Crappie Pomoxis Research Articles

Status, trends, and population demographics of selected sportfish species in the La Grange Reach of the Illinois River

Abstract
 Sportfish species, specifically Yellow Bass Morone mississippiensis, White Bass Morone chrysops, Largemouth Bass Micropterus salmoides, Bluegill Lepomis macrochirus, Black Crappie Pomoxis nigromaculatus, and White Crappie P. annularis, often drive economically valuable fisheries in large river systems, including the Upper Mississippi River System (UMRS). Within the Illinois River, part of the UMRS, these species are routinely sampled by an ongoing long-term fisheries monitoring program. Through this program, we investigated long-term trends (1993-2017) in catch rates and relative weights and quantified demographic rates from 2012-2016. We found all six species, with the exception of Yellow Bass, to have declining catch rates with this decline being most stark in larger, older fishes. Population demographics for Yellow Bass, White Bass, Bluegill, and Black Crappie suggest populations are dominated by younger individuals, with only Black Crappie regularly living to age 3 and older, which may be driving population declines. There are many environmental stressors acting on the Illinois River that could be contributing to the lack of older and larger fishes, including, but not limited to, navigation efforts, altered hydrology, pollution, sedimentation, lack of overwintering habitat, and introduction of invasive species. Results of this study demonstrate that additional research to understand mechanisms driving reduced abundance and stunted age structure are needed to identify effective management actions that would benefit populations of recreationally valuable sportfish species.

Potential Effects of Age, Population, and Latitude on Precision of Scale and Otolith Age Estimates of White Crappie in Minnesota

Abstract We calculated between-reader precision of ages estimated with scales and whole otoliths (sagittae) of White Crappie Pomoxis annularis for 10 Minnesota populations, and determined effects of population and mean age on precision. For all samples combined, two experienced readers counted the same number of annuli on 91% of the scales and 92% of the whole otoliths. Mean coefficients of variation equaled 1.8% between scale readers and 3.0% between whole otolith readers. We detected no systematic age-bias between readers of each structure. Agreement between scale readers differed among populations, ranging from 67 to 100% among populations (median = 89%), but agreement also decreased with increasing scale age in six of these populations. Agreement between readers of whole otoliths was unaffected by increasing age of White Crappie, but agreement ranged from 39 to 100% among populations. When compared with other studies, latitude had no influence on precision of whole otolith ages because precision in the Minnesota populations differed little from precision reported for populations in Kentucky and Mississippi. Latitude could be affecting precision in scale age estimates because precision was usually better for the Minnesota populations than for populations in Oklahoma, Kentucky, and Mississippi; however, differences in viewing methods and reader competencies could also explain geographical differences.

Standard Assessments Reveal Context‐Dependent Responses of Crappie Populations to a Length‐Based Regulation in Ohio Reservoirs

AbstractFisheries managers implement minimum length limits (MLLs) to improve the size structure of populations of crappie Pomoxis spp. throughout Midwestern and southeastern U.S. reservoirs. The success of these regulations has been mixed, with several implementations resulting in undesirable outcomes, including slow growth and stunting of crappies, and ultimately regulation removal. Consequently, it is unclear whether and where MLLs should be used to improve crappie size structure. Beginning in 2003, Ohio instituted a statewide standard sampling protocol to monitor reservoir crappie populations, and between 2003 and 2010 a 229‐mm MLL was implemented at over 40 reservoirs throughout the state. Using these spatially and temporally extensive crappie population data, we sought to (1) test for the response of crappie population adult abundance, growth, and size structure to the MLL, (2) test whether reservoir surface area and/or productivity mediated this response, and (3) model fisheries outcomes at different reservoir sizes and productivities to predict where application of a MLL would be most appropriate. Using linear mixed‐effects models and an information theoretic approach, we found that crappie population abundances generally increased, whereas growth decreased in small, unproductive reservoirs but increased in large, productive reservoirs. Overall, the MLL failed to produce increases in size structure, except in large reservoirs. Yield‐per‐recruit models predicted a decrease in angler yield in response to a 229‐mm MLL in small reservoirs, whereas in large, productive reservoirs this regulation was predicted to increase angler yield. Consequently, the MLL could improve crappie fisheries in reservoirs larger than 1,000 ha with high productivity (total phosphorus concentrations > 50 μg/L) but could be counterproductive in small, unproductive reservoirs. Finally, our approach highlights the benefits of standard sampling as we were able to integrate data across years and reservoirs to make comparisons on a statewide scale.

Feeding Regime Has Little Impact on Weight Loss of Hybrid Crappies Pomoxis spp. and Redear Sunfish at a Low (Winter) Water Temperature when Fed a Noncommercial Diet of Blood Worms

AbstractWinter mortality is a problem for fish producers in temperate regions of the USA, including Arkansas. Hybrid crappies (Black Crappie Pomoxis nigromaculatus × White Crappie P. annularis) and Redear Sunfish Lepomis microlophus are popular among recreational anglers. Methods of winter feeding vary widely among existing commercial farms. The impact of different winter feeding regimes on performance of hybrid crappies and Redear Sunfish was evaluated in temperature‐controlled aquarium systems. Juvenile hybrid crappies and Redear Sunfish were cultured at approximately 9°C to mimic winter conditions. Three feeding regimes were implemented (3 tanks/regime) in which an ad libitum ration of blood worms was administered twice per week, once per week, or once per month. After 13 weeks of culture, there were no observed differences in weight loss, survival, specific growth rate, or final individual weight for either hybrid crappies or Redear Sunfish. Hybrid crappies lost 27–29% of their initial body weight, while Redear Sunfish lost more than 30% of their initial body weight. Fatty acid composition of both species differed significantly among feeding treatments, showing a decline in saturated fatty acids from initial levels and increases in or static levels of highly unsaturated fatty acids. Results suggest that feeding regime has little effect on weight gain in hybrid crappies and Redear Sunfish when fed at a colder water temperature.

Consistently High Trophic Overlap between Invasive White Perch and Native Black Crappies in Southeastern Reservoirs

AbstractThe detrimental impacts of invasive species often occur through deleterious trophic interactions (e.g., competition) with native species. However, the potential for competitive interactions between species may vary among systems, among seasons, or throughout the species’ ontogeny, requiring a thorough examination of trophic niches to determine whether overlap exists and to elucidate the likelihood of competition. The Black Crappie Pomoxis nigromaculatus is a popular game fish species across the United States, but recent invasions of White Perch Morone americana, which exploit a similar trophic niche, into southern reservoirs represent a major concern for the continued sustainability of Black Crappie fisheries. We examined the trophic niches of these species throughout their ontogeny in two North Carolina reservoirs during 2009 and 2010 using a combination of diet content and stable isotope analyses. Extensive and significant similarities in diet composition and isotopic niche overlap existed between Black Crappies and White Perch throughout their ontogeny and across seasons in both systems. Overlap was particularly high between smaller (<200‐mm), invertivorous Black Crappies and all sizes of White Perch. This overlap suggests that if invertebrate resources become limited, competition during the juvenile stage could reduce growth rates and survival of young Black Crappies. By evaluating variation in the trophic niches of each species among seasons, body sizes, and reservoirs, we conclude that the potential for competitive interactions between White Perch and Black Crappie is high in southern reservoirs. Management options to either reduce White Perch abundance or prevent their spread to novel habitats may be necessary to sustain native and supplemented Black Crappie populations that are potentially vulnerable to White Perch invasions.

Survey of Intersex (Testicular Oocytes) in Black Crappie Collected from the Illinois River Waterway

Abstract Researchers have documented intersex (testicular oocytes) in male fishes in many species worldwide and prevalence of the condition is strongly related to exposure to endocrine-disrupting compounds in aquatic ecosystems. There is no available knowledge about the incidence of intersex in Black Crappie Pomoxis nigromaculatus, an important North American sport fish. The objective of this survey was to investigate the prevalence and distribution of the intersex condition in Black Crappie collected from portions of the Illinois River waterway. We collected and examined 83 Black Crappie. We observed testicular oocytes in 22 individuals (27% intersex), representing the first documentation of intersex condition in wild Black Crappie. The number of oocytes that we observed in intersex Black Crappie ranged from 1 to 67. We documented intersex in individuals collected from all habitats, but there were no significant differences in the prevalence of the condition (Kruskal–Wallis P = 0.56) or the number of oocytes present (P = 0.25) in intersex males from the different habitats. Permutational multivariate analysis of variance indicated that morphometric parameters varied significantly among locations (P = 0.0001), but did not vary significantly between intersex and normal males. We have little information about the current distribution of endocrine-disrupting compounds in the specific regions where we collected Black Crappie for our study. However, we believe our study represents a valuable effort to detect the condition in an important sport fish and lays a foundation for future research.

Fish Community Responses to Submerged Aquatic Vegetation in Maumee Bay, Western Lake Erie

AbstractSubmerged aquatic vegetation (SAV) in clearwater systems simultaneously provides habitat for invertebrate prey and acts as refugia for small fishes. Many fishes in Lake Erie rely on shallow, heavily vegetated bays as spawning grounds and the loss or absence of which is known to reduce recruitment in other systems. The Maumee River and Maumee Bay, which once had abundant macrophyte beds, have experienced a decline of SAV and an increase in suspended solids (turbidity) over the last century due to numerous causes. To compare fish communities in open‐water (turbid) and in SAV (clearer water) habitats in this region, which is designated by the U.S. Environmental Protection Agency as an Area of Concern, and to indicate community changes that could occur with expansion of SAV habitat, we sampled a 300‐ha sector of northern Maumee Bay that contained both habitats. Using towed neuston nets through patches of each habitat, we determined that areas of SAV contained more species and a different species complex (based on the Jaccard index and the wetland fish index), than did the open‐water habitat (averaging 8.6 versus 5 species per net trawl). The SAV habitat was dominated by centrarchids, namely Largemouth Bass Micropterus salmoides, Bluegill Lepomis macrochirus, and Black Crappie Pomoxis nigromaculatus. Open‐water habitat was dominated by Spottail Shiner Notropis hudsonius, Gizzard Shad Dorosoma cepedianum, and White Perch Morone americana, an invasive species. These results indicate that restoration efforts aimed at decreasing turbidity and increasing the distribution of SAV could cause substantive shifts in the fish community and address important metrics for assessing the beneficial use impairments in this Area of Concern.

Assessing the Utility of Otolith Chemistry for Management of Six Freshwater Fishes from a River–Reservoir System

AbstractFloodplain habitats often function as spawning, rearing, foraging, and refuge environments for riverine fishes. Although floodplain habitats are important for fish production and recruitment, their natal contributions may vary by species, a topic that has not been thoroughly investigated in large floodplain rivers. We evaluated the natal contributions of floodplain habitats to populations of six socioeconomically important sport fishes in Lake Sharpe, South Dakota, using otolith chemistry. Water samples and age‐0 and adult fishes were sampled from five habitat types (canal, embayment, main channel, stilling basin, tributary). Age‐0 fishes were classified to known natal habitats with 83% mean accuracy based on otolith Ba:Ca and Sr:Ca signatures, with 89% mean accuracy for Bluegill Lepomis macrochirus (89%), crappies Pomoxis spp. (88%), and Largemouth Bass Micropterus salmoides (91%). Floodplain habitats had substantial natal contributions to Bluegill (50%) and crappie (35%) populations. Despite spanning only 0.8% of Lake Sharpe by surface area, a specific floodplain habitat (Hipple Lake) contributed 15% of Largemouth Bass to the Lake Sharpe population—19 times greater than expected under a linear contribution–area relationship. Floodplain habitats had smaller natal contributions (0–5%) for reservoir‐oriented species such as Smallmouth Bass M. dolomieu and White Bass Morone chrysops than for centrarchids and Yellow Perch Perca flavescens. Given that floodplain habitats in Lake Sharpe, particularly Hipple Lake, are disproportionately important for sport fish populations relative to their size, maintaining river–floodplain connectivity is crucial for effective fisheries management. Otolith chemistry is a tool for sport fish management in Lake Sharpe as it reveals habitat‐specific natal contributions of diverse species and can be used to prioritize areas for floodplain protection and rehabilitation, harvest regulations, stock enhancement, and other fisheries management activities.

Assessing the Influence of Tilapia on Sport Fish Species in North Carolina Reservoirs

AbstractRedbelly Tilapia Tilapia zilli and Blue Tilapia Oreochromus aureus are indigenous to Africa and the Middle East, but now occur throughout the southeastern United States. It is fairly well understood that foraging flexibility and wide salinity, oxygen, and temperature tolerances have led to general invasion success for most tilapia species. Conflicting empirical information about the influence of tilapia on native sport fish species, however, leaves natural resource managers unable to anticipate and prevent further introductions and potential associated risks to native sport fishes. This investigation focused on two North Carolina reservoirs with tilapia populations: Hyco Lake, a large reservoir in northcentral North Carolina and Lake Julian, a small impoundment in western North Carolina. These reservoirs receive heated effluent from power generation, which is assumed to provide winter refuge for tilapia at a time when temperatures would otherwise lead to mortality. We assessed relative abundances of the tilapias and native sport species (Bluegill Lepomis macrochirus, black basses Micropterus spp., and Black Crappie Pomoxis nigromaculatus) in these systems and examined their trophic interactions via diet and stable isotope analyses in both lakes. In Hyco Lake we assessed potential spatial interactions and influences on relative abundance using a priori candidate models and model selection via Akaike's information criterion (AIC). These analyses indicated little evidence of tilapias influencing the relative abundances of the sport species in Hyco Lake. In both lakes, however, we did find substantial diet overlap between the tilapias and Bluegill along with isotopic niche overlap between Blue Tilapia and Bluegill in Lake Julian and Redbelly Tilapia and Bluegill in Hyco Lake. Due to the omnivorous and flexible diet of all three species these interactions were not surprising, but the ultimate influence on Bluegill growth and size structure is unknown. Overall, our results suggest that tilapia are exploiting trophic niches that are not used by the sport fishes of interest in these two very different reservoir systems and that their direct impact on sport species is not substantial.

Species‐ and habitat‐specific otolith chemistry patterns inform riverine fisheries management

AbstractGeology and hydrology are drivers of water chemistry and thus important considerations for fish otolith chemistry research. However, other factors such as species and habitat identity may have predictive ability, enabling selection of appropriate elemental signatures prior to costly, perhaps unnecessary water/age‐0 fish sampling. The goal of this study was to develop a predictive methodology for using species and habitat identity to design efficient otolith chemistry studies. Duplicate water samples and age‐0 fish were collected from 61 sites in 4 Missouri River reservoirs for walleye Sander vitreus and one impoundment (Lake Sharpe, South Dakota) for other fishes (bluegill Lepomis macrochirus, black crappie Pomoxis nigromaculatus, gizzard shad Dorosoma cepedianum, largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, white bass Morone chrysops, white crappie P. annularis, and yellow perch Perca flavescens). Water chemistry (barium:calcium [Ba:Ca], strontium:calcium [Sr:Ca]) was temporally stable, spatially variable, and highly correlated with otolith chemistry for all species except yellow perch. Classification accuracies based on bivariate Ba:Ca and Sr:Ca signatures were high (84% across species) yet varied between floodplain and main‐channel habitats in a species‐specific manner. Thus, to maximize the reliability of otolith chemistry, researchers can use species classifications presented herein to inform habitat selection (e.g., study reservoir‐oriented species such as white bass in main‐channel environments) and habitat‐based classifications to inform species selection (e.g., focus floodplain studies on littoral species such as largemouth bass). Overall, species and habitat identity are important considerations for efficient, effective otolith chemistry studies that inform and advance fisheries and aquatic resource management.

Description of a New Species of Caecincola (Trematoda: Cryptogonimidae) with a Key to the Species

Abstract Caecincola aubergina n. sp. is described from white crappie (Pomoxis annularis) from B. A. Steinhagen Reservoir in southeastern Texas, U.S.A. Members of C. aubergina n. sp. have an elongate body (5.5–8.8:1 length:width ratio), a multilobed ovary, large vitelline follicles primarily in the hindbody but extending into the forebody, and an oral sucker that is wider than long. The elongate form of the new specimens distinguishes them from all other species in the genus except Caecincola longiscens and Caecincola cookorum. In the former species, vitelline follicles are confined to the hindbody; in the latter species, the body is peanut-shaped and the vitelline follicles are almost entirely in the forebody. This is the eighth species of Caecincola, and a dichotomous key to the species is presented as well.

Outbreak of Cleidodiscus in juvenile black crappies (Pomoxis nigromaculatus) and bath treatment with praziquantel.

Outbreak of Cleidodiscus in juvenile black crappies (Pomoxis nigromaculatus) and bath treatment with praziquantel.

Fillet Weight and Fillet Yield: New Metrics for the Management of Panfish and Other Consumption‐Oriented Recreational Fisheries

AbstractProposals for regulations to improve panfish size structure often lack angler support, in part because of a perceived loss of panfish harvest. We propose that fillet weight and fillet yield, the percentage of the body weight available as fillets, are useful metrics for exploring regulation options and potential outcomes. We determined fillet weight and fillet yield for 321 Bluegill Lepomis macrochirus, 139 Black Crappie Pomoxis nigromaculatus, and 137 Yellow Perch Perca flavescens and developed equations to predict fillet weight from total length. Mean fillet yield was 29.5% for Bluegills, 28.6% for Black Crappies, and 33.1% for Yellow Perch. We used Bluegill size increases associated with a reduction in daily bag limits from 25 fish to 10 fish in seven Wisconsin lakes and then estimated fillet weights to compare the potential total weight of Bluegill fillets available to anglers under both a 10‐ and a 25‐fish daily bag limit. We projected that many anglers might obtain a greater weight of Bluegill fillets per fishing trip under a 10‐fish bag limit. We conclude that for consumption‐oriented fisheries, fillet weight and fillet yield have value in demonstrating how more restrictive harvest regulations may sometimes lead to a greater weight of fillets for most anglers.Received April 19, 2016; accepted February 10, 2017 Published online April 11, 2017

A New Species ofCaecincola(Trematoda: Cryptogonimidae) from White Crappie (Pomoxis annularis) in Southeastern Texas, U.S.A.

ABSTRACT: Caecincola cookorum n. sp. is described from the intestine of white crappie (Pomoxis annularis) collected from B. A. Steinhagen Reservoir in Tyler County, Texas, U.S.A. Worms of the new species possess ceca that extend past the posterior testis, whereas members of the other species in the genus (Caecincola autumnae, Caecincola latostoma, Caecincola longiscens, Caecincola parvulus, and Caecincola wakullata) have ceca that terminate before the end of the posterior testis. This is the second species of Caecincola described from white crappie from rivers draining into the Gulf of Mexico (C. longiscens from Mississippi being the other), and it is possible that a large fraction of the species-level diversity in this genus remains to be discovered.

White Crappie Tank Culture and Out‐of‐Season Spawning

AbstractWhile extensive crappie culture has been practiced for decades, limited knowledge of crappie aquaculture methods has hampered the production potential of White Crappie Pomoxis annularis to a small time frame during the natural spawning season, which occurs only once annually. Out‐of‐season spawning of White Crappie could greatly enhance annual production potential. Therefore, White Crappie out‐of‐season spawning experiments were conducted from November to February in recirculating tank systems. After 2 weeks of simulated winter (10°C, 8 h light), photoperiod and temperature were increased to spring (22°C, 16 h light) conditions over 3 weeks (1°C and 30 min increase every 2 d) and 6 weeks (1°C and 30 min increase every 4 d). Fish were injected with gonadotropin‐releasing hormone analog (GnRHa; 100% priming dose and 100% resolving dose, 24 and 48 h later) and strip‐spawned upon ovulation. The 3‐week treatment (11 females : 10 males) induced 1 female to spawn with 11% fertilization rate. The 6‐week treatment (12 females : 10 males) induced 2 females to spawn with fertilization rates of 31.5% and 79.2%. Gonads of unspawned females were sampled at 96 h after the resolving dose to assess reproductive maturity. Gonadosomatic index (GSI) and egg diameter (ED) from unspawned females (3‐week GSI [mean ± SE] = 0.02 ± 0.01, ED = 0.71 ± 0.22; 6‐week GSI = 0.03 ± 0.02, ED = 0.72 ± 0.10) were compared with wild females sampled during December (winter; GSI = 0.02 ± 0.01; ED = 0.53 ± 0.07) and April (spring; GSI = 0.04 ± 0.01; ED = 0.90 ± 0.12). No difference between 6‐week GSI and spring GSI was detected; however, ED was smaller for 3‐ and 6‐week treatments when compared with spring ED. Therefore, out‐of‐season spawning of White Crappies, using recirculating tank systems and hormone‐induced spawning, is possible, but a longer seasonal shift regime is needed to enhance spawning success.

Length Selectivity and Size‐Bias Correction for the North American Standard Gill Net

AbstractGill nets are inherently size selective, but selectivity curves can correct this bias. We sampled eight reservoirs with the North American standard gill net to develop a large length‐specific data set for six species: Channel Catfish Ictalurus punctatus, hybrid Striped Bass (White Bass Morone chrysops × Striped Bass M. saxatilis), saugeye (Sauger Sander canadensis × Walleye S. vitreus), Walleye, White Bass, and White Crappie Pomoxis annularis. We then used the SELECT (share each lengthclass's catch total) method to find the best‐fit selectivity model to adjust the gill‐net catch for contact selectivity. To determine the magnitude of these selectivity corrections, we compared adjusted and unadjusted length frequencies and size indices for each species at each reservoir. The bimodal model was the best fit selectivity model for all species. When selectivity‐adjusted length‐frequency data were compared with the original data, one‐third of hybrid Striped Bass length frequencies and two‐thirds of White Bass length frequencies were significantly different (unadjusted distributions underestimated smaller length classes). Roughly one‐third of the proportional size distributions (PSDs) from all species analyzed showed meaningful changes (≥5 PSD units) after selectivity adjustments were made (unadjusted PSDs were too large). By correcting for contact selectivity the data are improved, and at times the adjustments can be large enough to alter management decisions. Therefore, we recommend that selectivity adjustments should become a part of routine data analysis for the design of the North American standardized gill net as this will improve data for fisheries management.Received September 1, 2015; accepted December 21, 2015 Published online May 16, 2016

Seventy‐Year Retrospective on Size‐Structure Changes in the Recreational Fisheries of Wisconsin

To identify past successes and future opportunities for improved fisheries management in Wisconsin, we synthesized size‐structure information on 19 gamefish species from 1944 to 2012, incorporating data on more than 2 million measured individuals. Since the 1940s, mean and mean maximum sizes of five “gamefish” species (Lake Sturgeon Acipenser fulvescens, Largemouth Bass Micropterus salmoides, Smallmouth Bass M. dolomieu, Northern Pike Esox lucius, and Sauger Sander canadensis) have stayed fairly stable, and one (Muskellunge E. masquinongy) initially dropped and then rebounded—most likely as a product of increased catch‐and‐release fishing and restrictive harvest regulations. In contrast, four “panfish” species (i.e., Bluegill Lepomis macrochirus, Green L. cyanellus, Yellow Perch Perca flavescens, and Black Crappie Pomoxis nigromaculatus), which have not received the same conservation management attention, have experienced substantial and sustained erosions in size over the same period. Regulations for many species and species complexes have been cyclical over time, illustrating the challenge of consistently managing fisheries. Our long‐term retrospective analysis was effective at identifying new opportunities for improved fisheries management in Wisconsin (i.e., panfish management). We therefore encourage other big data retrospective approaches within and across regions to identify past successes and future opportunities in other fisheries management programs.

Histopathologic evaluation of postmortem autolytic changes in bluegill (Lepomis macrohirus) and crappie (Pomoxis anularis) at varied time intervals and storage temperatures.

Information is lacking on preserving fish carcasses to minimize postmortem autolysis artifacts when a necropsy cannot be performed immediately. The purpose of this study was to qualitatively identify and score histologic postmortem changes in two species of freshwater fish (bluegill—Lepomis macrochirus; crappie—Pomoxis annularis), at varied time intervals and storage temperatures, to assess the histologic quality of collected samples. A pooled sample of 36 mix sex individuals of healthy bluegill and crappie were euthanized, stored either at room temperature, refrigerated at 4 °C, or frozen at −20 °C, and then necropsied at 0, 4, 24, and 48 h intervals. Histologic specimens were evaluated by light microscopy. Data showed that immediate harvesting of fresh samples provides the best quality and refrigeration would be the preferred method of storage if sample collection had to be delayed for up to 24 h. When sample collection must be delayed more than 24 h, the preferred method of storage to minimize autolysis artifacts is freezing if evaluation of the gastrointestinal tract is most important, or refrigeration if gill histology is most important. The gill arch, intestinal tract, followed by the liver and kidney were the most sensitive organs to autolysis.

Using Hierarchical Bayesian Multispecies Mixture Models to Estimate Tandem Hoop‐net‐Based Habitat Associations and Detection Probabilities of Fishes in Reservoirs

AbstractSpecies distribution models are useful tools to evaluate habitat relationships of fishes. We used hierarchical Bayesian multispecies mixture models to evaluate the relationships of both detection and abundance with habitat of reservoir fishes caught using tandem hoop nets. A total of 7,212 fish from 12 species were captured, and the majority of the catch was composed of Channel Catfish Ictalurus punctatus (46%), Bluegill Lepomis macrochirus (25%), and White Crappie Pomoxis annularis (14%). Detection estimates ranged from 8% to 69%, and modeling results suggested that fishes were primarily influenced by reservoir size and context, water clarity and temperature, and land‐use types. Species were differentially abundant within and among habitat types, and some fishes were found to be more abundant in turbid, less impacted (e.g., by urbanization and agriculture) reservoirs with longer shoreline lengths; whereas, other species were found more often in clear, nutrient‐rich impoundments that had generally shorter shoreline length and were surrounded by a higher percentage of agricultural land. Our results demonstrated that habitat and reservoir characteristics may differentially benefit species and assemblage structure. This study provides a useful framework for evaluating capture efficiency for not only hoop nets but other gear types used to sample fishes in reservoirs.Received October 14, 2014; accepted December 23, 2015 Published online April 11, 2016

Escapement of Fishes from Modified Fyke Nets with Differing Throat Configurations

AbstractWe performed a field experiment in five eastern South Dakota lakes to investigate fish escapement differences between modified fyke nets with two common throat configurations (restricted and unrestricted). Nets with restricted and unrestricted throats were deployed in pairs for 24 h on similar habitat. Captured fish were measured for TL and were given day‐specific marks. The paired nets were redeployed, and marked fish were randomly assigned to be stocked into the restricted or unrestricted net for 24 h; stocking densities (stratified into low, medium, and high) were species specific. Marked fish that were retained after 24 h were used to quantify escapement, whereas newly captured fish were used to estimate differences in mean CPUE and size structure. Mean CPUE of Black Bullheads Ameiurus melas, Black Crappies Pomoxis nigromaculatus, and Bluegills Lepomis macrochirus approximately doubled when restricted nets were used. Mean TL of Black Crappies was 31 mm greater (95% confidence interval [CI] = 6–57 mm greater) and mean TL of Bluegills was 21 mm greater (95% CI = 8–35 mm greater) in restricted nets than in unrestricted nets. Escapement from restricted nets was 4.4% for Black Crappies and 10.3% for Bluegills, whereas escapement from unrestricted nets was 71.7% for Black Crappies and 58.4% for Bluegills. We urge researchers to consider the influence of varying fyke‐net throat configurations on calculated population metrics, and we recommend inclusion of the restricted throat feature in gear specifications for North American standard modified fyke nets.Received April 6, 2015; accepted October 14, 2015