Blue Catfish Ictalurus Furcatus Research Articles

Development of an Effective Cryopreservation Protocol for Blue Catfish Oogonia

AbstractLong‐term storage of oogonia and germ‐line stem cells provides an alternative to the limitations associated with cryopreserving eggs of important fish species. These cell types are less vulnerable to the stresses of freezing. Cryopreservation has enormous potential for aquaculture advancement, but protocols must be developed for each species and cell type since its success hinges on various input factors. Blue Catfish Ictalurus furcatus were selected as the test species in this study because of the need to improve fry production of Blue Catfish ♂ × Channel Catfish I. punctatus ♀ hybrids, which can be facilitated by storing oogonia in gene banks. Our objective was to develop a freezing protocol for oogonia of this species. We tested different permeating and nonpermeating cryoprotectants, concentrations of these agents, and freezing rates. We proved that all three factors influenced postthaw recovery of oogonia. Of the permeating cryoprotectants, 1.0 M dimethyl sulfoxide resulted in the most live cells with the highest viability percentages, and adding 0.2 M lactose with 10% egg yolk further improved the results. There were also specific interactions in which the effects of concentration and freezing rate varied among the cryoprotectant treatments. The most effective freezing rate was −1.0°C/min, and cell viability was reduced at −2.5°C/min and −5.0°C/min. From these results, we propose adding 1.0 M dimethyl sulfoxide with 0.2 M lactose and 10% egg yolk to cryomedia and freezing it at a rate of −1.0°C/min. By developing a cryopreservation protocol for a commonly cultured catfish, this work may guide the development of protocols for other species of interest.

Specialized Feeding Patterns and Marine Resource Use by Nonnative Catfishes in a Coastal River Ecosystem Revealed by Dietary and Stable Isotopic Analyses

AbstractTwo large predatory catfishes, the Flathead CatfishPylodictis olivarisand Blue CatfishIctalurus furcatus, have been introduced into multiple U.S. Atlantic slope drainages in recent decades, with concomitant reductions in native fish abundance and changes in faunal community composition. Here, we report on a study of the trophic ecology of sympatric Flathead Catfish and Blue Catfish in the lower Cape Fear River, North Carolina, to estimate trophic positions and identify possible impacts on marine and estuarine prey resources. We applied both dietary and stable isotope analysis to quantify species‐specific foraging patterns, as well as the extent of variation among tributaries, seasonal periods, and ontogeny. Both catfish species displayed limited dietary breadth and specialized feeding patterns focused on prey resources within a restricted range of trophic levels. Dietary overlap between Blue Catfish and Flathead Catfish was low, and the species were separated by more than one trophic position. Flathead Catfish relied heavily on fish prey throughout ontogeny, with macroinvertebrates (crustaceans) as a consistent secondary prey resource, and showed increased reliance on potential anadromous prey resources at the largest sizes. Blue Catfish diets were dominated by the invasive Asian clamCorbicula fluminea, with contributions from fish prey only increasing for the largest individuals. Catfish trophic ecology varied among tributaries, and to a greater extent for Flathead Catfish, in terms of both the fish fauna eaten and the relative contribution of different invertebrate prey. Isotopic signatures for Flathead Catfish aligned with stomach contents to indicate a greater contribution of marine prey resources, including anadromous fishes, in the main‐stem Cape Fear River compared with the Black and Northeast Cape Fear rivers. Our findings indicate that the predatory impacts of catfishes introduced to coastal river ecosystems will differ considerably between catfish species and may also vary within systems across fine spatial scales.

Comparative Mortality of Juvenile Channel and Hybrid Catfish Exposed to Bolbophorus damnificus Cercariae

AbstractThe trematode Bolbophorus damnificus (Digenea: Bolbophoridae) has caused significant economic losses since the late 1990s, with deleterious effects on production efficiency in farm‐raised catfish. Previous work has demonstrated that even mild outbreaks, which may go unnoticed by producers, can result in over 60% reduction in net economic returns. Although transmission rates in Channel Catfish Ictalurus punctatus and hybrid catfish (Channel Catfish × Blue Catfish Ictalurus furcatus) are similar in controlled studies, anecdotal industry reports imply that the impacts of B. damnificus on hybrid catfish are less severe. In this study, mortality in juvenile Channel and hybrid catfish exposed to B. damnificus was evaluated in two discrete, replicated infectivity challenges. Mortality curves in Channel and hybrid catfish were consistent with trends previously established for B. damnificus in Channel Catfish, although in both challenges cumulative mortality was significantly lower in hybrids. All exposed fish presented clinical signs consistent with B. damnificus infection—namely lethargy, exophthalmia, distended abdomens, and metacercariae grossly visible below the skin. No mortality occurred and no parasites were observed in control fish. The biological and economic implications of these findings on catfish production are unknown but suggest that hybrid catfish are less susceptible to the deleterious effects and reduced productivity elicited by B. damnificus in Channel Catfish.

Exploring Legacy Data Sets to Infer Spatial and Temporal Trends in the Ictalurid Assemblage of an Atlantic Slope River

AbstractThe Cape Fear River basin is located along the southeastern Atlantic Slope and is the largest river basin located within North Carolina. Historically, the ictalurid assemblage was characterized by five species of bullhead Ameiurus spp. and three species of madtom Noturus spp. Channel Catfish Ictalurus punctatus were introduced in the early 20th century, followed by Flathead Catfish Pylodictis olivaris in 1965 and Blue Catfish Ictalurus furcatus in 1966. Long‐term analysis of the ictalurid assemblage has been confounded by disparate data sets in both electronic and historical paper‐based document archives. The goal of this study was to merge contemporary and legacy agency data sets to elucidate spatial and temporal trends in the ictalurid assemblage of the Cape Fear River basin. Rotenone surveys conducted in the 1960s documented abundant madtoms and White Catfish Ameiurus catus throughout the basin. Native species comprised the majority of the ictalurid assemblage through the early 1990s. Since 1990, Blue and Flathead catfish have been the dominant species observed. The largest native ictalurid, the White Catfish, has not been collected since 2008. Nonmetric multidimensional scaling suggests that native ictalurids were more prevalent in small tributaries with increasing distance from the initial adult Flathead Catfish stocking location. Despite the widespread distribution and abundance of nonnative ictalurids, several native species are still found in small tributaries in upstream watersheds. The North Carolina Catfish Management Plan prioritizes the conservation of native ictalurids in the state's Atlantic Slope rivers; however, some species may already be extirpated.

Age Determination of Hybrid Catfish and Channel Catfish from Commercial Catfish Farms

AbstractProcessing plants prefer live catfish ranging from 0.45 to 1.81 kg as they are readily processed and sold to established markets. Catfish routinely escape harvest, become “big fish” (>1.81 kg) in one to two production cycles, receive a reduced price, and can reduce farm profitability. This study determined age structure of Channel Catfish Ictalurus punctatus and hybrid catfish (male Blue Catfish Ictalurus furcatus × female Channel Catfish) that were “big fish” from commercial catfish ponds and estimated growth rates to determine when fish reach these sizes. In summer 2018, 153 Channel Catfish and 134 hybrid catfish were collected from commercial catfish farms in western Alabama and aged using lapilli otoliths. Hybrid catfish had faster growth than Channel Catfish and were larger at every age‐class sampled during the study. Premium‐sized fish were comprised solely of age‐2 and age‐3 fish for both species, but 72% of age‐2 Channel Catfish were premium size, compared to only 40% of age‐2 hybrid catfish. On average, Channel Catfish and hybrid catfish reached “big fish” size in 2.5 and 1.5 years, respectively. Thus, farmers should try to harvest most fish within these time frames or renovate ponds to mitigate these issues.

Size‐Specific Exploitation of Flathead Catfish and Blue Catfish by Recreational and Commercial Fishers in the Missouri and Mississippi Rivers, Missouri

AbstractSize‐selective harvest in a fishery is a growing point of contention among different catfish anglers. In response to these concerns, size‐specific exploitation rates of Flathead Catfish Pylodictus olivaris and Blue Catfish Ictalurus furcatus by recreational anglers and commercial fishers were quantified. Eight study reaches were randomly selected on the Missouri River (4 reaches; recreational harvest only) and the Mississippi River (4 reaches; recreational and commercial fishing allowed). Fish were captured by electrofishing in 2015 and 2016 and were tagged with Carlin dangler reward tags. A total of 3,370 tags were distributed among 12 size‐groups starting at 381 mm TL, of which 609 tags were reported during the study period. High‐reward (US$150) tags were used to estimate nonreporting of standard ($25) tags. Reporting rates varied by reach and constituency group and ranged from 19% to 100%. Overall exploitation rates of Flathead Catfish were comparable to those in other studies (0.10–0.19) but were highly variable among sizes and among reaches. Commercial fishers did not harvest any fish smaller than 584 mm, and they tended to be more size selective than recreational anglers. Exploitation of Blue Catfish by recreational anglers was highest for 840–890‐mm fish (0.34–0.43) in the Missouri River and for 891–1,015‐mm fish (0.24–0.28) in the Mississippi River. Commercial harvest of Blue Catfish was not significantly different among size‐groups and was much lower than recreational harvest. These data indicated that recreational anglers and commercial fishers were often selective for mid‐ to larger‐size fish rather than for small sizes. Understanding the levels and potential range of size‐specific exploitation of catfish in larger rivers will aid managers when setting appropriate regulations and balancing the competing objectives of these fisheries.

Susceptibility of Channel Catfish (Ictalurus punctatus), Blue Catfish (Ictalurus furcatus), and Their Commercially Cultured Hybrid to Metazoan Parasite Infection in Earthen Pond Aquaculture

We herein document the metazoan parasite component communities of channel catfish (Ictalurus punctatus), blue catfish (Ictalurus furcatus), and their commercially cultured hybrid (female I. punctatus × male I. furcatus) communally stocked as parasite-free fingerlings into each of 3 experimental earthen ponds (each pond harbored channel catfish, blue catfish, and hybrid catfish). The fundamental objective of this work was to test the hypothesis that hybrid catfish exhibit less susceptibility to infection by metazoan parasites than do their parental species. Fingerlings of each catfish species from each pond were parasitologically examined monthly for 1 yr. A total of 112 channel catfish, 74 blue catfish, and 209 hybrid catfish were necropsied; collectively resulting in the detection of 14 metazoan parasite species. Channel catfish had the most diverse component community (12 species: 3 myxozoans, 2 monogenoids, 3 cestodes, 1 nematode, 1 unionid, and 2 copepods) followed by hybrid catfish (11 species: 3 myxozoans, 2 monogenoids, 2 cestodes, 1 nematode, 1 unionid, and 2 copepods) and blue catfish (6 species: 1 myxozoan, 2 monogenoids, 2 cestodes, and 1 copepod). These results do not support the assertion that hybrid catfish are demonstrably more resistant to parasitic infection than either parental species. New host–parasite records herein comprise Corallotaenia intermedia (Fritts, 1959) Freze, 1965, and Corallotaenia parafimbriata (Befus and Freeman, 1973) Scholz, de Chambrier, Mariaux, and Kucha, 2011 for channel catfish; Henneguya sp., C. parafimbriata, and Neoergasilus japonicus (Harada, 1930) Yin, 1956 for blue catfish; and Henneguya adiposaMinchew, 1977, Henneguya bulbosusRosser, Griffin, Quiniou, Khoo, and Pote, 2014, Ligictaluridus mirabilis (Mueller, 1937) Beverley-Burton, 1985, Ligictaluridus pricei (Mueller, 1936) Beverley-Burton, 1984, Essexiella fimbriata (Essex, 1928) Scholz, de Chambrier, Mariaux, and Kucha, 2011, C. parafimbriata, Spiroxys sp., Pyganodon sp., N. japonicus, and Achtheres sp. for hybrid catfish. To our knowledge, this is the most extensive parasitological study of this particular hybrid catfish, or any hybrid catfish, published to date.

A Bayesian multistate approach to evaluate movements of an invasive freshwater estuarine-opportunist

Coastal rivers and estuaries provide habitat and migratory corridors for freshwater estuarine-opportunists. We evaluated movement patterns of 61 blue catfish (Ictalurus furcatus) in the tidal York and Rappahannock rivers in Virginia, USA with acoustic telemetry from July 2015 to June 2016. To evaluate river-specific movements, we utilized a multistate Cormack–Jolly–Seber (CJS) model within a Bayesian framework to estimate probabilities of detection and transition (movement) among established salinity zones (i.e., tidal-fresh (0‰–0.5‰), oligohaline (>0.5‰–5‰), mesohaline (>5‰–18‰)). We considered flow as an environmental covariate. Despite high site fidelity in tidal-fresh zones, some individuals displayed movements into oligohaline and mesohaline habitats indicative of partial migration. Once downstream movement occurred, the probability of staying in the new salinity zone was higher than the probability of movements to other salinity zones. In the Rappahannock River only, movement upstream from mesohaline habitats was associated with below average flow. As flow increased, the probability of remaining in oligohaline and mesohaline zones increased. Our study shows blue catfish can move into downstream areas of tidal rivers with elevated salinities and that increased freshwater flow may allow them to remain in these habitats for extended durations.

Effects of Chase Boat Use, Electrofishing Duration, and Water Velocity on Sample Efficiency and Size Structure of Blue Catfish

AbstractChase boats are used to assist in the capture of Blue Catfish Ictalurus furcatus because they often surface relatively far from the electrofishing boat (electrofisher) when incapacitated by low‐frequency, pulsed DC. We conducted this study to determine how chase boat use affects size‐related and capture efficiency metrics of Blue Catfish, and we concurrently examined possible confounding effects of sample duration and velocity on these metrics. We used DC at 15 pulses/s in 5‐ or 10‐min runs during four trials that were stratified by reservoir zone, season, and macrohabitat over a 2‐year period in Pool 10 of the Arkansas River (Lake Dardanelle, Arkansas). We captured 4,330 fish in 96 samples and analyzed the catch data by size‐group (all fish; >199, >299, and >509 mm). We compared samples of fish captured by an electrofisher alone with those collected by the electrofisher in combination with a chase boat (chase+). The electrofisher‐only protocol captured a greater proportion of fish less than 300 mm compared to the chase+ protocol, but length‐frequency distributions of larger‐size fish did not differ. Overall catch was greater for the chase+ protocol, with the difference generally increasing by size‐group except for the largest fish. Catch efficiency was greater for 5‐ versus 10‐min samples for both protocols, with the relative difference increasing as fish size increased. Calculated values of the proportional size distribution of quality‐size fish were sufficiently similar among all combinations of protocol and duration for management purposes. The practical implication is that an electrofisher‐only protocol can be used to collect representative samples of Blue Catfish, but the use of a chase boat increases the average catch per boat.

Virulence and immunogenicity of blue catfish alloherpesvirus in channel, blue and blue×channel hybrid catfish.

Blue catfish alloherpesvirus (BCAHV) is a novel virus isolated from the blue catfish (Ictalurus furcatus). To date, the ultrastructure, virulence and immunogenicity of BCAHV have not been reported. Given the importance of blue catfish in producing channel ♀ (I. punctatus)×♂ blue (I.furcatus) catfish hybrids and the increasing demand for hybrid catfish in the US catfish industry, the susceptibility of blue, channel and hybrid catfish to BCAHV was assessed. Further, the cross-protective potential of BCAHV against Ictalurid herpesvirus 1 (IcHV1) was investigated in channel and hybrid catfish that survive BCAHV exposure. Neutralization assays revealed BCAHV is refractive (neutralization index [NI]=0) to anti-IcHV1 monoclonal antibody Mab 95, compared to IcHV1 (NI=1.8). Exposure of blue catfish fingerling to 1.3×105 TCID50 /L BCAHV produced cumulative mortality of 51.67±0.70% and pathologic changes similar to those of channel catfish virus disease. No mortality was observed in channel or hybrid catfish. Twenty-eight days post-challenge, surviving channel and hybrid catfish were exposed to 9.4×104 TCID50 /L IcHV1 (LC50 dose), resulting in 100% relative per cent survival compared to naïve cohorts. These data provide baseline information for BCAHV and lay the groundwork for future studies. Data also identify BCAHV as a potential vaccine candidate against IcHV1. Based on host range and immunogenicity evaluations, in addition to genome sequence data from previous studies, BCAHV should be given consideration as a new species of Ictalurivirus.

Efficacy and Temporal Capture Patterns of Bank Poles in the Kansas River: A Novel Sampling Tool for Catfish

AbstractSetlines and trotlines are useful tools for sampling catfish populations. These gears offer an alternative to sampling in habitats or conditions that are unsuitable for traditional sampling gears, and they may be capable of sampling a different subset of the population. However, little is known about their efficacy as catfish sampling gear. We developed a standardized method for deploying setlines in the form of bank poles and assessed the catch rate, species composition, and efficacy of bank poles in the Kansas River, Kansas. We also used Lindgren‐Pitman hook timers to investigate temporal patterns of capture, retention rates, and optimal soak duration. Bank poles (n = 897) were equipped with 6/0 circle hooks baited with Silver Carp Hypophthalmichthys molitrix cut bait and were deployed overnight during the summers of 2018 and 2019. Bank poles captured a total of seven fish species, with 97% of the species composition being catfishes (n = 258; mean TL = 688 ± 182.7 mm; range = 392–1,310 mm). Blue Catfish Ictalurus furcatus (45%) was the most commonly captured species, followed by Channel Catfish I. punctatus (37%) and Flathead Catfish Pylodictis olivaris (15%). The success rate for hooking and landing fish with bank poles was 29%. There was no difference between total catch rates from standard bank poles and those from bank poles equipped with hook timers. Higher catch rates were observed early in the set time for Channel and Flathead catfish, whereas a relatively steady catch rate was observed for Blue Catfish. Overall, 46% of catfish were caught within 3 h of gear deployment and 72% were caught within 5 h. We recommend adopting shortened soak durations (about 5 h) to prevent bait loss and to optimize fish retention. Our study provides an alternative sampling approach to increase the catch of large individuals and offers insight into the catch dynamics and interactions of passive angling gears.

A Review of Marking and Tagging Methods for Blue Catfish, Channel Catfish, and Flathead Catfish

AbstractCatfishes (Ictaluridae) are among North America’s most important ichthyofauna for human consumption and recreation. As such, research on Blue Catfish Ictalurus furcatus, Channel Catfish I. punctatus, and Flathead Catfish Pylodictis olivaris has been abundant in historic and contemporary literature. A common technique for studying catfish involves marking or tagging fish to understand behavior, sampling efficiency, and population dynamics. Marking and tagging methods used in these studies may be divided into eight primary types, including fin clips, strap tags, anchor tags, transbody tags, injectable tags, skin alterations, origin markers, and telemetry. Each of these methods is appropriate for specific objectives and characterized by varying retention rates and data resolution (i.e., batch or individual identification) that warrant consideration when designing projects. For example, fin clips may be most appropriate as a short‐term mark requiring batch identification (e.g., stocking evaluation), whereas telemetry might be most appropriate as a long‐term tag requiring individual identification (e.g., habitat selection). This review summarizes marking and tagging methods used for evaluation of Blue, Channel, and Flathead catfish and synthesizes results using examples from previously conducted catfish research. Further discussion is included on information gaps, emerging trends, and guidance for scientists planning and conducting studies that require marking of catfish.

Reproductive Characteristics Differ in Two Invasive Populations of Blue Catfish

AbstractThe management of invasive Blue Catfish Ictalurus furcatus in Chesapeake Bay tributaries is hindered by the lack of information on its reproductive biology, which is a key component of population models used to forecast abundance. We quantified and compared the reproductive traits of female Blue Catfish from two populations from the tidal reaches of the James and York River subestuaries during 2015–2017. In these systems, Blue Catfish matured between the ages of 6 and 10 years and spawned between May and July, with larger fish spawning earlier in the season. During spawning events, Blue Catfish produced 2,613–68,356 eggs, with larger and older fish producing more eggs. Fish in the more densely populated James River matured at a marginally older age but a significantly smaller size than fish in the York River, but James River fish allocated more energy to reproduction. Fish in the James River also had greater mean values of the gonadosomatic index, relative fecundity, egg organic content, and proportion of organic content in the eggs. Relative fecundity of Blue Catfish decreased with fish size, contrary to observations in most other fishes. Based on the observed variability in reproductive traits and the size dependence of relative fecundity, we recommend incorporation of population‐specific reproductive rates into stock assessment models for invasive Blue Catfish.

Environmental Variation and Habitat Use Affect Blue Catfish Low‐Frequency Electrofishing Catch Rates

AbstractThe Blue Catfish Ictalurus furcatus is a popular sport fish in its native range and a prolific invasive species in its nonnative range. Low‐frequency electrofishing (LFE) is effective for sampling Blue Catfish, and development of standardized LFE protocols for sampling Blue Catfish is critical for monitoring and management of their populations. However, standardized sampling for Blue Catfish can be difficult because their habitat use is variable among seasons and habitats, and LFE is affected by a suite of abiotic factors. To quantify this variation, our objectives were to determine how Blue Catfish LFE catch (1) differs during spring and summer sampling seasons, (2) is affected by environmental variables, and (3) relates to their habitat use. To do so, we conducted a telemetry study and systematic random LFE sampling in Lake Dardanelle, Arkansas, in the spring and summer of 2016. We compared the numbers, capture rates, and size structure (proportional size distribution index of quality‐size fish) of telemetry‐located and LFE‐captured Blue Catfish in distinct habitats and found that habitat use was heterogeneous but capture rates were proportional to habitat use. Blue Catfish catch increased with conductivity and decreased with flow velocity; catch also differed among habitat types, among reservoir zones, and between seasons (spring/summer). Understanding how spatiotemporal differences in habitat use contextualize the effects of LFE catch will improve sampling protocols for Blue Catfish.

Evaluating Growth Rates of Two Newly Introduced Populations of Blue Catfish in Kansas

Blue Catfish Ictalurus furcatus have been introduced into many of Kansas reservoirs since 1972. They ranked sixth in terms of favorite fish to catch and target among licensed Kansas anglers in 2013 despite limited management. Blue Catfish were sampled and aged from two reservoirs located on the northern and western periphery of their current distribution.Fish were sampled using experimental gill nets, low frequency electrofishing, and float lines. Ages were assigned to a subset of captured fish by a panel of three independent readers examining a thin section cut from the articulating surface of a pectoral spine. Rapid growth was observed in Lovewell Reservoir with Blue Catfish reaching 659-mm by age 6. Growth of Blue Catfish was slower in Wilson Reservoir (552-mm by age 6) but comparable to other populations in the United States. Recruitment of stocked fish was variable but more consistent in Lovewell Reservoir. Year classes established by stockings that contained larger individuals at greater densities were more prevalent in both populations. These results demonstrate inconsistent recruitment patterns of Blue Catfish population development when stocked in large reservoirs.

Using Creel Data to Evaluate Blue and Channel Catfish Aggregate Harvest Regulations for Texas Reservoirs

AbstractThe Texas Parks and Wildlife Department’s strategic management plan for catfishes (Ictaluridae) called for the development of alternative harvest regulations for Blue Catfish Ictalurus furcatus and Channel Catfish I. punctatus. Angler harvest of these species in most Texas reservoirs has been regulated using a 305‐mm minimum length limit (MLL) and a 25‐fish aggregate daily bag limit (DBL) since 1995. Using existing creel data collected in 2003–2018 at 86 Texas reservoirs managed under this statewide harvest regulation, we examined Blue and Channel Catfish harvest size structure and composition, percent release of legally harvestable‐size fish, and harvest density (number and biomass). Additionally, for reservoirs having long‐term creel data, we evaluated temporal change in percent release of legally harvestable‐size fish and harvest size structure, and we estimated the impact of alternative harvest regulations by using a theoretical harvest reduction (THR) model. Channel Catfish were the predominant species harvested (>75% of harvest) in 63% of the reservoirs. Harvest size structures of Blue and Channel catfish differed, but the difference in percent harvest of fish smaller than 406 mm was negligible (52% and 48%, respectively). Percent release of legally harvestable‐size fish (≥305 mm) was low at most reservoirs (median = 13%). Total number of catfish harvested per hectare per quarter (HHQ) ranged widely (0.0–11.3) but was less than 1.0 at 58% of reservoirs. Harvest size structure was truncated over time coincident with a high harvest level (HHQ > 3.0) at two of four reservoirs with long‐term data, suggesting growth overfishing. The THR model revealed that increases in MLL resulted in variable harvest reductions among reservoirs and that removal of the 305‐mm MLL could increase harvest by 6–39%. Additionally, we found that length‐graduated DBLs would have a negligible impact on reducing the harvest of larger fish. We suggest that MLLs are not necessary for most Texas catfish fisheries and that a 356‐mm MLL may be appropriate for high‐harvest fisheries.

Estimates of Food Consumption Rates for Invasive Blue Catfish

AbstractAs a prolific invasive species, Blue Catfish Ictalurus furcatus threaten native organisms in numerous estuarine and tidal freshwaters along the Atlantic coast of the United States. However, no published estimates of consumption rates are available for Blue Catfish in the scientific literature. This information is critical for development of bioenergetics models or estimation of population‐level impacts on native species. Using a combination of field and laboratory studies, we provide the first estimates of daily ration, maximum daily ration, and consumption to biomass ratios for Blue Catfish populations. Ad libitum feeding trials conducted in our laboratory reveal that maximum daily ration in Blue Catfish varies by prey type, temperature, and fish size, with maximal feeding occurring in medium‐sized Blue Catfish (500–600 mm total length) and at temperatures ≥15°C. Furthermore, estimates of daily ration were higher for fish prey (Gizzard Shad Dorosoma cepedianum) than for crustacean prey (blue crab Callinectes sapidus). Diel feeding chronologies based on field‐collected diet samples from 1,226 Blue Catfish demonstrated river‐specific variability in daily ration and maximum daily ration. Blue Catfish daily ration ranged between 2.27% and 5.22% bodyweight per 24 h, while maximum daily ration ranges between 8.56% and 9.37% bodyweight per 24 h. Estimates of consumption to biomass ratios varied by river and Blue Catfish size groupings but range between 2.42 and 3.39, which is similar to other benthic omnivores. This research will inform the assessment of predatory impacts of invasive Blue Catfish in the Chesapeake Bay and beyond as it will enable researchers to estimate predatory impacts through the coupling of population models, food habit information, and consumption rate information (current study).

Evaluation of Recently Implemented Harvest Regulations in a Data‐Limited Catfish Fishery with Bayesian Estimation

AbstractIn 2015, the Illinois Department of Natural Resources changed size and harvest limits for catfishes (Blue Catfish Ictalurus furcatus, Flathead Catfish Pylodictis olivaris, and Channel Catfish I. punctatus) in the lower Ohio River to match those of neighboring states. The new regulations imposed a daily limit of one 88.9‐cm (35‐in) or larger Blue or Flathead Catfish per fisher, one 71.1‐cm (28‐in) or larger Channel Catfish per fisher, and a 33.0‐cm (13‐in) minimum length limit for all species, with no harvest restrictions between these limit lengths (permissive slot). When these management regulations were implemented, potential efficacy was unknown. The goal of this study was to evaluate the potential effects of these regulations using the limited data for baseline demographic parameters. Bayesian modeling was used to estimate growth and mortality because of the ability to estimate derived functions of parameters and associated uncertainty (as credible intervals). Yield‐per‐recruit (YPR) modeling was used to estimate and evaluate the fishing mortality rates (F) that would induce growth overfishing (FMAX) and the yield at FMAX (YPRMAX) for three management scenarios: no harvest restrictions (former regulation), a 33.0‐cm minimum length limit, and the enacted permissive slot limits. Model results suggested that catfish stocks are unlikely to benefit from current regulations given the near‐complete overlap of YPRMAX credible intervals for all estimable scenarios and the small significant differences (1–3%) based on FMAX between the most permissive and most restrictive scenarios. Despite the existence of significant differences in FMAX, they are likely biologically irrelevant based on the life histories of these species. Although modeling results suggested that the implemented harvest regulations will not likely affect catfish population demographics or fishery yield in the lower Ohio River, a post hoc evaluation examining the accuracy of these predictions is needed and would improve the accuracy and precision of parameter estimates.

High-throughput sequencing outperforms traditional morphological methods in Blue Catfish diet analysis and reveals novel insights into diet ecology.

Blue Catfish Ictalurus furcatus are an invasive, yet economically important species in the Chesapeake Bay. However, their impact on the trophic ecology of this system is not well understood. In order to provide in‐depth analysis of predation by Blue Catfish, we identified prey items using high‐throughput DNA sequencing (HTS) of entire gastrointestinal tracts from 134 samples using two genetic markers, mitochondrial cytochrome c oxidase I (COI) and the nuclear 18S ribosomal RNA gene. We compared our HTS results to a more traditional “hybrid” approach that coupled morphological identification with DNA barcoding. The hybrid study was conducted on additional Blue Catfish samples (n = 617 stomachs) collected from the same location and season in the previous year. Taxonomic representation with HTS vastly surpassed that achieved with the hybrid methodology in Blue Catfish. Significantly, our HTS study identified several instances of at‐risk and invasive species consumption not identified using the hybrid method, supporting the hypothesis that previous studies using morphological methods may greatly underestimate consumption of critical species. Finally, we report the novel finding that Blue Catfish diet diversity inversely correlates to daily flow rates, perhaps due to higher mobility and prey‐seeking behaviors exhibited during lower flow.

Invasive Blue Catfish in the Chesapeake Bay Region: A Case Study of Competing Management Objectives

AbstractFreshwater fishes have been introduced outside their native range to establish recreational fisheries, but management conflicts arise when such introductions also result in potentially harmful effects on native species. In this case study, we focus on Blue Catfish Ictalurus furcatus, which were introduced in the Chesapeake Bay region and are now considered invasive. In many tidal tributaries, Blue Catfish have increased dramatically in abundance, expanded into high‐salinity habitats (up to 21.8 psu), and negatively affected native species, prompting calls for the development of an effective management plan. However, management of this conflict species is complicated by multiple competing objectives, including control of population size, maintenance of trophy fisheries, and expansion of commercial fisheries for Blue Catfish. Seven management recommendations were advanced by the Invasive Catfishes Work Group to control the spread and limit the ecological impacts of Blue Catfish on native species. We highlight opportunities for addressing these complex management issues and guide our suggestions using results from research on invasive Blue Catfish ecology and population dynamics, as well as management of invasive species in general. A formal approach, such as structured decision analysis, is required to resolve conflicts among user groups and to address the wicked problem of Blue Catfish in the Chesapeake Bay region.