Channel Catfish Populations Research Articles

Explaining Channel Catfish Population Characteristics in Ohio Reservoirs

AbstractNorth American fisheries management agencies commit considerable resources to managing reservoir fisheries for Channel Catfish Ictalurus punctatus, which often includes stocking. However, Channel Catfish population characteristics often vary greatly among reservoirs, resulting in variable and unpredictable fishery quality. We sampled Channel Catfish populations in 44 Ohio reservoirs with tandem, baited hoop nets to understand relationships among population characteristics (density, as CPUE from hoop nets; growth, as mean length at age 7; mortality, as total annual mortality from catch‐curve analysis; and size structure, as proportional size distribution), stocking, and the relationships between these characteristics and reservoir size (as surface area), predator density (as Largemouth Bass Micropterus salmoides electrofishing CPUE), and productivity (as chlorophyll‐a concentration). We used multiple linear regression and an information theoretic approach to select the most parsimonious models for explaining observed variation in Channel Catfish density, growth, mortality, and size structure. We found that population density varied greatly among our study reservoirs, and none of our models sufficiently explained variation in density. Reservoir size and the interaction between reservoir size and population density explained the most variation in Channel Catfish growth, but productivity was also important. Small reservoirs (≤101 ha) had low to moderate densities and growth was uniformly slow; however, in larger reservoirs, lower densities resulted in faster growth. Growth increased as productivity increased. Total annual mortality was uniformly low (<0.26) but increased with density. Faster growth led to populations with larger size structures. These outcomes show that the largest Ohio reservoirs (≥406 ha) are the most suitable for supporting populations with fast growth and large size structures. Dense populations (CPUE > 50 Channel Catfish/net set) resulted in slower growth, greater mortality, and poor size structure. Future research to understand natural recruitment in reservoir Channel Catfish populations could be important for explaining variation in density.

Indexing Reservoir Channel Catfish Population Density and Size Structure with Tandem, Baited Hoop Nets

AbstractFisheries managers efficiently sample reservoir Channel Catfish Ictalurus punctatus populations with tandem, baited hoop nets. However, catchability (the fraction of a fish stock caught with a defined unit of effort) of Channel Catfish with this gear and the size selectivity of this gear are not fully known. Furthermore, scientists have not identified a standard sampling period that maximizes catches while minimizing variation in catchability. Here, we estimated Channel Catfish population density (number/ha) and catchability with tandem, baited hoop nets using mark–recapture methods in three Ohio reservoirs during May–July 2016–2018. We tested for differences in catchability (1) among reservoirs; (2) among 50‐mm length categories; and (3) by week. We then tested CPUE as an index of density by simulating the sampling of populations with different densities based on observed variation in catchability and estimating the statistical power to detect density differences. We found that total catchability differed among study reservoirs, among length categories, and among sampling events but did not consistently change during the May–July sampling period. Catchability of 50‐mm length categories did not differ among reservoirs. The greatest catchability was observed for 400–649‐mm Channel Catfish. Our power analysis showed that we could detect a large (>2:1 effect sizes) difference in density with 80% power by using 20 or more sample sites. Furthermore, our length‐category‐specific catchability estimates provide information to reduce bias in size structure, growth, and mortality estimates derived from Channel Catfish samples collected with tandem, baited hoop nets. We encourage further development, validation, and application of tandem, baited hoop nets to better understand differences in reservoir Channel Catfish densities and size structures.

Comparing Channel Catfish Populations in the Fragmented Minnesota River

AbstractChannel Catfish Ictalurus punctatus provide important fisheries in lotic systems throughout much of North America, but few studies have evaluated the influence of dams and habitat fragmentation on their populations. The Minnesota River is an important recreational catfish fishery in Minnesota that is fragmented by Granite Falls Dam, located 395 km upstream from the confluence with the Mississippi River. Granite Falls Dam is a significant barrier to upstream fish passage; consequently, the upstream fish community is less diverse than the downstream community and habitat availability differs between reaches. For this study, hoop‐net assessments conducted by the Minnesota Department of Natural Resources during 2014–2017 were used to compare Channel Catfish catch rates, size structure, growth, and annual survival between the upstream and downstream reaches. Hoop‐net catch rates upstream (mean ± SE = 45.1 ± 5.2 fish/net‐night) were significantly greater by an order of magnitude compared to catch rates downstream (3.9 ± 0.4 fish/net‐night). Size structure of Channel Catfish also significantly differed between reaches: the percentage of stock‐length (≥280‐mm) fish that were preferred length or larger (≥610 mm) was 28.4% downstream compared to 5.8% upstream. Annual survival estimates and growth indices were generally similar between reaches, but there was evidence of greater longevity downstream, where the oldest aged fish were 24 years compared to 19 years upstream. This study demonstrates population differences that may be influenced and exacerbated by habitat fragmentation and provides support for considering each population individually when making future management decisions.

Gear specific catch rates and size structure of channel catfish in the Upper Mississippi River

AbstractChannel catfish are important to the Mississippi River (i.e., ecologically, commercially, and recreationally). The dynamic rate functions (recruitment, growth, and mortality) of the population are important to proper management. However, different gears can produce varying estimates of these vital rates (e.g., size selectivity or age selectivity). We evaluated the effectiveness of three commonly used gear types for sampling channel catfish. Sampling was completed following United States Army Corps of Engineers' Long‐Term Resource Monitoring (LTRM) element sampling protocol; pulsed direct current daytime electrofishing, baited 37 mm hoop nets (large hoop net), baited 18 mm hoop nets (small hoop net), and a tandem hoop net set that included one large and one small hoop net. A total of 65,222 channel catfish were collected from 1993 to 2017. Channel catfish catch rates were lowest using daytime electrofishing and large hoop nets, while tandem hoop nets and small hoop nets had higher catch per unit effort (CPUE). Furthermore, tandem hoop nets collected a broader size distribution of channel catfish in comparison to daytime electrofishing, large hoop nets, and small hoop nets. As such, we recommend that tandem hoop nets should be used to evaluate channel catfish populations in the Upper Mississippi River as well as other riverine systems.

Population Dynamics and Simulated Effects of Length‐Based Trophy Regulations for Flathead and Channel Catfish in the Lower James River, South Dakota

AbstractCatfish are popular with anglers fishing southeastern South Dakota rivers, and a group of anglers has expressed concern about the perceived overharvest of trophy‐size catfish. However, existing data are insufficient for determining whether Flathead CatfishPylodictis olivarisand Channel CatfishIctalurus punctatusare being overharvested. Our objective was to determine the population dynamics of Flathead and Channel catfish and model potential outcomes of length‐based trophy regulations (one fish and no fish harvested over 610 mm) in the lower James River, South Dakota. Multiple gears were used to collect Flathead Catfish (low‐frequency electrofishing and trotlines) and Channel Catfish (baited hoop nets and low‐frequency electrofishing) during 2018, and samples were augmented with angler‐caught catfish collected from three angling tournaments. Pectoral spines were removed from a subsample of fish for age estimation; 305‐mm and larger fish received a Carlin dangler tag with a reward value of US$0, $10, or $100. Growth rates were slow to moderate for Flathead Catfish and moderate for Channel Catfish. Trophy‐size Flathead Catfish (TL ≥ 1,020 mm) were sampled, but few of the collected Channel Catfish exceeded preferred length (TL ≥ 610 mm). Total annual mortality was estimated at 25.7% for Flathead Catfish and 25.2% for Channel Catfish. Exploitation estimated from angler reward tag returns was less than 1% for each species. Yield‐per‐recruit models indicated that a regulation specifying one fish over 610 mm would slightly reduce yield for both species but would only increase the number of memorable‐length Flathead Catfish (860 mm) and Channel Catfish (710 mm) by less than 1%. A no‐harvest regulation would substantially reduce yield of Flathead Catfish and would increase the number of memorable‐length Flathead Catfish by approximately 2% and Channel Catfish by less than 1%. Information obtained during this study suggests that current Flathead and Channel Catfish populations have limited trophy potential and that length‐based trophy regulations would have limited impact on the abundance of large catfish in the lower James River.

Quantifying Consumption of Native Fishes by Nonnative Channel Catfish in a Desert River

AbstractThe establishment of nonnative predators can have devastating consequences for native fish communities, but predation rates are often difficult to quantify due to spatial and temporal variation in predator foraging behavior. Predation by Channel Catfish Ictalurus punctatus throughout the Colorado River basin potentially threatens the recovery of native fishes. Because Channel Catfish are highly opportunistic feeders, an understanding of how piscivory by this species impacts prey populations should help to guide management in invaded systems. We used laboratory observations to model temperature‐dependent stomach evacuation rates and combined those estimates with field‐collected diet data to derive annual consumption across a 152‐km reach of the San Juan River (New Mexico, Colorado, and Utah). In the field, stomach fullness increased with water temperature while the probability of observing fish prey in the diet increased with TL of Channel Catfish and water turbidity. Based on estimates of daily ration, diet composition, and Channel Catfish population demographics, we estimated the San Juan River population’s fish consumption to be 4.9 kg·ha−1·year−1 (95% CI = 4.0–6.1 kg·ha−1·year−1) in 2018 and 2.3 kg·ha−1·year−1 (95% CI = 1.8–2.8 kg·ha−1·year−1) in 2019. Native fishes accounted for 54% of the fish biomass consumed, which included two incidents of endangered Colorado Pikeminnow Ptychocheilus lucius consumption. Although these estimates should help managers to assess the predatory threat of Channel Catfish, additional information, such as the efficacy of nonnative control and prey population compensatory responses, will likely be necessary to develop robust management strategies aimed at reducing the predatory impacts of this nonnative species on native fish assemblages.

An orally delivered, live‐attenuated Edwardsiella ictaluri vaccine efficiently protects channel catfish fingerlings against multiple Edwardsiella ictaluri field isolates

AbstractThe commercial channel catfish (Ictalurus punctatus) industry is adversely impacted by enteric septicemia of catfish (ESC), caused by the Gram‐negative enteric rod Edwardsiella ictaluri. In efforts to develop more effective management strategies, the use of a live‐attenuated E. ictaluri isolate as an oral vaccine was investigated. The utility and broad application of a vaccine is dependent on the protection offered against multiple field isolates. Immunization trials, followed by bacterial challenge with archived virulent E. ictaluri isolates from the catfish farming region of the southeastern United States, were conducted over a 3‐year period. These isolates were archived from 1993 to 2016 and included representatives from nonvaccinated and vaccinated populations of diseased channel catfish in Mississippi, an isolate from nonvaccinated hybrid catfish raised in Mississippi, and an isolate from nonvaccinated channel catfish from Alabama. Molecular characterization of the isolates revealed a high degree of genetic similarity evidenced by repetitive sequence‐mediated polymerase chain reaction (rep‐PCR) fingerprinting and virulence gene amplification, suggesting that the population of E. ictaluri within catfish aquaculture in Mississippi and Alabama has been genetically stable over time. Plasmid profiling revealed the existence of at least four distinct plasmids among field isolates. Nevertheless, the E. ictaluri vaccine protected fish against all isolates, irrespective of heterogeneous or homogeneous plasmid profiles. In addition, plasmid profiles were supported by antimicrobial sensitivity testing, indicating that the E. ictaluri vaccine strain does not carry natural or plasmid‐mediated multidrug resistance to the three antibiotics approved for use in U.S. food fish aquaculture. Challenge data from this study argue against the need for multivalent E. ictaluri vaccines to account for presumed antigenic or genetic variation among wild‐type E. ictaluri isolates as the vaccine was effective against all archived isolates.

Ecosystem-specific growth responses to climate pattern by a temperate freshwater fish

Abstract Somatic growth patterns among animal populations are maintained through complex processes that vary among ecosystems. Changes in growth patterns may be concomitant with changes in climate; however, understanding how growth will manifest among ecosystems is limited. Information embedded within fish hard-parts (i.e., otoliths, spines, vertebrae) can account for variation in growth patterns resulting from changing climate conditions. Channel catfish Ictalurus punctatus is a freshwater fish species widely distributed across North America with limited information regarding climate influences on growth and differences in climate-growth relations among ecological systems. We assessed growth (total length) response to changing climate conditions for channel catfish among three waterbody types—pit lakes, irrigation and power-generation reservoirs, and flood-control reservoirs in Nebraska, USA. We used linear mixed-effect models and an information theoretic approach to assess the relative strengths among competing hypotheses. The most supported linear mixed-effect model of channel catfish growth was a function of fish age and an interaction between waterbody type and growing-degree-day (GDD). A positive trend existed in GDD from 1990 through 2008 whereby the predicted increase in GDD among waterbody types ranged from 182 GDD to 189 GDD. The predicted change in channel catfish growth resulting from increased GDD ranged from 1% to 39% among waterbody types. Channel catfish population rate functions, thus, may not respond similarly to climate conditions across ecosystem types. Changes in climate variables may contribute to system-specific responses in population dynamics for channel catfish as well as other similar freshwater species. The establishment of relations between climate and growth variables for a freshwater generalist with a plastic diet and broad temperature tolerance serves as an indication of the breadth of responses possible for freshwater fishes under global changes in climate conditions.

Effects of Handling Methods of Gravid Channel Catfish on Cortisol Response and Reproductive Performance to Produce Hybrid Catfish Fry

AbstractThere is a need to optimize production protocols to improve the efficiency of embryo production in commercial catfish hatcheries for hybrid catfish (female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus). The present study compared two methods of handling broodfish from a Channel Catfish population while they are being transferred from pond to hatchery. Sexually mature females (average weight = 3.9 kg/fish) were seined and transported in a hauling truck to the hatchery prior to being injected with hormones. The fish that were placed in soft mesh bags (confined) were compared with fish that were allowed to swim freely (nonconfined) in the hauling truck and raceway in the hatchery. The fish were bled at seining (0 h), after transport to the hatchery (1 h), and while in the raceway at 4 and 24 h, respectively, and plasma levels of cortisol were measured. The broodfish that were suspended in soft mesh bags were monitored for ovulation and strip‐spawned to determined their relative fecundity (eggs/kg of body weight) and fry/kg body weight. The results showed that cortisol levels were high after seining in both groups. The cortisol concentrations were significantly lower (P < 0.05) at 1 and 4 h in the nonconfined than in the confined group. By 24 h, the cortisol levels had decreased in both of the treatment groups. The average relative fecundity (9,617 versus 8,576) and the number of fry/kg body weight (3,039 versus 2,710) were significantly higher (P < 0.05) for the nonconfined fish than for the confined fish. Minimizing handling and confining stress of gravid Channel Catfish after seining during transport to the hatchery and holding them in hatchery tanks for 4 h prior to hormone injection appears to be beneficial to the hatchery production of hybrid catfish fry.

Effects of florfenicol feeding on diversity and composition of the intestinal microbiota of channel catfish ( Ictalurus punctatus )

Intestinal microbiota contributes health of living organisms. Florfenicol is an approved antimicrobial (AM) prescribed for several bacterial fish diseases. The present study investigated the extent to which florfenicol modulates intestinal microbial populations of channel catfish (Ictalurus punctatus). Florfenicol was administered orally to catfish at a standard therapeutic dose (10–15 mg/kg of body weight for 10 days), and the intestinal contents were collected and the 16S rRNA was subjected to Illumina sequencing. Alpha diversity analysis indicated that florfenicol significantly decreased microbiota richness and diversity. Beta diversity reflected a clear separation had occurred between the florfenicol-fed and control groups. Results indicated a significant increase in the abundance of phylum Proteobacteria (98.97% vs. 79.35% of the population) and decrease in phyla Firmicutes and Bacteroidetes (0.72% and 0.29% vs. 18.04% and 2.53%, respectively) in the florfenicol-fed fish in comparison with the control fish. At the genus level, unclassified Enterobacteriaceae and Escherichia populations increased in the florfenicol group. In contrast, Plesiomonas, Aeromonas, Lactococcus, Clostridium sensu stricto, Romboutsia, Klebsiella, Turicibacter and Lactobacillus decreased in florfenicol-fed fish in comparison with the control fish, indicating that intestinal microbiota of catfish was substantially modulated by florfenicol administration. Knowledge of changes in gut microbiota during medicated feed administration is important to improve fish performance and disease management and could enable the development of alternative therapeutic strategies.

Genetic Diversity and Structure of Channel Catfish from Continental Waters of Mexico

AbstractMexico is the native site of 10 species of the genus Ictalurus, among which the Channel Catfish I. punctatus has great presence in worldwide aquaculture. Wild populations of catfish not only constitute a biological resource but have a great potential for aquaculture. Recently, this species was classified as an invasive organism by the Mexican government. The aim of this study was to determine the structure and genetic diversity of Channel Catfish belonging to native and introduced freshwater populations within Mexico. Using 11 DNA microsatellite loci, we analyzed 292 fish sampled from four rivers and five reservoirs. Observed heterozygosity values ranged between 0.66 and 0.80. The genetic distance analysis showed low to high differentiation among populations (overall genetic differentiation index FST = 0.14). Bayesian coancestry analysis identified two ancestral groups. A single management population on central Tamaulipas can be suggested. The findings of the present study provide the basis for future characterization of productive traits of Mexican Channel Catfish populations in order to use the species as a breeding source for aquaculture. The lower Rio Grande population is one of the most ancient and ecologically relevant Channel Catfish populations in Mexico, and this study identifies it as the most vulnerable. Free‐living populations of Channel Catfish, although they have been heedlessly spread, constitute a valuable natural resource that deserves our best effort to preserve.

Development of genomic predictions for harvest and carcass weight in channel catfish

BackgroundCatfish farming is the largest segment of US aquaculture and research is ongoing to improve production efficiency, including genetic selection programs to improve economically important traits. The objectives of this study were to investigate the use of genomic selection to improve breeding value accuracy and to identify major single nucleotide polymorphisms (SNPs) associated with harvest weight and residual carcass weight in a channel catfish population. Phenotypes were available for harvest weight (n = 27,160) and residual carcass weight (n = 6020), and 36,365 pedigree records were available. After quality control, genotypes for 54,837 SNPs were available for 2911 fish. Estimated breeding values (EBV) were obtained with traditional pedigree-based best linear unbiased prediction (BLUP) and genomic (G)EBV were estimated with single-step genomic BLUP (ssGBLUP). EBV and GEBV prediction accuracies were evaluated using different validation strategies. The ability to predict future performance was calculated as the correlation between EBV or GEBV and adjusted phenotypes.ResultsCompared to the pedigree BLUP, ssGBLUP increased predictive ability up to 28% and 36% for harvest weight and residual carcass weight, respectively; and GEBV were superior to EBV for all validation strategies tested. Breeding value inflation was assessed as the regression coefficient of adjusted phenotypes on breeding values, and the results indicated that genomic information reduced breeding value inflation. Genome-wide association studies based on windows of 20 adjacent SNPs indicated that both harvest weight and residual carcass weight have a polygenic architecture with no major SNPs (the largest SNPs explained 0.96 and 1.19% of the additive genetic variation for harvest weight and residual carcass weight respectively).ConclusionsGenomic evaluation improves the ability to predict future performance relative to traditional BLUP and will allow more accurate identification of genetically superior individuals within catfish families.

Genome-wide association analysis of intra-specific QTL associated with the resistance for enteric septicemia of catfish.

Disease resistance is one of the most important traits for aquaculture industry. For catfish industry, enteric septicemia of catfish (ESC), caused by the bacterial pathogen Edwardsiella ictaluri, is the most severe disease, causing enormous economic losses every year. In this study, we used three channel catfish families with 900 individuals (300 fish per family) and the 690K catfish SNP array, and conducted a genome-wide association study to detect the quantitative trait loci (QTL) associated with ESC resistance. Three significant QTL, with two of located on LG1 and one on LG26, and three suggestive QTL located on LG1, LG3, and LG21, respectively, were identified to be associated with ESC resistance. With a well-assembled- and -annotated reference genome sequence, genes around the involved QTL regions were identified. Among these genes, 37 genes had known functions in immunity, which may be involved in ESC resistance. Notably, nlrc3 and nlrp12 identified here were also found in QTL regions of ESC resistance in the channel catfish × blue catfish interspecific hybrid system, suggesting this QTL was operating within both intra-specific channel catfish populations and interspecific hybrid backcross populations. Many of the genes of the Class I MHC pathway, for mediated antigen processing and presentation, were found in the QTL regions. The positional correlation found in this study and the expressional correlation found in previous studies indicated that Class I MHC pathway was significantly associated with ESC resistance. This study validated one QTL previously identified using the second and fourth generation of the interspecific hybrid backcross progenies, and identified five additional QTL among channel catfish families. Taken together, it appears that there are only a few major QTL for ESC disease resistance, making marker-assisted selection an effective approach for genetic improvements of ESC resistance.

Predicted and Observed Responses of a Nonnative Channel Catfish Population Following Managed Removal to Aid the Recovery of Endangered Fishes

AbstractHuman transformation of aquatic systems and the introduction of nonnative species increasingly threaten the persistence of imperiled freshwater fishes. In response, large‐scale mechanical removal of nonnative fishes has been implemented throughout parts of the Colorado River basin to aid recovery of endangered fishes, but the effects of these efforts can be difficult to quantify. Fisheries population models for predicting outcomes of harvest regulations have been widely used to prevent overfishing of commercial and game stocks. Here, we used population models to investigate size‐specific removal efforts needed to overfish a nonnative population of Channel Catfish Ictalurus punctatus and thereby aid recovery of endangered fishes in the San Juan River, New Mexico and Utah. The minimum size of fish that were efficiently captured with electrofishing gear was 280 mm TL, and annual removal rates increased with fish size, ranging from 0.10 for 200‐mm fish to 0.44 for 600‐mm fish. Model results suggested that removal rates should be increased from 0.14 to a range of 0.21–0.34 to cause growth overfishing and should be increased to a range of 0.26–0.29 to cause recruitment overfishing at a minimum electrofishing size limit of 280 mm TL. However, model results indicated that overall population abundance and biomass are being substantially reduced compared to an unmanaged population. In concordance, long‐term monitoring data from 1991 to 2015 demonstrated a decrease in Channel Catfish TL and mass as well as an increase in catch rate variability since removal efforts intensified in 2006. Overall, current rates of removal will probably not achieve collapse of the nonnative Channel Catfish population in the San Juan River, but the reduction in size structure indicates that the population has responded to these efforts.

Assessment of a channel catfish population in a large open river system

AbstractEstimates of dynamic rate functions for riverine channel catfish, Ictalurus punctatus (Rafinesque), populations are limited. The open nature and inherent difficulty in sampling riverine environments and the propensity for dispersal of channel catfish impede estimation of population variables. However, contemporary population models (i.e. robust design models) can incorporate the open nature of these systems. The purpose of this study was to determine channel catfish population abundance, survival and size structure and to characterise growth in the lower Platte River, Nebraska, USA. Annual survival estimates of adult channel catfish were 13%–49%, and channel catfish abundance estimates ranged from 8,281 to 24,261 fish within a 10‐km sampling reach. Channel catfish were predominantly (90%) <age 5 and <400 mm total length, and adult growth was similar to other populations across the species’ range. The channel catfish population characteristics in the lower Platte River are likely a result of a combination of factors including recreational harvest and potential shifts in habitat during different life stages. A multifaceted sampling and analytical approach provided additional information such as movement and abundance estimates and may also help to decipher abiotic and biotic factors that interact when managing fish populations in riverine environments.

Mixed-origins of channel catfish in a large-river tributary

Abstract An understanding of factors responsible for population structure including the origins of individuals from among habitats is fundamental to conservation and management of large-river fishes. The prevalence of population mixing of channel catfish Ictalurus punctatus was evaluated within a large-river tributary environment using information from recent environmental history and natal origin derived from otolith microchemistry. Trace elements in water and otoliths were assessed using univariate and multivariate statistical approaches. Water and otolith trace elements differed among river segments facilitating classification of channel catfish to the river segment of capture. Accuracy of the classification tree model for juvenile channel catfish ranged from 44% to 88%. Recent environmental and natal origin microchemistry signatures suggested the channel catfish population within a large-river tributary comprises individuals from multiple locations. Population demographics of channel catfish is likely influenced by mixing of individuals from across the riverine-network. Consideration of the importance of connectivity between main-stem and tributary systems may, therefore, benefit conservation and management of channel catfish and other large-river fishes displaying similar life-history strategies.

Diversity and genetic origin of introduced channel catfish (Ictalurus punctatus Rafinesque, 1818) to central-west Mexico

The channel catfish is an important aquaculture species in Mexico mostly managed in traditional production systems. The state of Tamaulipas has been the source of diverse populations of channel catfish in the country, however there is no documentary evidence of this. Therefore, the objective of this study was to confirm the genetic origin of populations of channel catfish (Ictalurus punctatus) of west central Mexico by microsatellite DNA markers. The study included four domestic populations from Michoacán, Zacatecas and Jalisco and two reference founder populations from Tamaulipas and Coahuila. The analysis was performed with a panel of 13 microsatellites. Some parameters of diversity and population structure were evaluated. The six populations showed excess of heterozygotes and a coefficient endogamy FIS ≤ -0.014. The analysis of gene structure was determined by a paired comparison populations, and indicated the 5.92% of variation among populations (FST= 0.059, P < 0.001). The assessment approaches identified the population of Tamaulipas as the most likely genetic origin of channel catfish populations currently used in the evaluated states.

Age, Growth, and Mortality of a Trophy Channel Catfish Population in Manitoba, Canada

AbstractThe Red River of the North (Red River) is managed with a unique set of regulations aimed at conserving the age structure and size structure of a trophy Channel Catfish population. Although these regulations have been in place for >20 years, current population dynamics have not been evaluated postregulation. Our objectives were to (1) document dynamic rate functions (i.e., growth and mortality), age structure, and size structure of Channel Catfish in the lower Red River, and (2) compare current population dynamics with historical conditions in the lower Red River and other populations. We documented a maximum age of 27, and ages greater than 20 were common (7%). We estimated an annual mortality rate of 0.19, which was similar to mortality estimates for Channel Catfish in the Red River from the USA. Growth rates for individuals ages 3–10 were similar among our study, historical growth estimates, and upstream estimates. Conservative harvest regulations appear to be preserving the desired age structure and size structure of Channel Catfish in the lower Red River, and this study may provide insight into unique management possibilities for other systems.Received March 11, 2016; accepted August 1, 2016 Published online October 28, 2016

Simulation Modeling to Explore the Effects of Length‐Based Harvest Regulations for Ictalurus Fisheries

AbstractManagement of Blue Catfish Ictalurus furcatus and Channel Catfish I. punctatus for trophy production has recently become more common. Typically, trophy management is attempted with length‐based regulations that allow for the moderate harvest of small fish but restrict the harvest of larger fish. However, the specific regulations used vary considerably across populations, and no modeling efforts have evaluated their effectiveness. We used simulation modeling to compare total yield, trophy biomass (Btrophy), and sustainability (spawning potential ratio [SPR] > 0.30) of Blue Catfish and Channel Catfish populations under three scenarios: (1) current regulation (typically a length‐based trophy regulation), (2) the best‐performing minimum length regulation (MLRbest), and (3) the best‐performing length‐based trophy catfish regulation (LTRbest; “best performing” was defined as the regulation that maximized yield, Btrophy, and sustainability). The Btrophy produced did not differ among the three scenarios. For each fishery, the MLRbest and LTRbest produced greater yield (>22% more) than the current regulation and maintained sustainability at higher finite exploitation rates (>0.30) than the current regulation. The MLRbest and LTRbest produced similar yields and SPRs for Channel Catfish and similar yields for Blue Catfish; however, the MLRbest for Blue Catfish produced more resilient fisheries (higher SPR) than the LTRbest. Overall, the variation in yield, Btrophy, and SPR among populations was greater than the variation among regulations applied to any given population, suggesting that population‐specific regulations may be preferable to regulations applied to geographic regions. We conclude that LTRs are useful for improving catfish yield and maintaining sustainability without overly restricting harvest but are not effective at increasing the Btrophy of catfish.Received February 1, 2016; accepted June 16, 2016

Temporal Trends of Channel Catfish Population Characteristics in the Missouri River, Nebraska

Abstract Channel catfish (Ictalurus punctatus) are a popular target for Nebraska anglers, and the proportion of Nebraska anglers targeting catfish is consistently 50% or greater on an annual basis. Commercial fishing for channel catfish was legal on the Missouri River, in Nebraska, from the 1800s until 1992. Several studies have been published regarding channel catfish population characteristics in this reach prior to the closure of commercial fishing; however, there have been no long-term assessments done post-closure. There is concern among anglers and managers about numbers and size of channel catfish in the Missouri River and a desire to better understand population dynamics in order to better manage channel catfish stocks. The goal of this study was to assess spatial and temporal changes in population characteristics of channel catfish in the Missouri River, Nebraska from 1998 – 2013. Specifically, we asked: (1) did channel catfish population characteristics differ among four reaches of the river fro...