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Transcriptome profiles of albino and wild type catfish were generated using next generation high-throughput RNA sequencing technology and compared. A total of 1106 differentially expressed genes were obtained, of which 530 were up-regulated and 576 were down-regulated in the skin tissue of albino catfish relative to wild type catfish. In total, 30,813 alternative splicing (AS) events were identified. These AS events were distributed in 15,090 genes with an average of 2.04 AS events per gene. We identified and compared a large proportion of transcripts encoding genes involved in regulation of melanogenesis, melanosome biogenesis, melanosome transport, and the tyrosine metabolism pathway in the catfish skin transcriptome dataset. Further analysis revealed that differentially expressed genes, including MART1, Cdk2, PMEL17, Tyr, Tyrp1, ADH, HGD, and TYRL, were significantly overrepresented in the melanogenesis pathway and in several biological processes associated with pigmentation. The albino catfish skin samples exhibited significantly increased expression levels of all candidate genes in the tyrosine metabolism pathway. We also identified a possible mechanism for the mutation of the catfish Hps4 gene, which affects regulation of expression of genes in the tyrosine metabolism pathway. Our findings provide a theoretical basis for further understanding of the pathogenesis of albinism in catfish.

Antibiotics are frequently used in feed to control bacterial diseases in aquaculture settings. In addition to the intended purpose of controlling diseases, applications of medicated feed may significantly change the composition of the gut microbiota, which in turn may have impact on host-pathogen interactions. However, nothing is known concerning the effects of antibiotics on microbiota in the gut channel catfish (Ictalurus punctatus), the most important aquaculture species in the United States. In this study, we determined the impact of medicated feed containing florfenicol on microbiota in the gut of catfish at various times post-feeding. Through analysis of bacterial 16S rRNA gene amplicons, we found that the medicated feed had a dramatic impact on the composition of the gut microbiota, with significant enrichment of Plesiomonas spp., accounting for 66% of all gut bacteria. Along with other related species, Proteobacteria taxa accounted for 93% of all microbiota by day 10; in contrast, the gut microbiota of fish receiving non-medicated feed harbored a bacterial assemblage that had greater ribotype richness and a more even distribution (P

This study quantified the effects of pond rearing environments on microbial community composition in larval channel catfish (Ictalurus punctatus) gastrointestinal (GI) tracts across early developmental stages. Larvae were reared under standard industry conditions and sampled at five developmental stages (Egg, Swim-up, Day of stocking, 24 h post-stocking, and 21 d post-stocking). Massive-parallel sequencing of a segment of the 16S rRNA gene was conducted using an Illumina MiSeq platform to characterize the diversity and taxonomic composition of gut and water microbial communities. PERMANOVA analyses of differences in egg and gut microbial community composition across stages indicated a significant interaction between nursery pond environment, and family (P

Stocking density is one of the major factors affecting production and welfare of fish in aquaculture. This study investigated the effect of different stocking densities on growth, feed efficiency, blood biochemistry, histometric response, muscular composition, and flesh quality of channel catfish Ictalurus punctatus. Fish were cultured at low, medium, and high stocking density of 50, 150, and 300 fish m−3, respectively, for 60 days in the recirculating aquaculture system. Fish growth and feed efficiency significantly decreased with increasing stocking density. Serum concentrations of glucose, triglyceride, and total cholesterol, as well as the activities of both aspartate aminotransferase and alanine aminotransferase, significantly elevated as stocking density increased. High stocking density led to the decline in serum levels of thyroid hormones. The villi length and its number, as well as the size of goblet cells in the intestine, were negatively affected by high stocking density. There was a significant density-dependent decrease in muscular fat content, diameter of dorsal muscle fiber, intensity of muscular bundles, and percentage of muscular bundles area in dorsal muscle. However, the percentage of the intramuscular connective tissue showed a significant increase in fish reared at high stocking density. Fish stocked in high density exhibited the decrease in muscle pH, drip loss, and frozen leakage rate. Overall, the increased stocking density could cause the unfavorable impacts on growth, feed efficiency, histological change, and flesh quality of I. punctatus.

As the ethanol industry matures and adopts new technologies, the co-products produced are also changing with their composition adjusted to meet feed industry needs. High protein distillers dried grain with yeast (HP40Y) is a relatively new product which is a variant of distillers dried grains that could be used as an improved protein source in catfish feed formulations. To evaluate the efficacy of HP40Y, a 10-weeks growth trial was conducted on the growth performance of juvenile catfish, Ictalurus punctatus (mean initial weight 1.80 ± 0.05 g). In the growth trial, graded levels of HP40Y (0.00, 3.10, 6.20 and 9.30%) were used to replace poultry meal (PM: 6.0, 4.0, 2.0 and 0.0%) and other series of diets were used with HP40Y (5.0, 10.0, 15.0, 20.0, 30.0 and 40.0%) to replace soybean meal (SBM: 51.00, 46.49, 41.90, 37.40, 28.20, 19.20%). Analysis of Covariance (ANCOVA) indicated a significant interaction between replaced protein (PM and SBM) and the inclusion level of HP40Y (up to 20%) on biomass, mean final weight, weight gain, and FCR (P

Channel catfish (Ictalurus punctatus) is an important aquaculture species worldwide. Although studies of the sex determination mechanism of channel catfish began during the 1980s, the mechanism and sex-specific genes remain unclear. In this study, based on the results of sex-related quantitative trait locus (QTL) mapping and targeted next-generation sequencing (NGS) technique, 13 male-specific single nuclear polymorphisms (SNPs) were identified in the coding region of the zbtb38 gene of channel catfish by targeted next-generation sequencing. Among them, six substitutions resulted in changes in the amino acid coding in zbtb38 on both the X and Y chromosomes. It is speculated that zbtb38 on the Y chromosome has an important role in testicular differentiation and is an important candidate gene for sex determination in channel catfish. Subsequently, male-specific primers were designed according to male-specific nucleotides, which amplified an expected band from males but not from females. Thus, a rapid and effective method was successfully established to identify the genetic sex of channel catfish. Our study contributes to the study of the sex determination mechanisms and development of mono-sex populations in channel catfish.

An emerging pathotype of Aeromonas hydrophila (vAh) has been responsible for widespread farm losses in the US catfish industry over the last decade. While our genetic and biochemical understanding of vAh has been greatly enhanced in this time frame, our ability to reliably induce the disease in the laboratory has remained limited. Taking cues from observed farm conditions associated with outbreaks, here we perturbed iron scavenging dynamics and catfish feeding status. Addition of a xenosiderophore, deferoxamine mesylate (DFO), to vAh cultures prior to immersion challenge significantly increased virulence in several vAh isolates but not in a non-epidemic strain. DFO addition did not impact vAh growth dynamics or perturb iron-sensitive gene pathways, but did significantly enhance hemolysis of catfish blood. Furthermore, hours between last feeding and immersion challenge (postprandial status), was observed to be a critical determinant of catfish susceptibility. Fish with a full gastrointestinal tract had significantly lower survival than those in a fasted state, and this effect was cumulative with that of DFO-enhanced vAh virulence. Taken together, our results not only provide a more robust challenge model, they offer actionable insights into pond level host-pathogen-environmental interactions potentially underlying vAh pathogenesis.

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.

The live transport of juvenile channel catfish (Ictalurus punctatus) is an important part of channel catfish breeding in China, but the anesthetic dose and physiological response of channel catfish after transport have not been studied yet. The purpose of this study was to assess the potential of eugenol and thymol in live transport and study their anesthetic effects of on juvenile channel catfish by analyzing a large number of parameters associated with stress and nonspecific immunity. First we tested eugenol and thymol concentrations of 10, 20, 30, 40, 50, and 100 mg/L. Eugenol successfully anesthetized the experimental fish at concentrations of 30–100 mg/L for 1258–82 s (resuscitation time was 147–300 s), while thymol was effective at 20–100 mg/L for 1612–81 s (recovery time was 333–475 s). The second experiment involved adding 10 and 20 mg/L of eugenol and thymol (4 groups) to the water, simulating transport (5 h), analyzing the stress and non-specific immune parameters of the serum, and determining gene expression changes in the liver and head kidney for 48 h. Anesthetics in the transport water inhibited the increase in serum cortisol levels (treatment group: 39.81–60.79 ng/mL, control group: 142.14 ng/mL), and Hsp90 in the liver was a more suitable biomarker for transport stress in channel catfish than Hsp70. Concentrations of serum total Ig, lysozyme, lectin, and ACH50, as well as the expression levels of cytokines (IL-1β, IL-8, and TNF-α) and pattern recognition receptors (NOD-1) in the head kidney increased. The expression of cytokines and NOD-1 in the head kidney returned to the pre-transport level after 48 h. Both anesthetics are suitable for channel catfish, but thymol is more suitable as a transport sedative. The results of this study could help maintain the health of juvenile channel catfish after live transport, decrease their infection and mortality, improve wellbeing, and reduce economic losses to the aquaculture industry.

Constructs bearing growth hormone (GH) cDNA from channel catfish, Ictalurus punctatus, driven by the ocean pout, Zoarces americanus, antifreeze protein promoter (opAFP), or by the rainbow trout, Oncorhynchus mykiss, metallothionein promoter (rtMT) were transferred to channel catfish via electroporation. Transgenic P1 individuals were mated to produce F1 individuals that exhibited enhanced growth rate. The inheritance of the transgene by the F1 generation was 10% to 36%. The mean body sizes of F1 transgenic fish were larger than their non-transgenic full-siblings (P 0.05) between transgenic and non-transgenic full-siblings except for one opAFP-ccGH family, although the observed means were smaller for four of six transgenic groups as apparently their relative length was increasing more rapidly than relative weight compared to their respective controls. Examining the data from the current experiment and that from an earlier experiment with the same genetic types, but grown to a smaller size, it appears that the two promoters gave similar results in regards to growth enhancement. The largest individuals were always in the transgenic families, and this along with the family effects suggest that gene transfer coupled with combined individual and family selection might result in larger fish than the GH transgenesis alone. The growth enhancement in the current experiment was better than previous experiments with channel catfish that used RSV-LTR-salmonid GH constructs. Assuming government approval and the same growth to food size, GH transgenic channel catfish would increase farm income by $3421/ha compared to use of non-transgenic channel catfish.

In 1984, channel catfish (Ictalurus punctatus) was introduced to China from the US. Because of its desirable traits for commercial production, the cultivation area and total production of channel catfish increased in China, reaching a production of 248,000 metric tons and generating an export income of more than 50 million US dollars in 2014. Along with the US, China has become a major producer and consumer of channel catfish. In August 2003, the US Department of Commerce imposed an antidumping tariff on frozen Pangasius fillets from Vietnam, which provided a good opportunity for export of China channel catfish. But since then both export volume and value had been choppy and volatile. Meanwhile, from 2003 to 2012, the prices of domestic market were largely affected by exports. Export volume and value in the previous year influenced the domestic market prices in the next year. Because of the sharply declined export in 2007, attention was focused on the domestic market. After 2009, the domestic market consumption gradually expanded from 60% to more than 85%. Stability of the domestic market resulted in reduced price fluctuations in the domestic catfish prices and a slowly upturn of exports. This review outlines the historical, present situation and challenges of the channel catfish industry in China and provides some suggestions for its sustainable development.

The study was conducted using channel catfish and tilapia to evaluate the production performance of these fish to increasing levels of lysine from crystalline and intact lysine supplemented in practical diets. A practical lysine deficient basal diet was developed using corn protein concentrate (Empyreal® 75) as a primary protein source. To this diet either graded levels of crystalline lysine or similar levels from a high lysine corn protein concentrate (Lysto™) were added. In the channel catfish trial, the first five diets were designed to contain increasing levels of crystalline lysine (1.21%, 1.34%, 1.45%, 1.56%, and 1.72%) with an additional four diets using intact protein from a high lysine corn protein concentrate (1.40%, 1.57%, 1.77%, and 1.91% lysine). In the tilapia trial, lysine from two sources was added to 11 diets to produce analyzed lysine levels of 0.92%, 1.11%, 1.23%, 1.34%, 1.54% 1.65% in the first six diets using crystalline lysine and 1.13%, 1.38%, 1.61%, 1.81%, 2.02% in the last five diets using intact lysine. Results indicated that channel catfish and tilapia have positive performance with increasing lysine supplementation up to the requirement. Fish fed with the higher levels of lysine had the highest weight gain and lowest feed conversion ratio. The regression analysis on the increased level of inclusion of crystalline lysine and intact lysine showed no significant difference in slope. Based on the growth, feed conversion ratio and apparent net protein retention data obtained from this study, it can be concluded that the effectiveness of using intact lysine via high lysine corn protein concentrate as a lysine supplement is not significantly different from crystalline lysine. Thus, the high lysine corn protein concentrate is a feasible ingredient for aquaculture feeds, which can be used to balance the amino acid composition of the diet without addition of crystalline lysine. Statement of relevance Present study shows that high lysine corn protein concentrate is a feasible ingredient for aquaculture feeds, which can be used to balance the amino acid composition of the diet without addition of crystalline lysine.

Organisms exposed to sub-zero temperatures are at risk of freezing damage. Fingerling channel catfish, Ictalurus punctatus , hybrid catfish (channel catfish female × blue catfish, Ictalurus furcatus , male), channel catfish transgenic for the goldfish glutamate decarboxylase 65 gene driven by the carp β-actin promoter (βA-GAD65), and channel catfish transgenic for the catfish growth hormone gene driven by the antifreeze protein promoter (AFP-ccGH) were compared for survival at different temperatures (9.0 °C, 6.0 °C, 3.0 °C, 1.0 °C, 0.5 °C, 0 °C, and − 0.5 °C) at different salinities (0 ppt, 2.5 ppt, 5 ppt, and 7.5 ppt). The two transgenes were of interest as growth hormone not only affects growth, but also affects osmoregulation, and GAD65 construct could alter gonadotropin with the potential consequence that GnRH affects growth hormone production. Survival was 98–100% for all genetic groups at all salinities between 0 °C and 9.0 °C. However, large differences were observed at − 0.5 °C. At 0 ppt salinity, 100% of AFP-ccGH transgenic (T) fingerlings survived, but survival of all other genetic groups was 0–2%. Raising salinity to 2.5 ppt at sub-zero temperature had a strong positive impact on survival as survival rates of AFP-ccGH (T), AFP-ccGH control (C), channel catfish, βA-GAD65 (T), βA-GAD65 (C) and hybrid catfish were 100, 100, 98, 76, 100 and 18%, respectively. Increasing salinity further to 5 ppt decreased overall survival, although it was still higher than at 0 ppt. Survival rankings were altered, with means for βA-GAD65 (T), βA-GAD65 (C), AFP-ccGH (T), AFP-ccGH (C), channel catfish and hybrid catfish of 69, 0, 15, 22, 0 and 0%, respectively. Mortality was 100% in all genetic groups at − 0.5 °C and 7.5 ppt demonstrating significant interaction between temperature and salinity. Negative heterosis was observed for the hybrids at low temperature at the respective salinities. Statement of relevance We believe that this topic has not been previously addressed. These pleiotropic effects have never been described in GH transgenic or GAD transgenic fish and have relevance for aquaculture/natural resource management for future climate change as well as management and genetic management today. It is the first paper to evaluate the survival of hybrids under freezing, very important for countries that are suffering from freezing weather.

The enteric septicemia of channel catfish, caused by Edwardsiella ictaluri, is one of the most severe diseases in channel catfish worldwide. Currently, a safe and highly effective vaccine is urgently needed for the control of this disease. In this study, E. ictaluri ghosts (EIGs) were first generated by PhiX174 lysis gene E, and the hematological indices and relative percent of survival (RPS) were examined in channel catfish (Ictalurus punctatus) after immunization. Generation of ghosts in the transformant of E. ictaluri carrying the plasmid pBV-lysisE was enhanced by increasing the incubation temperature up to 42 °C. Lysis of E. ictaluri occurred 2 h after induction and the process was complete in 6 h. The efficiency of ghost induction in non-lyophilized E. ictaluri was 99.997%. Additionally, no bacterial growth was detected by culture on BHI plates after lyophilization of the ghosts. The immune response of channel catfish immunized with the E. ictaluri ghosts indicated that the number of erythrocytes and leucocytes reached a maximum value of 3.53 × 106 and 5.25 × 105 cell/ml, at day 4 post-immunization, respectively, which were both significantly higher than in the control group inoculated with PBS only (P Statement of relevance In the paper, we illustrated the generation method of Edwardsiella ictaluri ghosts and the immunological responses and protection in channel catfish after being immunized with E. ictaluri ghosts. The result of this paper indicated that E. ictaluri ghosts would be an effective approach for preventing ESC in channel catfish in the future.

Commercial channel catfish (Ictalurus punctatus) is an economically valuable agricultural commodity in the United States, which suffers heavily from bacterial pathogens including Edwardsiella ictaluri. Our previous study revealed that dietary trans-cinnamaldehyde (TC) reduces catfish mortality after E. ictaluri infection, but there is limited knowledge of the effect of TC on the antioxidant defense system in catfish. In this study, we aimed to investigate the response of the catfish antioxidant defense system following TC feeding as well as E. ictaluri infection. In the first experiment, catfish fingerlings were fed with a basal diet or a basal diet supplemented with TC (20 mg/kg diet) for 10 days, and the level of five oxidative stress biomarkers were measured in the hepatic tissue. Compared with the control group, superoxide dismutase (SOD) activity was increased significantly and the malondialdehyde (MDA) concentration decreased significantly (P

Long-term storage of spermatogonial stem cells (SSCs) represents the next step for advancing aquaculture research by providing valuable genetic resources for genetic enhancement programs and xenogenesis technologies. Hybrid catfish, the cross between channel catfish, Ictalurus punctatus ♀ and blue catfish, I. furcatus ♂, are in high demand by the US aquaculture industry, but production can be limited by the availability of blue catfish gametes. Therefore, xenogeneic stem cell transplantation is a powerful method for generating blue catfish gametes within faster growing and maturing channel catfish hosts. These technologies could be facilitated by having cryopreserved SSCs from testicular tissue on-hand in gene banks. Cryopreservation protocols for blue catfish testicular tissues and for other fish species are still being optimized, and currently, data is lacking on the effects antioxidants and antifreeze proteins (AFPs) have on cellular post-thaw viability of SSCs. The objective of this study was to analyze the individual and combined effects of antioxidants (catalase, hypotaurine, and ascorbic acid) and AFPs (I and III) on post-thaw type A spermatogonia cell production and viability from testicular tissue. In this study, there were no improvements with individual antioxidant or AFP treatments. However, when the antioxidants hypotaurine and catalase were tested in combination with different AFPs, three treatments had higher type A spermatogonia cell production than the control, including hypotaurine 7 mM + AFPI 1 μg/mL, hypotaurine 3.5 mM + AFPI 0.1 μg/mL, and hypotaurine 7 mM + AFPIII 0.1 μg/mL. These treatments along with hypotaurine 7 mM + AFPI 0.1 μg/mL and catalase 100 IU + AFPI 0.1 μg/mL had higher viability than the control. From these results, we recommend adding these antioxidant-AFP combinations to future cryopreservation protocols. Overall, this is the first study showing that combining specific antioxidants and AFPs can improve spermatogonia cryopreservation for a fish species.

A strain of atypical Aeromonas hydrophila (aAh) has caused issues within the channel catfish Ictalurus punctatus industry of the southeastern United States since 2009. These atypical pathotypes cause acute mortality events resulting in catastrophic losses, as opposed to more chronic mortality and lesions seen in typical infections of motile aeromonas septicemia (MAS). This study provides a basic framework for rapid field sampling negating the need for re-isolation or enrichment culture, thereby reducing the time between sampling and detection. Rapid and accurate quantitative PCR based methods for detection of aAh have been described and are important confirmative tools in research and diagnostic settings. These methods also have application in epidemiological surveys investigating the spread of disease and elucidating pathogen dynamics that may lead to outbreaks. To date, no field-based sampling technique for rapid aAh detection in resident pond populations has been explored. In this study, culture swabs taken from the gills and lower intestine of pond-raised catfish were assessed for their suitability as rapid field-based collection methods for downstream applications. Results showed the state of the pond has a significant effect on which swab location yields the highest proportion of PCR positive results. During an active outbreak, gill swabs identified more fish as aAh-positive; however, in apparently healthy populations, swabs taken from the lower intestine identified significantly more aAh-positive fish than gill swabs, despite no statistical difference in the concentration of aAh cell equivalents between swab sites. Naive prevalence estimates from the two swab types were compared to estimates provided by a hierarchical occupancy model. Prevalence estimates from gill swabs was 0.95% while vent swabs showed a prevalence of 2.2%; however, estimates based on the occupancy model were 6.6% and 9.8%, respectively. This multi-fold increase in prevalence estimates highlights the importance of accounting for imperfect detection in epidemiological studies and in assessing potential outbreak risk. Furthermore, occupancy models based on these data indicate resident fish can be aAh-positive carriers with no gross signs of infection, providing evidence aAh can reside in catfish ponds in the absence of disease. The presence of a carrier state indicates the pathogen may pose minimal risk to the host is compromised or a mechanical portal of entry into the blood stream is available. This provides an important direction for future research in understanding the mechanisms of aAh outbreaks in catfish aquaculture ponds.

Xenogenesis is emerging as an innovative technology for hybrid catfish (channel catfish, Ictalurus punctatus ♀ × blue catfish, I.furcatus ♂) production, where primordial germ cells (PGC), spermatogonial stem cells (SSCs) or oogonial stem cells (OSCs) are transplanted into infertile host species such as triploid fish to produce xenogens. Currently, donor cells are collected from randomly selected immature fish without having prior knowledge regarding the best donor stage, which is critical to increase the efficiency and success of germ cell transplantation in catfish breeding. Therefore, the current study was carried out with the objective of determining the relationships between quantity of stem cells, total length (TL), total weight (TW), and the level of androgens [testosterone (T) and 11-ketotestosterone (11-KT)] in blue catfish (donor fish). Positive quadratic relationships were observed between TL and the number of extracted live SSCs (r2 = 0.51; P

Hybrid catfish, the progeny of channel catfish (Ictalurus punctatus) females × blue catfish (I. furcatus) males, are in high demand by the United States aquaculture industry because they outcompete each of the parent species for pond and raceway culture. Unfortunately, fry production can be a limiting factor due to a lack of natural hybridization between the two species and the necessity to sacrifice males for artificial fertilization. Males are costly to maintain in hatcheries and take longer to mature than channel catfish males. Therefore, it is essential to use the minimum quantity of sperm that allows for the highest fry production. In this study, channel catfish eggs from 9 females were collected from two different locations and fertilized with six different sperm to egg ratios ranging from 1.0 × 103:1 to 1.0 × 105:1. Embryos were then incubated under common environmental conditions until hatch. Overall average hatch success ± SE using sperm to egg ratios between 1 × 103 and 1.0 × 105 ranged from 18.3 ± 4.3 to 48.8 ± 8.3%. Overall, there was a significant effect of sperm to egg ratio (P 1 × 104:1 sperm per egg had no significant improvement on hatch success. Both study locations indicated significant impacts of sperm to egg ratio (P

Lack of freshwater is emerging as the most critical natural resource issue facing humanity. Ongoing climate change will reduce freshwater supplies, and demand for food continues to expand rapidly. Swim-up channel catfish, Ictalurus punctatus, fry transgenic for the channel catfish growth hormone (GH) gene driven by the rainbow trout Oncorhynchus mykiss metallothionein promoter (rtMT-ccGH), or by the ocean pout Zoarces americanus antifreeze protein promoter (opAFP-ccGH), channel catfish, and albino channel catfish were grown at 0, 2.5, 5, and 7.5 parts per thousand (ppt) salinity. Survival was 100% for all genetic groups at 0 and 2.5 ppt. Increasing salinity to 5 ppt decreased overall survival as survival rates of rtMT-ccGH transgenic (T), rtMT-ccGH control (C), opAFP-ccGH transgenic (T), opAFP-ccGH control (C), channel catfish, and albino channel catfish were 83, 82, 83, 77, 89 and 40%, respectively. Increasing salinity to 7.5 ppt had a strong negative impact on survival as means for rtMT-ccGH (T), rtMT-ccGH (C), opAFP-ccGH (T), opAFP-ccGH (C), channel catfish, and albino channel catfish were 67, 13, 67, 10, 18, and 7%, respectively with the albino channel catfish having the lowest survival followed by opAFP-ccGH (C) (P = .002). Raising salinity to 2.5 ppt greatly increased the growth rate of GH transgenic channel catfish (11–33%), channel catfish (56%), and albino channel catfish (124%). NaCl had a negative effect on survival and growth rate for swim-up fry at 5 ppt. Significant differences were observed at varying salinity (P

Since excreted feed nitrogen is bio-transformed efficiently in a fully functional mixotrophic biofloc technology production system, re-using this biofloc water over multiple production cycles should be beneficial. The present study, conducted in an outdoor biofloc technology production system, evaluated impacts on fish production characteristics and mineral status, common microbial off-flavors, and water quality dynamics for channel catfish (Ictalurus punctatus) reared in one-year-old waters with low or high total suspended solids used previously for two consecutive catfish biofloc studies or in unused (new) water. Total suspended solids were maintained at 300 to 400 mg/L in the unused and low total suspended solids used water treatments and allowed to accumulate in the high total suspended solids used water treatment. Tanks (18.6 m2, 15.7 m3) were stocked with fingerlings (47.5 ± 0.8 g/fish) at 13.5 fish/m2 (16 fish/m3) and grown for 181 days. Channel catfish production characteristics did not differ significantly among treatments. Overall, gross fish yield averaged 10.2 kg/m3 and fish averaged 642 g/fish. Nitrate accumulation rate was affected by total suspended solids concentration with a significant reduction observed at the highest discharge of solids from the system, suggesting wash-out of nitrifiers. Treatment effects on water quality dynamics, macro- and trace-mineral status of water, feed, and fish, 2-methylisoborneol and geosmin off-flavors and associated phytoplankton populations also are discussed. Results of this study suggest that one-year-old biofloc water can be used without adverse impact for a second year of channel catfish production in the biofloc system.

Studies were conducted to determine aspects of water chemistry responsible for large differences in pathogenesis and mortality rates in experimental challenges of channel catfish Ictalurus punctatus with Flavobacterium columnare ; challenges were conducted in water supplying either the Stuttgart National Aquaculture Research Center (SNARC) in Stuttgart, Arkansas, or the Warmwater Aquaculture Research Unit (WARU) in Stoneville, Mississippi. Waters differed in two major characteristics: compared to SNARC water, WARU water contained appreciable dissolved organic matter (DOM) and very low concentrations of dissolved calcium and magnesium. In Experiment 1, fish were exposed to a bacterial challenge of F. columnare in aquaria with either SNARC or WARU water. Fish mortality at 4 d was 100% for fish in SNARC water, while no fish died in WARU water. Bacterial adhesion to gill surfaces also differed dramatically in the two waters and was approximately 1900-times higher for fish challenged in SNARC water (more than 800,000 bacterial CFUs/ng extracted DNA) than for fish challenged in WARU water (fewer than 450 CFUs/ng). Experiment 2 was conducted with a lower bacterial challenge to determine which factor, DOM or divalent cation concentration, caused the difference in mortality seen in Experiment 1. Complete removal of DOM from WARU water by carbon filtration did not affect bacterial adhesion to gills nor resulted in greater mortality in challenged fish. Consequently, DOM did not contribute to the differences in mortality seen in Experiment 1. However, removal of most calcium and magnesium from SNARC water by ion-exchange filtration resulted in decreased bacterial adhesion to gill and decreased mortality compared to un-altered SNARC water. It appears that the concentration of divalent cations (hardness) affects the pathogenesis of columnaris disease.

A population of channel catfish (Ictalurus punctatus), referred to as the Delta Selects, was established in 2006 and has been selected for increased growth and carcass yield as part of the USDA's Warmwater Aquaculture Unit's mission to develop improved catfish germplasm for release to U.S. catfish farmers. The base population was established from catfish collected from 10 commercial farms. Broodfish were spawned in ponds, full-sib families were reared in separate tanks until tagging at 8 to 10 months post-hatch, then fish were reared communally in earthen ponds until 16 to 18 months post-hatch. Fingerling weight, harvest weight and sex were recorded. A sample of males and females from each full-sib family was processed and carcass weight (head and viscera removed) was recorded. Pedigree was determined by assigning offspring to parents based on inheritance of microsatellite alleles. Data was collected on offspring produced in 2008, 2009, 2011, 2012, 2014 and 2015. Various statistical models were compared, and variance components and breeding values were estimated with BLUP F90 software. Selection was based on estimated breeding values for increased harvest weight and carcass yield. Fingerling weight was recorded for 27,000 fish from 945 full-sib families produced by 465 sires and 726 dams; harvest weight was recorded for 27,160 progeny from 954 full-sib families produced by 467 sires and 731 dams; and carcass weight was recorded for 6023 animals from 752 full-sib families produced by 394 sires and 588 dams. Heritabilities estimates were 0.15 for fingerling weight, 0.21 for harvest weight and 0.32 for carcass yield. Genetic correlations were 0.77 for fingerling and harvest weight and 0.20 for carcass yield and harvest weight. Genetic trends, comparison to a randomly bred control line, and correlations between mid-parent EBVs and offspring phenotypes demonstrate positive response to selection for both traits.

Hybrid catfish, the progeny of channel catfish, Ictalurus punctatus, females × blue catfish, I. furcatus, males are in high demand by the aquaculture industry due to their superiority for pond culture. Unfortunately, fry production is a limiting factor due to lack of natural hybridization between the species and the necessity to sacrifice males for artificial fertilization. In this study, we used a quantitative genetic breeding design to assess genetic, environmental, and genotype by environment interactions to detail the genetic architecture of fitness during the “critical” early life history (ELH) stages. Males and females were crossed using a full-factorial design, creating 20 unique families. Offspring from each family were split into 2 temperature-controlled environments based on conditions that mimic early (26.6 °C) and late (32.2 °C) seasonal temperatures. Embryonic survival, hatch success, larval morphology, and deformities were quantified at hatch, mid-yolk sac transition, and swim-up stages of early development. Variation in early performance traits (calculated as variance components, VC) were partitioned to maternal/paternal effects as well as parental × environmental interactions, analyzed across and within temperatures. Embryonic survival ranged from 45 to 93% by 120°-hours post-fertilization and was not impacted by temperature. Maternal effects were responsible for large amounts of variation (VC = 51%), and paternal effects also became apparent during later stages of embryonic development but in smaller quantities (VC = ~7%). Temperature significantly impacted hatch success, in which hatch decreased at 32.2 °C (from 40% to 32%). Therefore, we conclude that temperatures at the start of the spawning season yield higher hatch success. Maternal effects were highly significant (VC = 65%), and there were also significant paternal effects (VC = 12%) with wide family variation (ranging from 14 to 71%). The deformity rate increased from 3.6% at 26.6 °C to 6.0% at 32.2 °C, but variation was driven more by maternal effects rather than temperature. For morphology, fry reared at 32.2 °C had smaller body sizes at each developmental stage. Maternal variation across morphology traits ranged widely from 9 to 80% and was highest for maternal yolk. Paternal effects/interactions ranged from to 0–29%. Genetic × environmental interactions were also observed for morphology traits since values for VCs differed within each temperature. This information showed the importance of environmental effects, parentage, and their associated interactions, which by isolating indicators of male/female quality, can be used to develop parameters for broodstock selection. Results can also be applied to improve incubation conditions for hybrid catfish during the crucial ELH stages.

Channel catfish (Ictalurus punctatus) are one of the most commercially important fish species cultured in Vietnam, and has been a major driver of Vietnam's rise to become a leading country for fisheries exports in the world. Since 2016, there have been several outbreaks of a contagious disease which in channel catfish has resulted in severe levels of economic loss. In this study, bacterial isolates from diseased fish were sampled and analyzed from 22 farms in four Northern Vietnam provinces experiencing outbreaks. Isolates were identified as Aeromonas veronii based on their bacteriological characteristics, 16S rRNA sequence analysis, and presence of Aeromonas veronii specific rpoB gene by PCR examinations. Subsequently, A. veronii isolates were tested for their virulence to fish via an experimental infection challenge, and their susceptibility to 21 antibiotics was also assessed. Results showed that A. veronii is pathogenic and has probably contributed to the mass mortality of this channel catfish species in Vietnam. Notably, A. veronii also exhibited resistance to four common antibiotics including amoxicillin, bicozamycin, lincomycin, and vancomycin. To our knowledge, this is the first report of outbreaks associated with A. veronii infection in channel catfish in a Southeast Asian country. This report could be used to alert aquaculture farmers and managers in this region to develop an appropriate biosecurity strategy for protecting catfish and other vulnerable species to A. veronii infection, and find alternative solutions to help mitigate occurences of the disease.

The Auburn University Aquaculture Genetics Program has an 80-year history with focused efforts on genetics and breeding, transgenic technology and genomics being initiated 43, 27 and 18 years ago. This resulted in the first successful selection experiments for channel catfish, Ictalurus punctatus, the basis of the monosex tilapia industry, the first production of transgenic fish in the US, major advances in catfish genomics and the first production of a xenogenic catfish. The most significant impact has been the establishment of the technology to allow a hybrid catfish industry, which produced 150 million hybrid catfish fry in 2012. Paper presented at the International Symposium on Genetics in Aquaculture XI, Auburn, AL, June 24–30, 2012.

U.S. aquaculture production of channel catfish female ( Ictalurus punctatus ) × blue catfish male ( Ictalurus furcatus ) F 1 hybrids has increased substantially due to the hybrid's improved growth, survival, carcass yield and ease of harvest compared to the more commonly farmed channel catfish. However, information on the genetic architecture underlying phenotypic variation in the hybrid which is needed to develop an efficient genetic improvement program is lacking. Progeny from two separate factorial matings between male blue catfish and female channel catfish (ten males × seven females and twelve males × five females, respectively) were grown communally in earthen ponds and measured for carcass yield and weight at approximately 520 days post-hatch. Parentage of progeny was assigned by inheritance of microsatellite genotypes. Progeny from 118 full-sib families, within 12 maternal half-sib and 22 paternal half-sib families, were measured for harvest weight ( n = 1288) and carcass yield ( n = 1101). Variance component estimates associated with dams (dam general combining ability and heritabilities based on dam half-sib families) were high, variance associated with sires (sire general combining ability and heritabilities based on sire half-sib families) were intermediate, and variance components associated with the dam × sire interactions (specific combining ability) were low for carcass yield and harvest weight. Data indicate that the genetic variance for carcass yield and harvest weight of F 1 hybrids was primarily additive. Selection for improved carcass yield and growth based on additive genetic merit of blue catfish male and channel catfish female parents should be effective for improving performance of hybrid progeny.

The objective of the this research was to determine the heritabilities and response to selection for fecundity, percent kg per kilogram body weight for channel catfish females induced to ovulate with luteinizing hormone releasing hormone analogue (LHRHa) for the production of hybrid catfish embryos. Age and/or environmental effects influences the reproductive traits measured over two spawning seasons. When the fish were three years old the relative fecundity was 10,247 and 10,127 for the select and control lines, respectively. The percent kg per kilogram female for select line was 34.7 and 3,311 and for the control was 35.5 and 3,124, respectively. Realized heritabilities were 0.10, − 0.03, and 0.06 for fecundity, percent hatch and fry per kilogram female, respectively. When the fish were four years old, the relative fecundity was 9429 and 8968 for the select and control lines, respectively. The percent hatch and fry per kilogram female for the select progeny was 9.8 and 835 and the control progeny was 13.3 and 1026, respectively. Realized heritabilities were 0.42, − 0.13, and − 0.06 for fecundity, percent hatch and fry per kilogram female, respectively. A response to selection for fecundity was observed for both years with realized heritability ranging from 0.10 to 0.42. This trait appears to have additive genetic variation and can be improved via selection. Heritabilities for percent hatch and fry/kg were near zero, and likely cannot be improved via mass selection.

Four groups of female channel catfish ( Ictalurus punctatus ) x male blue catfish ( I. furcatus ) hybrids were compared for tolerance of critically low dissolved oxygen, 0.6 ppm. Genotype–environment interactions ( P P

Four groups of female channel catfish Ictalurus punctatus × male blue catfish Ictalurus furcatus hybrids were raised communally in earthen ponds, and their body weight was evaluated at 15 and 25 months of age. When the progeny of sires and dams were pooled, hybrids produced by Rio Grande blue catfish sires exhibited faster growth, higher survival and higher production than hybrids sired by Alabama strains of blue catfish. There was a strain of dam effect at 25 months of age when the progeny from the Auburn and Marion–Kansas strains of female channel catfish had higher survival than hybrids from Auburn females alone, implying a positive effect on survival from Marion–Kansas females. Sexual dimorphism for body weight varied among genotypes. Genotype–environment (age or season) interactions occurred for several variables, demonstrating the importance of experimental design to produce research results relevant to industry. In general, strain of sire effects were more influential than strain of dam effects, which also should be considered in practical catfish genetics and breeding programs.

There is no information available whether fish naturally coinfected with Ichthyophthirius multifiliis (Ich) and Edwardsiella ictaluri can concurrently transmit both pathogens to naive fish. The objective of this study was to expose naive channel catfish ( Ictalurus punctatus ) to naturally infected fish that carried Ich and E . ictaluri to provide clinical evidence for transmission of both pathogens. Three tanks of fish were exposed to naturally coinfected fish and two tanks were utilized as mock-infected controls in each of two trials. In trial I, 34 out of 60 fish (56.7%) exposed to two infected fish per tank died at day one. All remaining fish died two days post exposure. Of the dead fish, all showed heavy Ich infection and E . ictaluri was isolated from the kidney of 60% of the dead catfish. In trial II, the cumulative mortality in fish exposed to 2 coinfected fish per tank was less than 20% during days 1–7 post exposure. Most of the fish died from 8 to 14 days post exposure to the coinfected fish. Ninety-six percent of fish were positive for both Ich and E . ictaluri in trial II. The results demonstrated that fish naturally coinfected with Ich and E . ictaluri could concomitantly transmit both pathogens to naive fish. In aquaculture management, precaution is needed to thoroughly examine fish prior to shipment or purchase to prevent the spread of aquatic animal pathogens.

Adoption of the hybrid catfish (channel catfish, Ictalurus punctatus , female × blue catfish I. furcatus , male) is increasing in the catfish industry. The most effective way to produce fry is hormone induced spawning of females coupled with hand stripping and in vitro fertilization. The success of common carp pituitary extract (CPE), luteinizing hormone releasing hormone analog (LHRHa) injections and LHRHa implants for producing hybrid catfish fry was investigated over the past 15 years. Data from 65 studies, 25, 20 and 20 for CPE, LHRHa injections, and LHRHa implants, respectively, were evaluated. Mean fry/kg female body weight (all females) produced was 948, 2483 and 2765 for CPE, LHRHa injections, and LHRHa implants, respectively. LHRHa administered as an injection or implant produced more (P

Performance traits and metabolic responses of the channel × blue hybrid catfish (Ictalurus punctatus female × I. furcatus male) in response to chronic diurnal hypoxia were evaluated in this 197-d study. Sixteen 0.1-ha earthen ponds were stocked with 15,169 hybrid catfish/ha (47 g/fish) and managed to maintain the minimum dissolved oxygen concentration greater than 12%, 24%, 36%, or 48% of saturation. Growth and yield of channel × blue hybrid catfish were significantly related to minimum nightly dissolved oxygen concentration. The cumulative effect of nocturnal dissolved oxygen concentration and the duration of exposure to hypoxia (termed dissolved oxygen-minutes) proved to be a better independent variable for regression analysis than minimum nightly dissolved oxygen concentration. Gross and net yield and mean individual weight increased curvilinearly as dissolved oxygen-minutes increased. Chronic nightly hypoxia affected daily feed consumption and channel × blue hybrid catfish in the higher dissolved oxygen treatments grew faster because they consumed a greater percentage of their body weight at each feeding. Feed consumption increased linearly in response to dissolved oxygen-minutes during the peak production period (June–August), but curvilinearly over the entire study. Body compositional indices largely were unaffected by chronic nightly hypoxia. Lipid was the primary depot affected by hypoxia and lipid indices increased with increasing dissolved oxygen concentration and with increasing total feed fed. Citrate synthase activity was 14.6% higher in the highest compared to the lowest dissolved oxygen treatment and a strong inverse relationship between citrate synthase activity and fish body mass was observed in the highest dissolved oxygen concentration treatment. Results of this study suggest that pond dissolved oxygen concentration should be maintained at 48% saturation during the peak production period (water temperatures above 25 C) and at 36% saturation during the rest of the growing season.

Mannose-binding C-type lectin (MBL) was purified by mannan-agarose affinity chromatography from blue catfish D + B ( Ictalurus furcatus ) and channel catfish NWAC 103 ( Ictalurus punctatus ) sera. The MBLs of blue catfish D + B and channel catfish NWAC 103 strains have not been purified by affinity chromatography, characterized and quantified. The affinity-purified and 2-ME reduced catfish MBLs showed one band of 66 kDa for blue catfish D + B, and one band of 63 kDa for channel catfish NWAC 103 by SDS-PAGE and Western blotting. Amino acid composition analysis (mol%) of the isolated catfish MBLs was done. The amount of methionine-S present in blue catfish D + B (0.78 mol%) was 2.2-times greater when compared with channel catfish NWAC 103 (0.35 mol%). The amount of proline present was 1.9-times greater in channel catfish NWAC 103 (8.0 mol%) when compared with blue catfish D + B (4.3 mol%). Tyrosine (2.5 mol%) was present in blue catfish D + B but not detected in channel catfish NWAC 103. N-terminal amino acid sequencing by Edman degradation for the first 10 residues gave two amino acid sequences of XRQPESFRIV and XXEDGYGKMF that were identical for both blue catfish D + B and channel catfish NWAC 103. This could represent the presence of two different isoforms of catfish MBL. Blue catfish D + B had 21.3 μg of MBL/ml of serum. Channel catfish NWAC 103 (#1 serum pool) had 15.1 μg of MBL/ml of serum (obtained in late Fall season), and channel catfish NWAC 103 (#2 serum pool) had 10.2 μg of MBL/ml of serum (obtained in Spring season). A seasonal variation in the channel catfish serum MBL was therefore seen. A standard curve for μg/ml of MBL in catfish serum was constructed with these data. The presence of MBL in blue catfish D + B and channel catfish NWAC 103 sera should be important in their innate immunity and resistance to Edwardsiella ictaluri and other microbial infections. This study describes the presence of MBL in these two Ictalurus species and evidence for a C-type lectin complement pathway of innate immunity. The channel catfish is used in aquaculture in the Southeast USA and is susceptible to bacterial infections acquired from its pond environment.

Information on the infectivity of Ichthyophthirius multifiliis (Ich), a severe fish parasite that causes high mortality, is limited for blue catfish ( Ictalurus furcatus ) and catfish hybrids (CB hybrid) resulting from female channel catfish ( Ictalurus punctatus ) × male blue catfish crosses. The objective of this study was to compare channel catfish, blue catfish and CB hybrids on the infection level and fish mortality caused by Ich using a cohabitation model. To compare the susceptibility to Ich between channel and blue catfish, fish were exposed to 5000 or 10000 theronts per fish, respectively. There were no statistical differences in the infection levels and mortalities between channel catfish and blue catfish. Channel catfish showed an infection score of 2.9 and blue catfish of 2.7 when infected by theronts at 10,000 theronts per fish. The cumulative mortalities were 86.3% and 80.6 %, respectively for channel catfish and blue catfish when exposed to theronts at 5000 theronts per fish. To compare the susceptibility to Ich between channel catfish and CB hybrid, fish were infected by cohabiting with 1 or 3 Ich-infected fish or exposure to Ich theronts at 2500–10,000 theronts per fish. Channel catfish and CB hybrid showed similar infection levels of > 150 trophonts/fish and infection duration of 7–8 days when cohabited with 1 or 3 Ich-infected fish. All channel catfish and CB hybrid exposed to theronts at the dose of 10,000 theronts/fish showed heavy infection of > 150 trophonts/fish. The cumulative mortalities were 90% and 80% for channel catfish and CB hybrid after exposure to 2500 theronts per fish. No statistical difference was found in the infection levels and mortalities using two infection methods between channel catfish and CB hybrid. Overall results indicated that CB hybrid were as susceptible to Ich as channel catfish or blue catfish.

Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen in hospitalized and debilitated hosts, especially among immunocompromised patients. Recently, S. maltophilia was isolated from channel catfish, Ictalurus punctatus , with infectious intussusception syndrome (IIS), which is the most common disease of unknown etiology of channel catfish in Sichuan Province, China. The goals of this study were to identify the bacterial strains isolated from fish with IIS collected between 2006 and 2009 in Sichuan Province, China; to evaluate the pathogenicity of the pathogen in channel catfish; and to determine the susceptibility of the pathogen strains to many currently available antimicrobial agents. All isolated strains acquired from diseased fish with IIS were identified as S. maltophilia by API 20NE identification and 16s rDNA sequencing analysis. Susceptibility of the isolates to 24 antibiotics was tested using the agar dilution method. All isolates showed a similar antibiotic susceptibility, which was characterized by resistance to all penicillins, cephalosporins, and aminoglycosides and to ambramycin, erythromycin, and rifampicin; the strains were susceptible only to some fluoroquinolones and trimethoprim + sulfamethoxazole. Virulence tests with isolated strains were conducted and pathogenicity was demonstrated: 90–100%, 65–70%, 40–50% and 0 – 5% mortalities were achieved via intraperitoneal injection of channel catfish with the different isolates at doses of 1.5 × 10 6 CFU/fish, 1.5 × 10 5 CFU/fish, 1.5 × 10 4 CFU/fish and 1.5 × 10 3 CFU/fish, respectively. This is the first report of S. maltophilia as a pathogen of channel catfish.

One of the major difficulties in selecting for superior traits for the culture of channel catfish is that most fish do not breed until they are three years old. This study was designed to decrease the time necessary to achieve puberty in channel catfish Ictalurus punctatus. Channel catfish, held under a shortened annual temperature cycle of four months of 26 C water followed by two months of 13-14 C temperature spawned at a higher rate (73%) after three temperature cycles than fish held in outdoor ponds on two normal seasonal temperature cycles (10%) or fish raised in tanks supplied with constant 26 °C water (3%). The fish were exposed to constant light in tanks until they were about 22 months old when they were stocked into outdoor spawning ponds with spawning containers. Fish held in constant warm water weighed about 1200 g and were significantly heavier than fish from the other two groups (about 600 g) when stocked into spawning ponds. Spawns from tank raised fish were significantly heavier than spawns from fish held in ponds and the shortened annual temperature cycled fish. These data suggest that the onset of the first reproductive period (puberty) is a developmental event that requires three cycles of warm and cold periods, and that weight and photoperiod have little influence on the onset of puberty.

Carvacrol and thymol are the two main active components of oregano essential oil (OEO). In this study, the effect of carvacrol and thymol was evaluated separately, in combination and in their natural composition as natural OEO. A total of five treatments, i.e., negative control group, carvacrol, thymol, a combination of carvacrol and thymol and Orego-Stim® (OS, commercial product containing natural OEO from Origanum heracleoticum L.) were added to the diets of channel catfish (Ictalurus punctatus) to investigate the effects of the respective treatments on the growth performance and antioxidant activity. After eight weeks of feeding, fishes were infected with Aeromonas hydrophila and mortality was recorded. Results of this study showed that channel catfish fed with natural OEO (OS), containing a combination of carvacrol, thymol and other minor constituents, significantly enhanced growth performance, which was the highest amongst all treatments (P

Chloramine-T (Cl-T) has been used safely and effectively to control bacterial gill disease in salmonids at a maximum exposure regimen of up to four consecutive, once-daily exposures administered for 60 min at 20 mg/L. However, data to document safe treatment concentrations of Cl-T are lacking for freshwater-reared fish other than salmonids. We report the histopathology resultant from the administration of 12 consecutive, once-daily, 180-min static immersion baths of 0, 20, 50, or 80 mg Cl-T/L to walleye (20 °C) and channel catfish (27 °C). Twelve fish of each species were euthanized immediately before the first exposure (initial controls) and then after the twelfth exposure and 7 and 14 days after the twelfth exposure. Only initial controls and fish euthanized immediately after the twelfth exposure were processed for histological review because of the general lack of exposure-related lesions in exposed fish. The only exposure-related histological changes were in the spleen where significantly greater erythrocyte swelling and necrosis was observed in channel catfish exposed at 80 mg/L relative to exposure at 0 mg/L; similar histological changes were insignificant for walleye, though there appeared to be a shift in the general category of histological change with degenerative changes (necrosis, etc.) observed following exposure at 50 or 80 mg/L compared to the inflammatory and hemodynamic changes (congestion, leukocyte infiltrate, etc.) observed in walleye exposed at 0 or 20 mg/L. The only significant change in peripheral blood cytology was that walleye fingerlings exposed at 80 mg/L had significantly fewer mature red blood cells and significantly more immature red blood cells per oil-immersion field than controls. The histopathological changes observed following exposure to Cl-T under an exaggerated exposure regimen suggest that walleye or channel catfish therapeutically exposed to Cl-T will not have treatment-related histological changes.

Whereas it is well documented that Acinetobacter baumannii is associated with human clinical infections, there are very few studies to date that report it as a pathogen for fish. In the present study, one bacterial strain was isolated from diseased channel catfish (Ictalurus punctatus) from Bingzi farm, Hefei, Anhui province, China and named as BH028, which was later identified as A. baumannii by both biochemical tests and polymerase chain reaction (PCR)-based methods and further confirmed as the causative agent by infectivity study. This is the first report on A. baumannii as a virulent pathogen for channel catfish. Exophthalmia, pale liver, and empty stomach were the main clinical signs in the affected fish. The liver might be the major target organ. The minimal inhibitory concentration (MIC) tests showed that A. baumannii was multiresistant to 10 antimicrobial agents tested.

We conducted a study to determine the effects of lipid source (poultry fat, PF or menhaden fish oil, FO) and concentration (4 or 10% lipid supplementation) in channel catfish broodstock diets on subsequent egg biochemical composition, egg production, and egg and fry quality. Three female and one male USDA-103 strain three-year-old broodfish were stocked into 16 3860-L outdoor tanks in January and randomly assigned one of the four diets (four replicates per diet). Fish were fed based on a water-temperature-dependant schedule. Spawning cans were added to tanks when water temperature reached 21 °C, and the cans were examined three times weekly for egg masses. Masses were enumerated, weighed, measured, analyzed for proximate and fatty acid composition, and incubated. Date to hatch, hatching success, fry growth and survival, and fingerling growth and survival were monitored. Supplementation of catfish broodstock diets with 10% fish oil increased spawning success, fecundity, total egg volume (matrix removed), individual egg weight, eggs·spawn− 1 (volumetric), total egg lipid concentration, hatching success, and fry survival compared to a control diet with 4% fish oil. The 10PF diet performed similarly to the 10FO diet in all measured parameters except egg fatty acid composition, although results for the 10PF diet did not always differ from those of the 4FO or 4PF diets. The 10FO diet produced significant decreases in egg saturates and MUFA, and increases in n−3 HUFAs and the ratio of n−3:n−6 fatty acids compared to all other diets. However, in fish fed the 10FO or 10PF diets the differences in egg fatty acid composition did not result in different rates of hatching success, fry survival, or fingerling production. Improved spawning performance of catfish fed 10%-lipid diets may be due partly to increased dietary energy relative to the 4%-lipid diets. Although the dietary n−3:n−6 fatty acid ratios of the 10PF (0.3) and 10FO (5.6) diets were quite different, similar concentrations of HUFAs such as DHA and AA were present in the eggs of fish fed either diet. This indicates that catfish can synthesize HUFAs from 18-carbon precursors and deposit the HUFAs in the egg, and that a variety of lipid sources may be suitable for use in catfish broodstock diets. Current methods of channel catfish egg and fry production using growout diets with 28–32% protein and 6–7% lipid are suboptimal based on the results of this study.

Streptococcus agalactiae is classified as a Lancefield's group B Streptococcus . It is one causative bacterium of streptococcosis that is responsible for severe economic losses in wild and cultured fish worldwide. S. agalactiae also causes bovine mastitis. No information is available on infectivity of cattle S. agalactiae isolates in fish. In the present study, the results showed that 10 cattle isolates from 8 different dairy farms were not infectious in Nile tilapia ( Oreochromis niloticus ) or channel catfish ( Ictalurus punctatus ) at greater than 10 8 colony forming units per fish. S. agalactiae was not re-isolated from the brain or head kidney of the fish at 24 and 48 h post-injection .

Chloramine-T is presently available in the USA to control mortalities associated with bacterial gill disease or external columnaris only through an Investigational New Animal Drug Permit authorized by the US Food and Drug Administration (FDA). Its US approval hinges on FDA's acceptance of several key data, including those describing animal safety. Chloramine-T is presently applied in US aquaculture, by permit only, once daily on consecutive or alternate days for 1 h at 10 to 20 mg/L to control mortalities associated with bacterial gill disease or external columnaris. Our objective was to determine the safety of chloramine-T bath exposures at multiples of the proposed maximum treatment concentration (i.e., 0, 20, 60, 100, and 200 mg/L) administered on four consecutive days at 20 °C to lake sturgeon Acipenser fulvescens, northern pike Esox lucius, and walleye Sander vitreum, or at 27 °C to channel catfish Ictalurus punctatus, and largemouth bass Micropterus salmoides. All fish were tested as five to eight week old fry except for walleye and channel catfish which were tested as both fry and fingerling (fingerlings were at least four weeks older than the fry tested). Walleye and channel catfish were selected to evaluate the effects of life stage (fry vs. fingerling), temperature (walleye — 15, 20, or 25 °C; channel catfish — 22, 27, or 32 °C), exposure duration (60 vs. 180 min), and water chemistry (walleye only — reconstituted soft water vs. well water). Except for channel catfish fry, survival was significantly reduced only when fish were treated at 100 or 200 mg/L. Channel catfish fry survival was significantly reduced when exposed at 60 mg/L for 180 min at 27 °C. Based on our mortality data, chloramine-T administered once daily for 60 min on four consecutive days at concentrations of up to 20 mg/L is not likely to adversely affect survival of cool or warmwater fish cultured in freshwater.

Hybrid catfish (channel catfish, Ictalurus punctatus, female × blue catfish, I. furcatus, male) can be obtained by induced spawning and artificial fertilization but with variable results. Temperature of the surrounding environment affects the rates of physiological processes in fish including time to ovulation following hormone injection and time post-ovulation when quality eggs can be obtained. Brood females were held at 24, 26, and 28 °C in 100 L aquaria and injected with LH-RHa at 20 μg/kg followed 12 h later with 100 μg/kg. Fish were monitored hourly recording the time of the first egg deposit. Some females were manually stripped soon after the first eggs were observed, and the remaining females were stripped 4–6 h after the first eggs were observed. Eggs were artificially fertilized with blue catfish sperm and incubated. The percent of females that ovulated were 52.9%, 82.4% and 95.5% at 24, 26, and 28 °C (P = 0.001) respectively. The majority of females that ovulated did so between 58 to 64 h at 24 °C, 48 to 52 h at 26 °C and 24 to 40 h at 28 °C for a degree hour response time of 1405 ± 117, 1141 ± 238 and 951 ± 261 respectively (P

Trials were conducted to determine effects of AQUI-S™ sedation during harvest (rested-harvest) on physiological responses and fillet quality of channel catfish, Ictalurus punctatus. Rested-harvest is defined as application of an anesthetic immediately before harvest to reduce fish activity associated with a normal harvest. Doses of 25–35 ppm AQUI-S™ were effective for rested-harvest of catfish (loss of equilibrium in 3 to 10 min and 100% survival following recovery). Time to loss of equilibrium and time to recovery following sedationwith35ppmAQUI-S™increasedaswatertemperature decreasedfrom30°Cto10°C.Catfish exposedto 25ppm AQUI-S™, 35 ppm AQUI-S™, 100 ppm trincaine methanesulfonate, and 8 ppm metomidate had lower blood lactate, cortisol, and glucose and higher blood pH than unsedated fish exposed to a low-water stress. Rested-harvest (RH) catfish had higher muscle and blood pH, lower blood and muscle lactate, and higher muscle ATP levels than catfish exposed to a 45 min low-water stress. Rates of muscle pH decrease, ATP decrease, and lactate increase accelerated as storage temperature decreased from 15 °C to 5 °C in RH fish acclimated to summer temperatures (33 °C), conversely these rates accelerated as storage temperature increased from 5 °C to 15 °C in RH fish acclimated to winter temperatures (7 °C). Based on physiological response (higher muscle pH, lower blood lactate, delayed time to rigor), post-sedation euthanasia by CO2 was superior to post-sedation euthanasia by AQUI-S™overdose (150 ppm), nitrogen gas, or electrical stunning. Compared to fillets from fish exposed to simulated industry transport conditions, fillets from RH/CO2 euthanised fish had higher pH 1 h post-slaughter, and less drip-loss and lower L⁎ and a⁎ color values during 7 days of iced storage. RH/CO2andcontrolfilletswerenotdifferentforshelf-lifebasedonbacterialcounts.Rested-harvestwithAQUI-S™followedbyCO2 euthanasia has potential to improve catfish fillet quality, but AQUI-S™ approval, development of rested-harvest strategies, and demonstrationofeconomicbenefitsofrested-harvestwillberequiredforadoptionofrested-harvesttocommercialcatfishproduction.

Two feeding trials were conducted to determine the effects of repetitive periods of fasting and satiation feeding on growth and production characteristics of channel catfish. In the laboratory, juvenile catfish (22 ± 2 g) were stocked into 20, 114-l tanks at a density of 25 fish per tank and fed a commercial diet in one of three feeding regimens: daily, satiation feeding for 72 days (full-fed); alternating periods of 5 days of fasting followed by 14 days of daily, satiation feeding (5-day fasted); and alternating periods of 10 days of fasting followed by 14 days of daily, satiation feeding (10-day fasted). Five-day fasted fish were fed for 57 days and fasted for 15 days (total). Ten-day fasted fish were fed for 42 days and fasted for 30 days (total). There were no differences (P > 0.05) among treatment groups in catfish weight gains (pooled mean, 24.12 ± 8.65 g), feed conversion ratios (pooled mean, 1.64 ± 0.40), or condition factors (pooled mean, 0.82 ± 0.12) when results were compared after an equal number of days (42 days) of satiation feeding. However, at termination of the feeding trial (day 72), the body weights of fish in the 5-day fasted and 10-day fasted treatments were 25% and 41% lower, respectively, than the body weight of full-fed fish. The specific growth rate (SGR) of fish in the 10-day fasted treatment (0.45 ± 0.08% day− 1) at termination of the growth trial was significantly lower than the SGR of fish in the full-fed and 5-day fasted treatments (pooled mean, 0.70 ± 0.10% day− 1), which were not significantly different. Results indicated that fish subjected to repetitive 14-day periods of satiation feeding after repeated 5-day or 10-day periods of fasting were unable to achieve the final body weight of fish fed to satiation from the beginning of the growth trial, although a compensatory growth response during each 14-day satiation feeding period usually did occur. A second experiment, conducted in 21 ponds (0.08-ha each) stocked at a density of 18,532 fish ha− 1 (mean body weight, 31 ± 1 g), evaluated the same treatments under practical production conditions. The fish were fed to satiation daily for 158 days (full-fed), 112 days (5-day fasted), or 97 days (10-day fasted) with the same diet used in the laboratory trial, and feed consumption was closely monitored to minimize waste. Fish in the 5-day fasted and 10-day fasted treatments consumed 30% and 38% less diet, respectively, than fish in the full-fed treatment during the course of the production trial. At harvest, feed conversion ratios (pooled mean, 2.17 ± 0.35) and protein efficiency ratios (pooled mean, 1.43 ± 0.26) did not differ (P > 0.05) among treatments. Mean body weights of fish in the 5-day fasted and 10-day fasted treatments were 24% and 29% lower (P ≤ 0.05), respectively, than the mean body weight of full-fed fish; however, the yield (kg ha− 1) of pond-run fish (all sizes) in the 5-day fasted treatment did not differ significantly from the yield of pond-run fish in the full-fed treatment. The SGR of fish in the full-fed treatment (1.75 ± 0.25% day− 1) was significantly higher than the SGR of fish in the 5-day fasted and 10-day fasted treatments (pooled mean, 1.42 ± 0.11% day− 1), which were not significantly different. The yield of marketable (≥ 0.46 kg) fish in the full-fed and 5-day fasted treatments (pooled mean, 3441 ± 936 kg ha− 1) did not differ significantly, but the mean body weight of marketable fish in the 5-day fasted treatment (470 ± 30 g) was lower (P ≤ 0.05) than that of marketable fish in the full-fed treatment (570 ± 30 g). Under the conditions of this study, the diet-related cost of producing 1 kg of pond-run fish (US$0.57–0.68 kg− 1) did not differ significantly among treatments. The diet cost of producing marketable fish in the 5-day fasted treatment was lower (P ≤ 0.05) than the diet cost of producing marketable fish in the 10-day fasted treatment, but not different (P > 0.05) from the diet cost of producing marketable fish in the full-fed treatment. Results indicated that feeding practices which incorporate repetitive periods of fasting and satiation feeding could provide economic benefits through reduced feed and labor costs.