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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.

Invasive alien species often affect native ecosystems worldwide. In Japan, the channel catfish Ictalurus punctatus is an invasive species in rivers. However, information regarding its feeding habits in rivers around dam reservoirs is still scarce. Thus, in this study, we assessed the feeding habits of I. punctatus collected from the Nunome River, a secondary tributary of the Yodo River, downstream of the Nunome Dam reservoir. Standard length and weight of the collected individuals were measured, and their stomach contents were analyzed under a stereomicroscope to identify prey species. Moreover, stable isotope analysis was conducted to determine their trophic niche. Overall, I. punctatus was shown to feed on a variety of food resources derived from the riparian forest and river ecosystem; in particular, algae represented 78.8% of its stomach contents. However, stable isotope analysis suggested that I. punctatus depended on benthic insects and fish to ensure adequate body composition, whereas algae were not assimilated by I. punctatus. Among benthic insects, I. punctatus relied on trichopteran larvae such as Macrostemum radiatum, which appears downstream of the dam reservoir and utilizes plankton algae from the dam. In conclusion, these findings provide additional clues for a better understanding of I. punctatus feeding activity and its relationship with its surrounding ecosystem.

In the process of work on the reproduction of the channel catfish Ictalurus punctatus (Raf.) In the conditions of LLC «Belovsky Fish Industry», the main problem was the timely production of high-quality offspring, associated with differences in preparation for spawning of females and males. In this regard, the purpose of the work: to develop and test various options for carrying out spawning campaigns, including those using various drugs for hormonal stimulation of manufacturers. The results of testing Nerestin preparations in 2006–2008 are presented. In 2006, the drug Nerestin-5x (N5x) was tested. The main problem was identified: 80% of the injected females matured, but the passive males did not start fertilization. It was proposed to adjust the total dose of H5x for females towards a decrease, depending on the degree of their initial readiness, and for males — towards an increase. In 2007, drugs H5x and H7A were tested. A change in the injection scheme of males in 2007 compared to 2006 (an increase in the total dose to the norm of females, but with the use of the drug H5x, and not H6A or H7A during the first two injections) increased the readiness of males for spawning slightly. In 2008, males were brought into the hatchery one month earlier than females, increasing the maturation period of males and changing the temperature rise schedule to prepare for spawning. The drug H7A was used. Despite the increase in the total dose of H7A for males to the total dose for females, their readiness for spawning was still insufficient. To a greater extent, the readiness of males was influenced by an increase in the period of keeping and feeding. The conclusion is drawn that preparations H7 and H7A are quite applicable for artificial reproduction of channel catfish, but the technique of application must be improved by adjusting the conditions of pre-spawning maintenance of producers and the injection scheme.

Although a concerted effort in catfish nutrition research in the United States did not begin until the late 1950s/early 1960s, the genesis of both the catfish industry and catfish nutrition research is rooted in studies conducted early in the 20th century. Thus, a historical view delineating the progression of channel catfish, Ictalurus punctatus, nutrition from 1900 to the present is given. Notable nutrition research programs, as well as significant events and accomplishments, will be examined.

Mortality of fish early life stages was measured in a pressure vessel to simulate vertical displacement within the water column. Mortality was measured for three pressure regimes for four fish species: larval bigmouth buffalo Ictiobus cyprinellus, larval blue catfish Ictalurus furcatus, juvenile bluegill Lepomis macrochirus, and juvenile largemouth bass Micropterus salmoides. The maximum pressure‐change tested, 344.8 kPa, equivalent to a 35.2 m displacement of fish within the water column, did not cause significant mortality of larvae or juveniles. Since 32.5 m exceeds depths in most inland navigation channels and possibly the depth to which rapid propeller induced water mixing occurs, the range of pressure changes that could be experienced by early life stages during towboat mixing of the water column will not result in significant mortality.

Cryopreservation of genetic material can become an important tool for user groups in imperiled fishes, wild fisheries, aquaculture, and biomedical research. Persistent challenges within aquatic species cryopreservation are standardization and reliable collection of diverse, high quality samples. The overall goal of this study was to work with different user groups and cryopreserve sperm on-site at their facilities to evaluate the uses and challenges of a mobile laboratory with high-throughput and quality control capabilities comparable to those of a specialized centralized facility. The objectives were to demonstrate collection and cryopreservation of sperm of: 1) large-bodied freshwater Blue Catfish (Ictalurus furcatus) for aquaculture; 2) small-bodied freshwater Xiphophorus for biomedical and imperiled repository development, and 3) saltwater Red Snapper (Lutjanus campechanus) for wild fisheries research. Over the course of this project, the mobile laboratory traveled more than 4,000 km collecting germplasm from more than 650 male fishes. A total of 136 Blue Catfish were processed in 2015 and 2016 resulting in a total of 6,146 0.5-mL French straws. A total of 521 males from 11 different species in the genus Xiphophorus were processed over 4 d in 2015 resulting in a total of 488 0.25-mL French straws. And, a total of 17 Red Snapper males were processed during 2015 resulting in a total of 316 0.5-mL French straws. This is the first development of a mobile laboratory with high-throughput capability for aquatic species. User groups would no longer be limited to germplasm resources that can only be shipped as samples or transported as live animals to a central cryopreservation facility. Mobile laboratories create opportunities to collect higher quality germplasm, provide access to new species, and enable direct cooperation, including training, with a wide variety of user groups and applications.

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.

Plastic is pervasive in modern economies and ecosystems. Freshwater fish ingest microplastics (i.e., particles

Piscivorous birds are the primary source of catfish (Ictalurus spp.) depredation at aquaculture facilities in northwestern Mississippi. Of particular concern is the Double-crested Cormorant (Phalacrocorax auritus), which can cost aquaculture producers millions of dollars annually through the depredation of cultured fish. Historical research conducted in the early 2000s estimated cormorant use of aquaculture ponds in the region, but aquaculture area has decreased by more than 70% since those estimates were made. With less aquaculture available, we predicted cormorant densities on aquaculture would be greater today than historically. Applying a similar methodology as in historical studies, we used aerial surveys to collect data on cormorants at night roosts and using catfish aquaculture ponds during 3 consecutive winter seasons, beginning in 2015. Although the mean annual number of cormorants at roosts in the Delta during our study was 64% less than historically, we found no significant change in densities on aquaculture, suggesting that aquaculture area is likely the factor influencing cormorant occurrence in northwestern Mississippi. During contemporary surveys we also measured the abundance of Great Blue Herons (Ardea herodias) and Great Egrets (A. alba) on the aquaculture clusters, and built predictive models of abundance relative to variables associated with forage at and surrounding the clusters. We found abundance of all 3 species was strongly related to the amount of aquaculture area both within and surrounding a cluster, although patterns varied by species. Cormorant abundance was also greater on clusters with proportionately more food fish (≥20 cm in length) than fingerlings (

Fish mercury concentrations have received considerable attention due to human health implications. Fish mercury concentrations are variable within and among systems due to a suite of biotic and abiotic influences that vary among regions and are difficult to predict. Understanding factors associated with variability in fish mercury concentrations would help guide consumption advisories. Mercury concentrations in channel catfish (Ictalurus punctatus, n = 205), flathead catfish (Pylodictis olivaris, n = 123), northern pike (Esox lucius, n = 60), smallmouth bass (Micropterus dolomieu, n = 176), and walleye (Sander vitreus, n = 176) were assessed in ten Iowa rivers and relationships with land use, water chemistry, and fish characteristics were explored. Mercury concentrations were generally low (mean among all species = 0.17 mg/kg, n = 740) but higher in flathead catfish, northern pike, smallmouth bass, and walleye than channel catfish and were positively related to fish length, age, trophic position, and δ13C signatures. Phosphorus, sulfate, and percent open water and grassland were negatively related to fish mercury concentrations, whereas water hardness, nitrogen-ammonia, Human Threat Index, and percent wetland and forest were positively related to fish mercury concentrations. Fish collected from the Paleozoic Plateau ecoregion in northeast Iowa had higher mercury concentrations than other ecoregions in Iowa. Combined, these factors explained 70% of the variation in fish mercury concentrations. This study provides a comprehensive analysis of abiotic and biotic factors influencing fish mercury concentrations in lotic ecosystems at the individual and system scale that will help guide fish consumption advisories.

Tagging protocols that result in high tag retention will benefit fisheries professionals who use telemetry data. Ictalurid catfish historically have had very poor telemetry tag retention. Here, we use these difficult-to-tag taxa to address two research objectives. First, we evaluated our field-based internal tagging methodology by quantifying six tag retention metrics using data from 48 acoustically-tagged blue catfish (Ictalurus furcatus) released into Milford Reservoir, KS, USA. Second, to better understand the results of this field evaluation, we evaluated tag retention and survival in the hatchery for the closely-related channel catfish (I. punctatus). Field and hatchery studies provided complementary information. Eighty percent of tagged blue catfish were detected at the end of our 5-mo field study (1,139,402 = total detections; 24,243 = average detections per fish). A 13-week hatchery evaluation of our field methodology also had high tag retention (100%). Hatchery treatments that used a lateral-ventral incision had higher tag retention and survival than those treatments that included a mid-ventral incision. Time invested in training, protocol refinement, and field organization were also important. Furthermore, monitoring the surgical history and recovery of individual fish allowed us to correct problems before mortality occurred. Because a need exists for a range of internal tagging methodologies that are effective on an assortment of fish species tagged under a variety of circumstances, our high tag retention methodology may be useful to the expanding research community that studies native and non-native catfish, as well as, other telemetry researchers who seek beneficial refinements to their tagging protocols.

Systematic descriptions of North American Miocene freshwater fishes are extremely uncommon, with those from the Gulf Coastal Plain region being completely absent. In this study we examined 324 hist...

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 220 g 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 > 550 mm 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.

We examined why the lower Little Colorado River (LCR), Arizona continues to be dominated by four native fish species despite decades of encroachment by nine nonnative species. Most perennial flow begins at Blue Spring, located at river kilometer (RKM) 20.74 above the LCR's mouth, which is supplemented downriver by other springs. Blue Spring's water is extremely supersaturated with dissolved CO2 (658 mg/L), and at baseflow the CO2 concentrations apparently functioned as a fish-barrier for about 1 km further downriver until it outgassed to 288 mg/L. Thereafter, CO2 outgassed to 202 mg/L by the top of Chute Falls (RKM 14.20) and 76 mg/L near the river's mouth. Chute Falls, and high CO2 levels above it, obstruct upriver, but not downriver, fish movements; however, we still captured fishes from eight nonnative species above this falls. Our findings indicate most warmwater nonnative fishes in the LCR were immigrants from upriver sources within and bordering the intermittent corridor that invaded the system during floods, while most coldwater trout invaded from the Colorado River. Most nonnative species failed or were severely limited at reproducing progeny in the LCR, except occasionally by channel catfish Ictalurus punctatus and fathead minnow Pimephales promelas in the lower 13.57 km corridor, which was likely related to CO2. Correlation tests suggested severe flood and/or suspended sediment regimes reduced populations of fathead minnows, red shiners Cyprinella lutrensis, and plains killifish Fundulus zebrinus in the LCR. Conversely, severe suspended sediment regimes (especially ≥60,000 mg/L) increased channel catfish, black bullhead Ameiurus melas, and common carp Cyprinus carpio, hypothetically by paralyzing these fishes upriver, whereby many drifted downstream and recovered in the lower LCR; however, their abundances decreased after prolonged periods of high CO2. Nonnative fishes are controlled in the LCR by the system's endemic abiotic conditions.

Globally, invasive species cause extensive economic damage and are a major threat to biodiversity. Generalist species are particularly dangerous invaders, as they can thrive in degraded habitats and endure environmental stochasticity, often outcompeting more specialized native taxa. Blue catfish Ictalurus furcatus were first introduced into the Chesapeake Bay during the 1970s, and now form dense populations in several tidal rivers. Despite being labeled as a dangerous invasive, the feeding ecology of this species is largely unknown. We used a stratified random design to collect stomachs from 16,110 blue catfish in tidal freshwater, oligohaline, and mesohaline segments of the James, Pamunkey, Mattaponi, and Rappahannock Rivers. Indices of diet breadth and omnivory reveal that blue catfish are generalist omnivores with some of the highest diet breadths ever observed in an estuarine fish species, while trophic level calculations demonstrate that blue catfish are a mesopredator occupying lower trophic levels than previously claimed. Cumulative prey curves revealed that large numbers of stomachs are necessary to adequately characterize the diet of blue catfish, thus previous diet descriptions of this species should be considered with caution. Blue catfish feed primarily on invasive aquatic vegetation and Asian clams, though the economically-valuable blue crab Callinectes sapidus is also consumed regularly. While the per capita impact of blue catfish on imperiled native species appears to be low, this impact could still be substantial due to high population densities.

Ictalurus furcatus (Blue Catfish) provide trophy recreational fishing opportunities in Virginia's tidal rivers; however, potential ecological impacts are of concern. We used mark-recapture techniques and electrofishing in 2007 and 2014 to estimate Blue Catfish density and biomass in Powell Creek. A 66% decline in fish density occurred between 2007 (708 fish/ha) and 2014 (239 fish/ha) and biomass declined by 31% over the same timeframe (266 kg/ha to 185 kg/ha). These findings are supported by long-term monitoring trends in the tidal James River. Here, we provide: (1) data relative to temporal shifts in abundance and biomass, (2) data for use in subsequent population-dynamics analyses, and, (3) points of caution when assuming temporally static populations for introduced species. We demonstrated the feasibility of low-frequency electrofishing and mark—recapture methods to estimate Blue Catfish abundance, and recommend use of the approach where catfish abundance estimates are important.

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.

Estimates 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%)

The 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.

There has been strong interest in the use of peracetic acid (PAA) in aquaculture as it can be used to disinfect water and hard surfaces and thereby eliminate or lower the burden of fish pathogens. Unfortunately, there has been little research on the toxicity of PAA to fish. Twelve species of fingerling fish that are important to aquaculture were exposed to PAA for 24 h in static toxicity bioassays in well water. These fish were: fathead minnow, Pimephales promelas; black-nose crappie, Pomoxis nigromaculatus; bluegill, Lepomis macrochirus; blue tilapia, Oreochromis aureus; channel catfish, Ictalurus punctatus; golden shiner, Notemigonus crysoleucas; goldfish, Carassius auratus; grass carp, Ctenopharyngodon idella; largemouth bass, Micropterus salmoides; rainbow trout, Oncorhynchus mykiss; sunshine bass, Morone chrysops × M. saxatilis; and walleye, Sander vitreus. Median lethal concentration (LC50) values were estimated with the trimmed Spearman–Karber method using nominal PAA concentrations. The mean 24-h LC50 values ranged from 2.8 to 9.3 mg/L PAA. Fathead minnow were very sensitive and blue tilapia were very tolerant to PAA exposure; LC50 values of other species tested were within the range of 4.1–6.2 mg/L PAA. More importantly, the 24-h no-observed-effect concentration (NOEC) ranged from 1.9 to 5.8 mg/L PAA; the NOEC would be considered as the safe range for culturists to investigate the use of PAA. Decreased alkalinity/hardness increased the toxicity of PAA, while a small increase of dissolved organic content had no effect on PAA toxicity. Results of the present study are important information on the safe application of PAA for the aquaculture industry.

Bolbophorus damnificus (Digenea: Bolbophoridae) causes significant economic losses in catfish aquaculture in the southeastern USA. To determine mortality trends associated with B. damnificus exposure, three separate disease challenges were conducted. The first challenge exposed channel catfish, Ictalurus punctatus, fingerlings (7–13 cm) to approximately 285 B. damnificus cercariae/L, while the second exposed fish to approximately 215 cercaria/L. Fish were monitored for morbidity and mortality for 28 d. In both studies, mortality first occurred 8 d postchallenge (PC) and peaked at 9 and 10 d PC, respectively. Mortality had subsided by 14 d PC, with only sporadic mortality occurring >15 d PC. Dead and moribund fish presented with lesions consistent with B. damnificus infection. A third challenge was performed to record histological changes associated with parasite development from initial exposure up to the cessation of mortality. Catfish (2–5 cm) were exposed as described above to a range covering 0, 35, 70, 100, 150, 175, and 215 cercariae/L. Each day, two fish were sampled from each treatment. Mortality trends were consistent with previous challenges. The mortality window coincided with parasite encapsulation, neovascularization, and development of the host-derived cyst, suggesting that morbidity and mortality are linked to host pathophysiological changes in response to metacercariae encapsulation.

This study used microsatellite loci to provide evidence of isolation by distance and an effect of artificial impoundments on the genetic diversity of Channel Catfish Ictalurus punctatus from the Wabash and Ohio rivers. The Wabash River is the longest free-flowing river east of the Mississippi River in the USA, and the Ohio River is highly impounded, yet both rivers support large Channel Catfish fisheries. There was a significant positive relationship between genetic differentiation and geographic distance indicating isolation by distance. Clustering with the programs, STRUCTURE and GENELAND, and principal component analysis revealed multiple genetic clusters, and several sites had results consistent with adults existing as mixtures of genetic groups. These results suggest that the rate of straying among reproductive sites or dispersal is dependent on geographic distance. Channel Catfish from the unimpounded Wabash River had higher genetic diversity (Ho and He) than that from the impounded Ohio Riv...

We evaluated freeze brands on Channel Catfish Ictalurus punctatus and hybrid catfish (female Channel Catfish × male Blue Catfish I. furcatus) to determine suitability of the technique for identification of year-class on ictalurid catfishes. Freeze brands were applied to fish in a hatchery setting, and adipose fins were removed as a secondary mark. Marked fish were stocked into two Kansas reservoirs within 3 d after marking. Fish were sampled with a suite of gear types for 3 years after the initial stocking in 2013. All captured catfish were observed for the presence of a freeze brand and an adipose fin. A logistic regression model estimated 80% brand retention for Channel Catfish through 460 d. The logistic regression model for hybrid catfish brand retention as a function of days at large was not significant, but retention remained near 80% throughout the 3-year study period. Results suggest that freeze brands are suitable for marking Channel Catfish and hybrid catfish in natural systems when mark...

Members of the genus Edwardsiella are important pathogens of cultured and wild fish globally. Recent investigations into the phenotypic and genotypic variation of Edwardsiella tarda have led to the segregation of E. tarda into three distinct taxa: E. tarda, Edwardsiella piscicida, and Edwardsiella anguillarum. In catfish aquaculture in the southeastern USA, E. piscicida has been more commonly associated with disease than E. tarda or E. anguillarum, and recent research has demonstrated E. piscicida to be more pathogenic in channel catfish than E. tarda or E. anguillarum. Anecdotal reports from industry suggest an increased prevalence of E. piscicida associated with the culture of channel (♀) × blue (♂) hybrid catfish. This work investigated the comparative susceptibility of channel catfish, blue catfish, and their hybrid cross to molecularly confirmed isolates of E. tarda, E. piscicida, and E. anguillarum. There was significantly higher mortality in hybrid catfish compared to channel catfish following intracoelomic injection of E. piscicida. To our knowledge, E. piscicida is the first bacterial pathogen to demonstrate increased pathogenicity in hybrid catfish compared to channel catfish.

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.

This study examined four experimental diets with different protein concentrations and sources for pond-raised fingerling hybrid catfish, ♀ Ictalurus punctatus × ♂ Ictalurus furcatus. A 35% protein diet with fishmeal was used as the control diet. Test diets were 32 and 28% all-plant-protein diets and a 28% protein diet with porcine meat, bone, and blood meal. Small fingerlings with a mean initial weight of 2.9 g/fish were stocked into 20 earthen ponds (0.04 ha) at a density of 172,970 fish/ha. They were fed once daily to apparent satiation for 107 d. No significant differences were observed for total diet fed, gross yield, final weight, survival, or condition factor among dietary treatments. However, fish fed the 28 and 32% all-plant-protein diets had a significantly higher feed conversion ratio than fish fed the 35% protein diet with fishmeal. There were no significant differences in chlorophyll a and nitrite concentrations in the pond water, but ponds receiving the 35% protein diet had significantly higher ammonia than those receiving 28% protein diets. Economic analysis suggested potential cost savings by using low-protein and all-plant-protein diets for hybrid catfish fingerling production.

The channel catfish virus (CCV) is a pathogenic herpesvirus that infects channel catfish Ictalurus punctatus in pond aquaculture in the southeastern USA. Mannose-binding lectin (MBL), an innate immune protein, could play an important role in the innate response of channel catfish by binding to CCV. Cell cultures of CCV were grown in channel catfish ovary cells (CCOC). A dot-immunoblot enzyme-linked immunosorbent assay was done to determine the binding ability of 5 mo old channel catfish serum MBL (26.2 µg ml-1) to CCOC infected with CCV. Two separate nitrocellulose membrane blotting techniques were done using uninfected and infected CCOC. The uninfected CCOC decreased by 29.3 and 33.4% in their binding of channel catfish MBL when compared with infected CCOC using the 2 membrane procedures. The combined average binding ability of channel catfish MBL towards infected CCOC was therefore 31.4% greater when comparing the infected and uninfected CCOC. Normalization equation values of MBL for the 5 mo old catfish were compared for the 2 membrane binding procedures. The 2 normalization values were very close (142 and 150) in binding ability of MBL to the infected CCOC. The 5 mo catfish serum had twice the concentration of MBL (26.2 µg ml-1) compared to 7 mo catfish serum (13.2 µg ml-1), and the binding percentage of 5 mo serum was 2.4 times greater in infected than in uninfected cells. This demonstrates that the binding of channel catfish serum MBL to CCV is concentration dependent and is related to serum concentrations of MBL.

Production of channel catfish, Ictalurus punctatus, female × blue catfish, Ictalurus furcatus, male hybrids has increased dramatically in the USA. Hybrid production requires surgical removal and maceration of blue catfish testes. Farmers report individual and seasonal variation in blue catfish testes development, and understanding the factors influencing testes development could improve hybrid catfish production. Effects of season (mid-May vs. mid-June), strain (DB however, there were males from each strain with good quality testes in June. GSI, sperm/g of testes, percent motility, and motile sperm/g of testes were positively correlated. Information from this study provides a better understanding of factors influencing testes development in blue catfish.

The channel catfish ( Ictalurus punctatus ) ♀ × blue catfish ( Ictalurus furcatus ) ♂ hybrid catfish has superior performance in respect to survival, growth rate, feed conversion, low dissolved oxygen, and fillet yields compared to its parent species. Currently the demand for hybrid fingerlings is greater than available supply. Selective breeding for early spawning could extend the spawning season to partially address this problem. Under commercial conditions and using natural open pond spawning, the Thompson line of channel catfish spawns earlier at its location than other strains at their home farms. Over a 4-year period the Thompson line was compared to the Kansas strain and AR line for fry production in the early spawning season using induced spawning with luteinizing hormone-releasing hormone analogue implants to induce ovulation, followed by hand stripping, and in vitro fertilization techniques. Relative reproductive performance was variable among years, but in general, fry output of the three strains was similar and relatively high, with the 3-year average of both Thompson and Kansas strains being approximately 2500 fry/kg. The observed fry output of Thompson was about 15% higher than that for Kansas, which was not significantly different because of the high variation among years. The early spawning of the Thompson line appears to be due to an environmental effect, related to genotype-environment interactions or natural spawning and response to induced spawning are actually two different traits. Strains of more northerly origin might be evaluated to achieve the goal of better response to early induced spawning.

Salinity tolerance of yolk-sac larvae and swim-up fry of channel catfish (Ictalurus punctatus), blue catfish (I. furcatus), and hybrid catfish (channel catfish ♀ × blue catfish ♂) was investigated at 0, 3, 6, and 9 ppt salinity. One-hundred percent mortality occurred at 9 ppt. Survivals were different (P hybrid catfish > channel catfish for salinity tolerance. Long-term survival of hybrid fry was better than that of the parent species at 0 ppt salinity, but highest for channel catfish at 3 ppt and 6 ppt with the hybrid being intermediate. NaCl had a negative effect on survival rate of yolk sac larvae starting at 3 ppt and for swim-up fry at 6 ppt. Genotype × environment interactions occurred for growth as hybrids grew faster than channel catfish and blue catfish at 0 ppt. Raising salinity to 3 ppt greatly increased the growth rate (50–75%) of channel catfish and blue catfish, but only slightly (10%) for hybrid catfish, which were still larger than the parent species. 6 ppt was detrimental to yolk-sac larvae and swim-up fry. These results help identify the saline environments that might be suitable for long-term growth and disease resistance of ictalurid catfish, and reveals changes in salinity tolerance during development. Statement of relevance The life stages of channel, blue and hybrid catfish were not previously studied for tolerance of sodium chloride and genotype-environment interations were observed indicating the ideal environment for culture or disease treatment varies among these genetic groups. Heterosis of the hybrids almost disappeared at 3 ppt and growth of channel catfish was greatly enhanced at 3 ppt. Greater Ich resistance of hybrids compared to parents at 0 ppt contradicted earlier reports at older life stages.

Blue catfish (Ictalurus furcatus) have been widely introduced throughout the United States and are invasive in Chesapeake Bay. Despite this proliferation, little is known about the diet of this large, predatory catfish. We used stratified random sampling to collect stomachs from 14,488 blue catfish in Chesapeake Bay. Canonical correspondence analysis (CCA) was used to identify key drivers of the diet of blue catfish, and generalized additive models (GAMs) were used to explore trends in rates of predation by blue catfish on depleted or commercially valuable native species, including American shad (Alosa sapidissima), blueback herring (A. aestivalis), alewife (A. pseudoharengus), American eel (Anguilla rostrata), and blue crab (Callinectes sapidus). Results of CCA reveal that diets were significantly correlated with season, salinity, and total length (TL) of blue catfish, and those from our GAMs reveal the circumstances associated with greater predation on these species. For example, we found that Alosa species were most susceptible to predation by large catfish (>600 mm TL) in freshwater areas during the month of April. This paper describes methods for identifying times, locations, and other circumstances that are associated with maximal predation rates upon certain taxa. The information gained from these approaches can be used to inform management strategies, with the goal of reducing effects of predation on specific organisms. Virginia Department of Game and Inland Fisheries through a Sport Fish Restoration Grant from the U.S. Fish and Wildlife Service [2012-13705]; Virginia Sea Grant [R/71856A] We thank C. Hilling, B. Peoples, J. Emmel, Z. Moran, J. Woodward, A. Mosely, H. Kim, H. Lee, B. Greenlee, J. Odenkirk, R. Willis, K. Johnson, A. Weaver, Y. Jiao, and S. Smith for their assistance over the course of the study. We thank the anonymous reviewers whose comments resulted in a better manuscript. Data collection was supported by the Virginia Department of Game and Inland Fisheries through a Sport Fish Restoration Grant from the U.S. Fish and Wildlife Service (contract #2012-13705), and the senior author was partially supported through a fellowship from Virginia Sea Grant (R/71856A). Public domain – authored by a U.S. government employee

Given its ubiquity, it is not surprising that agriculture, including finfish aquaculture, contributes to food webs worldwide and is used by numerous wildlife for foraging and meeting other needs. Double-crested Cormorants (Phalacrocorax auritus) impact United States commercial aquaculture and are considered the primary avian predator in catfish (Ictalurus spp.) aquaculture facilities in the Mississippi Delta. Recent changes in aquaculture practices, regulatory policies, and decreased overall hectares in production prompted this study that assessed cormorant consumption of catfish in relation to their night roosts through surveys and diet analysis. Cormorants were collected from night roosts from October through April 2016–2018 (n = 69 collections). On average, catfish constituted 33% of a cormorant's overall diet, which is less than reported in previous studies. There was no statistical difference between consumption of channel (I. punctatus) and hybrid catfish (I. punctatus x I. furcatus) based on biomass estimates, and the greatest consumption of catfish occurred in the months of February and March. The best fit model for predicting catfish consumption was the cubic polynomial function of the area of catfish aquaculture within a 30.6 km forage buffer of a night roost. Our findings will inform wildlife managers about relationships between cormorant night roost locations and consumption of catfish and aid decision making with respect to cormorant management. Despite cormorants having shifted consumption to naturally occurring fish species associated with changes to aquaculture, aquaculture remains an important part of regional food webs.

El bagre de canal (Ictalurus punctatus) es uno de los peces endémicos de Norte América con mayor potencial para la acuicultura. A pesar de esto, los datos sobre su distribución actual son escasos y se desconocen muchos aspectos de su dinámica y desempeño productivo. En el presente estudio se reportan los resultados de una búsqueda bibliográfica y análisis de campo que permiten describir la situación actual del bagre de canal con respecto a su distribución geográfica histórica y actual, así como de la problemática que enfrentan los sistemas productivos de esta especie en México. Se identificó la falta de información e indicadores que permitan conocer la extensión de su hábitat natural, movilización o potencial productivo. La calidad y disponibilidad del agua figuran entre las principales problemáticas de la industria; el alimento supone el mayor gasto para los productores y existe gran heterogeneidad de manejo tanto en granjas reproductoras como de engorde, gran parte de la dinámica productiva sigue un modelo de ensayo y error. Se requiere optimizar y homologar los procesos del sistema productivo de bagre de canal, así como caracterizar correctamente las poblaciones domésticas y silvestres para aprovechar al máximo su potencial. Channel catfish (Ictalurus punctatus) is one of the endemic fishes of North America with the greatest potential for aquaculture. Despite this, data of its current distribution is scare and many aspects of its dynamic and productive performance remain unknown. In the present study, results are reported from a literature search and field analysis for describing the current status of channel catfish in Mexico regarding its historical and current geographical distribution as well as the problems faced by fish farmers and production systems. We were able to identify a lack of information and indicators to properly assess the extent of the species natural habitat and its productive potential. The quality and availability of water are among the main problems of the industry. Food costs represent the larger cost-loss for producers and there is great heterogeneity on the management of both breeding and production farms. Much of the production dynamics follows a pattern of trial and error. It became clear the need to optimize and standardize the processes on the channel catfish production system and to properly characterize domestic and wild populations to maximize their potential.

Production variables of hybrid catfish (Channel Catfish Ictalurus punctatus × Blue Catfish I. furcatus) reared in nursery ponds and then stocked were compared between fish fed immediately after stocking (standard industry practice) and fish for which feeding was postponed after stocking. Ponds (0.04 ha) were stocked with swim-up fry at 10,000 fish/pond (250,000 fish/ha). At 2 weeks poststocking, fish in the postponed feeding treatment were significantly smaller than fish in the standard feeding protocol. Therefore, all ponds began receiving commercial diets after 2 weeks. At 2 weeks poststocking and continuing through 5 weeks poststocking, the average individual fish length and weight was greater for the standard feeding protocol than for the postponed feeding protocol. At harvest, there were no differences in production variables between the two feeding protocols. Unlike a previous study with Channel Catfish fry, where feed was withheld for 6 weeks without compromising production, noticeable defi...

Tandem hoop nets have become the primary gear for sampling channel catfish Ictalurus punctatus, but suffer from high incidences of bycatch, particularly aquatic turtles that usually drown as a result. We sought to determine if bait type, ZOTE© soap and ground cheese logs, would influence catch of channel catfish (CPUE and mean TL) and bycatch of fishes and aquatic turtles. We sampled with tandem hoop nets in 13 Kentucky reservoirs (5–73 ha) using a crossover design and two sampling events. We found no difference in channel catfish catch rates between bait types, but mean sizes of fish caught using ZOTE© soap were approximately 24 mm longer compared to cheese. Fish bycatch was similar between bait types, but tandem hoop nets baited with ZOTE© soap caught up to 61% fewer turtles and mortality of turtles that were captured was up to 12% lower than those baited with cheese. Depth of net set, water temperature, and Secchi depth were environmental factors measured that affected catch and bycatch, but varied among species. Using ZOTE© soap as bait in tandem hoop nets appears to be a fairly simple and straightforward method for maintaining high catch rates of channel catfish while minimizing turtle mortality.

The American Fisheries Society (AFS) has recommended standard gears and methods for collecting North American freshwater fish data, but selectivity of these gears, including gill nets, is poorly described for most species. We calculated contact selectivity for species commonly collected with AFS standard gill nets in lakes and reservoirs of North America, including Black Bullhead Ameiurus melas, Channel Catfish Ictalurus punctatus, Walleye Sander vitreus, and Yellow Perch Perca flavescens. The normal selectivity curve provided the best fit to empirical catch data for all species. Inclusion of a tangle factor improved model fit for Black Bullhead, Channel Catfish, and Walleye, indicating that tangling is an important means of capture for these species. Channel Catfish were more susceptible to tangling than the closely related Black Bullhead, likely because larger Channel Catfish are more vulnerable to tangling by spines in the smallest meshes, whereas Black Bullhead in the same meshes were wedged. ...

This 210-day study compared variation in water quality and fish growth for channel catfish (Ictalurus punctatus; 47 g/fish) stocked in earthen ponds (1.5 fish/m2, 14,820/ha) and in a biofloc technology (BFT) production system with high-density polyethylene-lined rectangular tanks (12.6 fish/m2, 126,000/ha). Feed input and culture environment affected water-quality dynamics. In ponds, phytoplankton uptake predominated and little nitrification occurred, whereas in the BFT system phytoplankton uptake and nitrification maintained low ammonia-nitrogen concentrations. Size classes of fish were skewed toward the larger market sizes in ponds and toward smaller market sizes in the BFT system. Mean final fish weight was 630 g/fish in ponds and 542 g/fish in the BFT system. Despite these differences, fish yield was higher in the BFT system (7.7 kg/m3 v. 1.5 kg/m3) because of the greater initial stocking rate.

Native to the central USA, the Blue Catfish Ictalurus furcatus and the Flathead Catfish Pylodictis olivaris have been widely introduced into many Atlantic slope rivers and are now found in several drainages of the Chesapeake Bay. Fisheries managers are concerned that these large, long-lived catfish species may be contributing to observed declines in anadromous species, such as the American Shad Alosa sapidissima, Blueback Herring A. aestivalis, and Alewife A. pseudoharengus, all of which once comprised major U.S. fisheries. We assessed spatiotemporal variability and selectivity in the diets of Blue Catfish and Flathead Catfish during the spawning migration of these alosines. Catfish stomachs were collected during March–May in nontidal freshwater, tidal freshwater, oligohaline, and mesohaline portions of the James River. Diet contents were extracted from 2,495 catfish, 69.86% of which had prey items present in their foreguts (N = 1,743). We used DNA barcoding to identify degraded fish prey; nearly ...

Blue Catfish Ictalurus furcatus were purposefully introduced into freshwater tributaries to Chesapeake Bay in the past, and populations have subsequently spread to new areas, negatively impacting native communities and causing concern for resource managers. To aid development of management strategies, we implemented a multiyear (2012–2015) tagging study of invasive Blue Catfish in a 40-km stretch of the Potomac River to estimate survival and assess movement patterns. Blue Catfish (N = 1,237) were captured by electrofishing and double-tagged to allow us to estimate tag retention rates; we used reward tags to increase reporting rates. Recaptured fish (N = 104; 8.4% return rate) were at large for between 2 and 1,208 d. Tag retention rates were 0.88 (SE = 0.045) after 1 year and declined to 0.31 (SE = 0.107) after 2.7 years. The mean minimum distance moved by fish was 24.1 km (range = 0.0–112.6 km). Most (63%) fish displayed downriver movements, but distance moved was unrelated to fish size or days at...

Hybrid catfish (female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus) have quickly become a major contributor to ictalurid catfish aquaculture in the United States. Hybrid catfish have unique production characteristics compared with Channel Catfish, and rapid adoption of the hybrid by fish farmers has outpaced research on appropriate management practices. This study was conducted to determine the effect of midsummer partial harvest of faster-growing fish on production characteristics in ponds with hybrid catfish in single-batch culture. Twelve 1.0-acre ponds were stocked with 10,000 year-class 1 hybrid catfish (~0.12 lb/fish) in mid-March 2015. In August 2015, six random ponds were partially harvested to remove fish larger than ~1.25 lb using an in-pond, flexible-panel, grading sock. In October 2015, all ponds were completely harvested. Partial harvest of faster-growing fish removed ~26% of fish from ponds in August. Removal of faster-growing fish resulted in 0.9% of the tota...

Global averages were obtained for amounts of energy, land, water, wildfish, nitrogen, and phosphorus embodied in aquaculture feed ingredients. These data allowed amounts of these embodied resources to be calculated for typical feed formulations for channel catfish, Ictalurus punctatus; hybrid catfish, I. punctatus♀ × I. furcatus♂; Vietnamese catfish, Pangasius spp.; Atlantic salmon, Salmo salar; rainbow trout, Oncorhynchus mykiss; tilapia, Oreochromis spp.; whiteleg shrimp, Litopenaeus vannamei; and black tiger shrimp, Penaeus monodon. Embodied resource use per m.t. of feed varied among species: energy, 4.90–12.48 GJ/m.t.; land, 0.082–0.312 ha/m.t.; water, 502–1227 m3/m.t.; wildfish, 0–2880 kg/m.t.; nitrogen, 3.08–8.63 kg/m.t.; phosphorus, 1.16–5.62 kg/m.t. These calculations did not account for variations in site-specific factors related to embodied resources and feed composition and use. But they suggest that reducing feed conversion ratio (FCR) by 0.1 unit for the seven species (species groups) could potentially reduce feed use by around 1.1 million tonne (Mt) while conserving 9.8 million GJ of energy, 270,000 ha of agricultural land, 1.4 billion m3 of freshwater, and 1.24 Mt of wildfish. Reduction of the FCR is a powerful means of lessening farm-level production costs and negative impacts of feed production and use.

Management 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. ...

In numerous avian species, egg size is correlated to female body condition, hatchling size and nestling growth. Recent demography studies of Interior Double-crested Cormorants (Phalacrocorax auritus) suggest a migratory divide across the Great Lakes; western populations winter in the Gulf of Mexico region of the southeastern United States (Alabama, Arkansas, Louisiana, and Mississippi) with extensive catfish (Ictalurus punctatus) aquaculture, and eastern populations winter in Florida, where catfish aquaculture is not pervasive. If Double-crested Cormorants have improved their overall body condition through catfish exploitation, then egg and chick sizes should also be affected. Three breeding areas in Ontario (east, central, and west) were selected for empirical measures of size variation. During the breeding seasons of 2006 and 2007, egg, naked young, fledgling, and adult morphometric data were collected. Eggs in eastern areas (volume = 465.8 ± 3.9 cm³) were on average larger than eggs in centra...

Habitat management is a crucial aspect of fisheries management. Without knowledge of habitat associations, fisheries scientists are unable to effectively make habitat conservation or restoration recommendations. This becomes especially prominent when trying to manage commercially harvested populations and protect threatened or endangered species. To determine juvenile fishes habitat associations in the Middle Mississippi River, we analysed mini-trawl catch data of six common juvenile fish species: blue catfish (Ictalurus furcatus), channel catfish (Ictalurus punctatus), channel shiner (Notropis wickliffi), freshwater drum (Aplodinotus grunniens), paddlefish (Polyodon spathula), and shovelnose sturgeon (Scaphirhynchus platorynchus). Overall, we conducted 2251 mini-trawl sampling efforts between 2002 and 2013, resulting in the capture of 23,742 target specimens. Catch per unit effort was evaluated by structural habitat (i.e. velocity, depth, and substrate). Overall, these data suggest that juvenile fish species are more prevalent in shallow water and slower velocities. Ultimately the information garnered during this evaluation should be incorporated when considering habitat modifications, especially those modifications that impact the availability of shallow-low velocity habitats. Copyright © 2016 John Wiley & Sons, Ltd.

In the southeastern USA, catfish aquaculture is burdened by predation from piscivorous birds and the digenetic trematodes they carry. In addition to cultured ictalurid fish, other forage or incidental fish species inhabit catfish production ponds. Of these, the inland silverside Menidia beryllina was recently found to harbor larval metacercariae of several trematode species. Three species of metacercariae were reported, two of which represent the first morphological descriptions of an Austrodiplostomum sp. and Bolbophorus sp. metacercaria, respectively. A total of 15 silversides were collected from a commercial catfish pond and examined for trematode infection. These fish were parasitized by metacercariae of an Austrodiplostomum sp. (100 % prevalence) in the eyes and brain, a Bolbophorus sp. (86.7 % prevalence) in the musculature, and Clinostomum marginatum (33.3 % prevalence) in the musculature and fins. All three trematode species were characterized morphologically and molecularly by sequencing of the cytochrome c oxidase subunit 1 gene (CO1). In addition, the internal transcribed spacer 1 region (ITS1), 5.8S rRNA gene, and ITS2 region were determined for the Bolbophorus sp., which linked this metacercaria to a Bolbophorus sp. cercaria from a planorbid snail Planorbella trivolvis and an unnamed Bolbophorus sp. adult from the American white pelican Pelecanus erythrorhynchos. Furthermore, Biomphalaria havanensis snails were collected from the same pond and found actively shedding cercariae morphologically and molecularly consistent with a diplostomid cercaria reported from Bi . havanensis in catfish ponds in Mississippi, USA. Sequence comparisons deemed these cercariae conspecific to the Austrodiplostomum sp. from inland silverside described here. Channel catfish fingerlings were exposed to these cercariae at doses of 50 and 100 cercariae per fish. The infectivity of this Austrodiplostomum sp. in channel catfish was assessed at 10 and 20 days post exposure (dpe). Metacercariae were observed in both the eyes and brain of infected channel catfish, supporting molecular data that suggests the cercaria and metacercaria are both stages of a previously unidentified Austrodiplostomum sp. life cycle.

A 2 × 2 factorial experiment was conducted to examine the growth performance of pond-raised hybrid catfish (female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus) fingerlings fed diets containing two levels of protein (35% or 32%) with two animal protein sources (fish meal or porcine meat, bone, and blood meal [PMBB]). Small hybrid catfish fingerlings with a mean initial weight of 2.0 g/fish (SD = 0.6) were stocked into 20 earthen ponds (0.04 ha) at a density of approximately 172,970 fish/ha, based on a sample count of 1,000 fish. The fish were fed once daily to apparent satiation for 113 d. Total weight of feed fed, gross yield, feed conversion ratio (FCR), condition factor, and observed mortality were not significantly affected by either dietary protein concentration or animal protein source. Results demonstrate that dietary protein levels can be reduced from 35% to 32% without compromising fish growth and FCR for hybrid catfish fingerlings raised from 2 to 71 g in a growing...

This study examined the influence of strain of sire on hybrid catfish embryo production and performance of fingerlings under commercial conditions. Four hundred 4-year-old female Gold Kist strain Channel Catfish Ictalurus punctatus were induced to spawn in eight spawning trials. The stripped eggs were fertilized with the sperm of either D&B or Rio Grande Blue Catfish I. furcatus to produce D&B or Rio Grande hybrid catfish embryos. Testes weight (g/kg body weight [BW]) was higher in Rio Grande (1.98 ± 0.28 g/kg BW) than in D&B (1.02 ± 0.12 g/kg BW) Blue Catfish males. Hatching parameters between Rio Grande and D&B hybrids did not differ. Approximately 100,000 hybrid catfish fry produced from each spawning trial were stocked in an individual 0.4-ha pond to raise fingerlings. Four ponds of D&B and four ponds of Rio Grande hybrids were stocked in eight ponds of identical conditions at the same time. The mean individual BW of D&B hybrid fingerlings (38.5 g) was higher than that of Rio Grande hybrid fin...

Off-flavor is a major challenge to the quality of farm-raised catfish fillet. In this work, headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS) was employed to analyze volatile compound profile of catfish fillet to find the volatiles which might be responsible for the off-flavor. Ten volatile compounds were identified, and their concentrations in on-flavor and musty off-flavor fillets were compared. The off-flavor fillet contained significant larger amount of geosmin (GSM), 2-methylisoborneol (MIB), hexanal, 1-octen-3-ol and nonanal, indicating they might be related to the musty off-flavor. Sensory evaluation of the five compounds and their combinations suggested that GSM and MIB might be mainly responsible for the musty off-flavor, while the presence of hexanal or 1-octen-3-ol might notably intensify the off-flavor. This research suggested that besides GSM and MIB, some small aldehydes and/or alcohols might also need to be considered for controlling off-flavor in catfish fillet. This work also provided a useful chemistry-based objective method to evaluate the effects of treatments and/or managements in reducing catfish off-flavor.