Catfish Populations Research Articles

Significant associations between prolactin gene polymorphisms and growth traits in the channel catfish (Ictalurus punctatus Rafinesque, 1818) core breeding population

The aim of this study was to analyze the effects of the prolactin gene (PRL) on growth traits in channel catfish (Ictalurus punctatus). We sequenced pooled DNA samples from channel catfish to identify single nucleotide polymorphisms (SNPs) in the PRL gene. The identified SNPs were then genotyped in 176 individuals from the G1 core breeding population of catfish using the multiplex SNaPshot method. SNP genotypes and diplotypes of the PRL gene and their associations with body mass and body length traits were also examined. Seven SNPs (g.951A>C, g.1293A>T, g.1359C>T, g.1374A>G, g.1620C>T, g.2675C>T, and g.3369A>G) were identified in introns and noncoding regions, and five of these were successfully genotyped. Seven haplotypes and ten diplotypes occurred in the group of 176 catfish. Association analyses showed that the g.1620 C>T SNP was significantly associated with growth traits in channel catfish, such that individuals with the TT genotype had significantly greater body weights and body lengths than those with CC or CT genotypes (P < 0.05). In addition, the g.3369 A>G SNP showed a significant negative association with growth traits, such that fish with the GG genotype had lower values for both growth traits compared with fish with genotype AA or AG (P < 0.05). Diplotypes H3/H3 and H4/H7 were associated with significantly higher body mass and body length than the other diplotypes (P < 0.01). The results of this study may provide basic data for marker-assisted selection and quantitative trait loci analysis of growth traits in channel catfish.

GENETIC DIVERSITY ANALYSIS OF the first and second generations OF FAST-GROWING STRIPED CATFISH (Pangasianodon hypophthalmus Sauvage,1878) USING MICROSATELLITE ANALYSIS

Genetic diversity is an important aspect of a selective breeding program to produce fish broodstock carrying superior traits such as fast-growing, disease resistant, and other traits. We have carried out a breeding program to produce a fast-growing striped catfish (Pangasianodon hypophthalmus) since 2010. The aim of this study was to evaluate the genetic variation of the first (G-1) and second (G-2) generations of fast-growing striped catfish using microsatellite analysis. The G-1 and G-2 populations were selected individually from populations. DNA samples were collected from 40 ind. fish of each population and analyzed using five microsatellite loci (Pg1, Pg2, Pg3, Pg13, and Pg14). The results showed that the number of alleles per loci in the G-1 and G2 populations ranged from 4 to 7 alleles, with an average of five for each generation. The average of observed heterozygosity of the G-1 population (0.420) was lower than the G-2 population (0.495). Inbreeding level showed that the G-1 population was more inbred than the G-2 population. The study also found that both striped catfish populations had relatively low genetic variation. This result suggests that monitoring of genetic variation and better scheme of good spawning were needed on the next selection program to produce the intended fast-growing striped catfish.

Assessment of legacy and emerging contaminants in an introduced catfish and implications for the fishery.

Since introduction into the Chesapeake Bay watershed in the 1970s, blue catfish (Ictalurus furcatus) populations have increased, impacting native species. One strategy suggested to limit their growing numbers is to expand the existing commercial fishery. However, the promotion of human consumption of this large, omnivorous fish may increase exposure to contaminants of concern (COC). However, there are few published data on contaminants in blue catfish. To evaluate this possibility, we measured COC (PCBs, PBDEs, OCs, Hg) in individual fillets and compared levels to established consumption advisory limits. James River (near Richmond, Virginia) and Upper Potomac River (downstream of Washington DC) fish exhibited higher burdens of most COC than those from the lower James and rural Rappahannock rivers. Fish sex and δ15N values (surrogate for trophic position) did not correlate with COC concentrations. Potomac River fish exhibited greatest δ15N, perhaps related to local wastewater inputs. Despite differences in human population densities among watersheds, fish mercury (Hg) levels were similar. Most fillets surpassed US EPA advisory limits for unrestricted consumption (> 16 meals/month) for Hg and PCBs. Hg and PCB advisories in the region typically restrict consumption to two 220g meals/month. Hence, individuals who rely on fish for a large portion of their diet may be exposed to unacceptable Hg and PCB concentrations. COC levels typically increased with fish length; in particular, fish > 550mm often exceeded unrestricted consumption limits for chlordanes and DDTs. PBDEs, pentachloroanisole, hexachlorobenzene, and mirex levels were generally below established advisories. However, because fish advisories are based on the expected consequences from single contaminants and a single or limited number of toxicological endpoints, consumers face greater risks due to cumulative effects from all coincident COCs, as well as additional exposure pathways, such as other food and air. The additional data on contaminant levels reported here will increase the accuracy of forecasted risks. However, it also illustrates the complexity in communicating the risks from multi-contaminant exposure.

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.

Regional variation in genetic diversity between wild and cultured populations of bighead catfish (Clarias macrocephalus) in the Mekong Delta

Bighead catfish (Clarias macrocephalus) is an important freshwater species for aquaculture and fisheries in Southeast Asia. The species has been domesticated for more than 30 generations in hatcheries, but wild population numbers have declined to “threatened” levels. In this study, genetic diversity was quantified in areas of intensive catfish culture and natural areas of the Mekong Delta, Viet Nam to inform hatchery genetic improvement programs and conservation actions. Fish were collected from three hatcheries and four wild populations in conservation parks (wild-conservation) and seven wild populations in rice fields of aquaculture-intensive areas (wild-farming). Results based on six microsatellite loci showed all populations had relatively high levels of genetic diversity for allelic richness (range 8.10– 10.18), and observed heterozygosity (range 0.708– 0.819). However, genetic diversity was lower in hatchery fish and wild farming populations as evidenced by significantly lower (P ≤ 0.03) allelic richness (9.16 ± 0.27 and 9.27 ± 0.66, respectively) than wild conserved populations (10.01 ± 0.19). Pairwise individuals’ genetic relatedness within three cultured populations (0.013–0.028) and five wild farming populations (0.016–0.039) indicated low potential for inbreeding in the immediate future. Genetic differentiation among populations (FST = 0.017 ± 0.002) indicated a modest level of gene flow, likely due to the expansive river network, straying of hatchery fish, and large-scale transport of wild fish to hatcheries.

Сравнительные исследования роста и развития популяций африканского клариевого сома, репродуцированных в разные сезоны

Сравнительные исследования роста и развития популяций африканского клариевого сома, репродуцированных в разные сезоны

Identification of three Ictalurus species in Mexico using Cytochrome Oxidase I gene sequencing

Channel catfish, Ictalurus punctatus , is one of the most important fish on Mexican aquaculture and despite its productive potential, there is very few information regarding the distribution of Ictalurus species in Mexican territory. Sequencing of Cytochrome Oxidase I gene has proved to be very useful for the identification of fish specimens and sub-products. In the present, we report the molecular identification of 93 feral, commercial and domestic catfish individuals. All domestic fish were positively identified as channel catfish. Commercial samples were identified as Ictalurus punctatus , Ictalurus lupus , and Ictalurus furcatus , providing evidence that catfish represents a generic label for separate fish species. We also report the presence of feral I. punctatus on eight novel locations within Mexican territory, I. lupus on three and I. furcatus in one. Thus, we propose that molecular identification by DNA barcoding represents a powerful tool in the study of catfish populations and sub-products. Normal 0 21 false false false ES-MX X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Times New Roman; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;}

GWAS analysis using interspecific backcross progenies reveals superior blue catfish alleles responsible for strong resistance against enteric septicemia of catfish.

Infectious diseases pose significant threats to the catfish industry. Enteric septicemia of catfish (ESC) caused by Edwardsiella ictaluri is the most devastating disease for catfish aquaculture, causing huge economic losses annually. Channel catfish and blue catfish exhibit great contrast in resistance against ESC, with channel catfish being highly susceptible and blue catfish being highly resistant. As such, the interspecific backcross progenies provide an ideal system for the identification of quantitative trait locus (QTL). We previously reported one significant QTL on linkage group (LG) 1 using the third-generation backcrosses, but the number of founders used to make the second- and third-generation backcross progenies was very small. Although the third-generation backcross progenies provided a greater power for fine mapping than the first-generation backcrosses, some major QTL for disease resistance may have been missing due to the small numbers of founders used to produce the higher generation backcrosses. In this study, we performed a genome-wide association study using first-generation backcrosses with the catfish 690K SNP arrays to identify additional ESC disease resistance QTL, especially those at the species level. Two genomic regions on LG1 and LG23 were determined to be significantly associated with ESC resistance as revealed by a mixed linear model and family-based association test. Examination of the resistance alleles indicated their origin from blue catfish, indicating that at least two major disease resistance loci exist among blue catfish populations. Upon further validation, markers linked with major ESC disease resistance QTL should be useful for marker-assisted introgression, allowing development of highly ESC resistant breeds of catfish.

Evaluation of Unbaited Hoop Nets for Simultaneously Assessing Channel Catfish and Flathead Catfish populations in the Minnesota River

AbstractFisheries managers desire efficient sampling methods with sufficient precision for monitoring ictalurid catfish populations. For this study, I conducted single unbaited hoop‐net surveys in the Minnesota River to evaluate the efficacy of simultaneously assessing stock‐size (≥280‐mm) Channel Catfish Ictalurus punctatus and quality‐size (≥510‐mm) Flathead Catfish Pylodictis olivaris populations. I compared catch rates and length‐frequency distributions among months (April–September) and used resampling procedures to estimate the number of hoop‐net samples needed to achieve desirable precision of catch rate estimates and adequate statistical power. Catch rates (mean ± SE) were 2.1 ± 0.3 fish/net‐night for Channel Catfish and 0.8 ± 0.1 fish/net‐night for Flathead Catfish. Resampling procedures demonstrated that desirable precision (i.e., relative SE ≤ 25) and adequate statistical power (≥0.80 with α = 0.10) to detect 50% reductions in mean catch rates with two‐tailed t‐tests could be achieved for both species with as few as 68 hoop‐net samples during August. Unbaited hoop nets are effective for simultaneously assessing Channel Catfish and Flathead Catfish populations in the Minnesota River, and conducting surveys during August provides the best balance between catch rate and precision while minimizing perceived environmental and behavioral biases. However, the amount of sampling effort needed to detect small population changes (&lt;50%) and to collect sufficient sample sizes for age and growth analyses may be logistically prohibitive. This study emphasizes the importance of evaluating precision and statistical power of sampling methods so that fisheries managers can identify the most suitable methods for their specific objectives.

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.

Spatial Variability and Macro‐Scale Drivers of Growth for Native and Introduced Flathead Catfish Populations

AbstractQuantifying spatial variability in fish growth and identifying large‐scale drivers of growth are fundamental to many conservation and management decisions. Although fish growth studies often focus on a single population, it is becoming increasingly clear that large‐scale studies are likely needed for addressing transboundary management needs. This is particularly true for species with high recreational value and for those with negative ecological consequences when introduced outside of their native range, such as the Flathead CatfishPylodictis olivaris. This study quantified growth variability of the Flathead Catfish across a large portion of its contemporary range to determine whether growth differences existed between habitat types (i.e., reservoirs and rivers) and between native and introduced populations. Additionally, we investigated whether growth parameters varied as a function of latitude and time since introduction (for introduced populations). Length‐at‐age data from 26 populations across 11 states in theUSAwere modeled using a Bayesian hierarchical von Bertalanffy growth model. Population‐specific growth trajectories revealed large variation in Flathead Catfish growth and relatively high uncertainty in growth parameters for some populations. Relatively high uncertainty was also evident when comparing populations and when quantifying large‐scale patterns. Growth parameters (Brody growth coefficient [K] and theoretical maximum average length [L∞]) were not different (based on overlapping 90% credible intervals) between habitat types or between native and introduced populations. For populations within the introduced range of Flathead Catfish, latitude was negatively correlated withK. For native populations, we estimated an 85% probability thatL∞estimates were negatively correlated with latitude. Contrary to predictions, time since introduction was not correlated with growth parameters in introduced populations of Flathead Catfish. Results of this study suggest that Flathead Catfish growth patterns are likely shaped more strongly by finer‐scale processes (e.g., exploitation or prey abundances) as opposed to macro‐scale drivers.

Identification and analysis of snps in population of Vietnamese catfish (pangasianodon hypophthalmus), using next generation sequencing and snp validation

Tra catfish Pangasianodon hypophthalmus is a commercially important aquaculture species in the Mekong Delta Vietnam accounting for approximately of Vietnam freshwater fish production However the food trade globalization and the growing demand for selected varieties of food have led to the intensification of commercial fraud especially in the form of substitution species and mixing with cheaper taxa DNA bar coding methods have shown a potential well proven molecular approach to assess the authenticity of food items In this study we utilized high throughput NextSeq sequencing to capture and identified SNP markers on wild and farming catfish individuals from Vietnamese provinces e g An Giang Dong Thap Can Tho Tien Giang Ben Tre Hau Giang Vinh Long and Ho Chi Minh City and international locations of Cambodia Thailand and Bangladesh Stringent filtering of SNP calling parameters resulted in SNP loci represented across all countries We utilized the VCF tools to validate two panels of SNPs selected from the NGS data Selection criteria included SNPs shared between catfish s Vietnam and international populations and SNPs specific to each population A total of and SNPs were filtered in Vietnamese and international catfishes respectively the final special SNPs were detected SNP validation by using Sanger sequencing and PCR showed a result of per SNPs was confirmed successfully in individuals from Vietnamese catfishes The first times our results provide genotype informative marker loci in Vietnamese Tra catfish in order to approach molecular traceability in aquaculture species with minimal previous genetic information

Age‐0 blue catfish habitat use and population demographics in the middle Mississippi River

AbstractThe demographics (e.g. hatch time, growth and mortality) and habitat (macrohabitat and mesohabitat) use of age‐0 blue catfish Ictalurus furcatus (Lesueur) were evaluated in the un‐impounded reach of the middle Mississippi River during 2003–2010. Each year, island complexes and adjacent main river habitats were trawled, and 7,373 age‐0 blue catfish (10–144 mm total length) were collected. Blue catfish hatch timing varied slightly across years and generally began in June and ended in August. Age‐0 blue catfish growth rates and instantaneous mortality rates differed among years. Catch rates of age‐0 blue catfish were highest in side channels and around islands, whereas main channel habitats were infrequently occupied. Regarding mesohabitat use, age‐0 blue catfish frequently occupied low velocity areas (i.e. 0.3–0.4 m/s) of shallow depth (i.e. 1–4 m) and sand substratum. This study has provided insight into age‐0 blue catfish population dynamics and has highlighted the importance of specific habitat characteristics in large rivers that may aid in recruitment of this species.

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%) &lt;age 5 and &lt;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.

Demographics and Interstate Management Implications for Flathead Catfish in the Lower Wabash River, Illinois and Indiana

AbstractFlathead Catfish Pylodictis olivaris in the lower Wabash River, Illinois and Indiana, are currently exploited by anglers and commercial fishers under the same fishing regulation; however, the regulations differed between the states prior to 2015. We assessed demographics of Flathead Catfish in this interstate river to gain baseline information to create models to test for sustainable exploitation rates under the new regulation and several hypothetical scenarios. During 2010–2012, we sampled 951 Flathead Catfish (length = 343 ± 5.6 mm [mean ± SE], weight = 914.5 ± 55.6 g, age = 3.5 ± 0.07 years) using pulsed‐DC electrofishing, AC electrofishing, commercial harvest, and hoop nets. Mean relative weight of Flathead Catfish was greater than 100%, and proportional size distribution indices (electrofishing = 35, hoop netting = 54) suggested a quality fishery. Total annual mortality (electrofishing = 0.48, hoop netting = 0.54) was similar to estimates in other Midwestern rivers. Yield‐per‐recruit models predicted that growth overfishing may occur over time under the current regulation; however, demographic metrics relate to recreational and commercial creel assessments. Our results suggest that the current minimum length limit could be raised to increase yield and reduce exploitation. Our findings also demonstrate several useful field and modeling techniques to assess catfish (family Ictaluridae) populations in environments that are difficult to sample and that lack fishery‐independent information.Received January 11, 2017; accepted August 31, 2017 Published online October 20, 2017

Молекулярна діагностика патогенних та умовно-патогенних бактерій в популяціях цінних видів риб

The purpose. To study molecular-biological features of causal organisms of contagions of fishes of bacterial etiology. Methods. Microbiological, molecular-biological, icthyological. Results. Complex analysis is carried out, and series of conditional-pathogenic and pathogenic bacteria is determined in populations of rainbow trout, sterlet, European catfish, and carp, cultivated in Ukraine. Analysis of a gene 16S rRNK of these bacteria is carried out. Conclusions. Methods of identification are elaborated of conditional-pathogenic and pathogenic bacteria on the basis of polymerase chain reaction.

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.

MHC-II MARKER POTENTIAL LINKED TO MOTILE AEROMONAD SEPTICAEMIA DISEASE RESISTANCE IN AFRICAN CATFISH (Clarias gariepinus)

One of the important issues in catfish farming is motile aeromonad septicaemia (MAS) disease caused by the bacterium Aeromonas hydrophila. This study aimed to find the MHC-II marker potential for marker-based selection to generate MAS disease resistance of African catfish. PCR method was applied to identify catfish (body length: 7-8 cm) population that have MHC-II marker. Fish with and without the marker were then challenged by intraperitonially injecting of 0.1 mL/fish with A. hydrophila (105 cfu/mL). The results showed that the survival of fish having MHC-II marker (77.50 ± 4.00%) was higher than that of fish without the marker (53.33 ± 4.77%). Fish carrying MHC-II marker fish has also higher total erythrocytes, total leukocytes, phagocytic activity, and hematocrit levels than that of fish without the marker. The PCR results using specific primer for MHC-II showed a specific DNA band of 426 bp in fish having the marker, while there were no DNA bands in fish without the marker. Results of the PCR analyses showed that the percentage of progenies carrying MHC-II marker was 80%, while progenies from broodstock without the marker was 0%; this indicated that MHC-II marker could be inherited to the offsprings. Thus, the MHC-II marker could be used as a molecular marker of MAS disease resistance catfish.

Relative Abundance, Growth, and Mortality of the White Catfish, Ameiurus catus L., in the St. Marys River

Declines in Ameiurus catus (White Catfish) abundance throughout much of their native range have been attributed to the rapid colonization of invasive Ictalurus furcatus (Blue Catfish) and Pylodictis olivaris (Flathead Catfish). Because of the potential for imperilment throughout a majority of its native range, we examined the White Catfish population in the St. Marys River, GA, one of the few locations where the catfish assemblage is still native. White Catfish (n = 1244) dominated the ictalurid assemblage, making up 79% of the catfish caught in the St. Marys River. Overall, length of White Catfish varied from 89 to 486 mm TL, with the majority of fish between 220 and 260 mm. Ages of White Catfish varied from 1 to 11 years but was dominated by the 2012 year class (age 3). We estimated a von Bertalannfy growth model for the population (L∞ = 486 mm TL, K = 0.246, t0 = -0.290). Catch-curve analysis indicated that White Catfish had a 45% annual survival rate in 2015. This White Catfish population assessment will provide biologists with baseline parameters to aid in future management and conservation of this declining native species.

Tidal Habitats Support Large Numbers of Invasive Blue Catfish in a Chesapeake Bay Subestuary

The introduction of a non-native freshwater fish, blue catfish Ictalurus furcatus, in tributaries of Chesapeake Bay resulted in the establishment of fisheries and in the expansion of the population into brackish habitats. Blue catfish are an invasive species in the Chesapeake Bay region, and efforts are underway to limit their impacts on native communities. Key characteristics of the population (population size, survival rates) are unknown, but such knowledge is useful in understanding the impact of blue catfish in estuarine systems. We estimated population size and survival rates of blue catfish in tidal habitats of the James River subestuary. We tagged 34,252 blue catfish during July–August 2012 and 2013; information from live recaptures (n = 1177) and dead recoveries (n = 279) were used to estimate annual survival rates and population size using Barker’s Model in a Robust Design and allowing for heterogeneity in detection probabilities. The blue catfish population in the 12-km study area was estimated to be 1.6 million fish in 2013 (95% confidence interval [CI] adjusted for overdispersion: 926,307–2,914,208 fish). Annual apparent survival rate estimates were low: 0.16 (95% CI 0.10–0.24) in 2012–2013 and 0.44 (95% CI 0.31–0.58) in 2013–2014 and represent losses from the population through mortality, permanent emigration, or both. The tagged fish included individuals that were large enough to exhibit piscivory and represented size classes that are likely to colonize estuarine habitats. The large population size that we estimated was unexpected for a freshwater fish in tidal habitats and highlights the need to effectively manage such species.