean daily growth rate (DGR) was positively related to water temperature, which increased over the hatching season. Common prey taxa included calanoid copepods, Daphnia and Bosmina spp., and cyclopoid copepods. The total density of these taxa did not differ significantly among collection dates. Mean hatching date shifted from mid-March for fish collected in mid-April to early April for fish collected in late May. Early-hatched fish had lower DGRs (0.72 mm/d, compared with 0.76 mm/d for fish hatched in midseason and 0.82 mm/d for those hatched late in the season), higher mean daily instantaneous mortality rates (0.25, compared with 0.09 for the other two groups), and lower survival to the end of the first summer. As a result, the 1998 year-class of black crappies in Lake Wauberg was probably dominated by middle- and late-hatched individuals by the end of the first summer. [ABSTRACT FROM AUTHOR]

The article discusses a study on effects of free-air carbon dioxide (CO2) enrichment (FACE) on an underground processes of forest of loblolly pine, or Pinus taeda. It states that the co2 level was increased above ambient levels using a FACE apparatus, and mentions role of CO2 in plant production. It cites that the CO2 in soil increase after the first year of FACE treatment, and notes changes associated with the plant like microbial biomass.