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The hybrid between the female channel catfish (Ictalurus punctatus) and the male blue catfish (I. furcatus) is the best genetic type currently available for commercial catfish farming due to their superior traits. However, further genetic improvements can be achieved by selecting parents with increased combining abilities. Twenty female channel catfish and twelve male blue catfish were crossed in a partial factorial mating design, resulting in forty hybrid families. These families were evaluated for early growth in three different rearing systems, including ponds and aquaria. The early growth performance of hybrid catfish was significantly (p < 0.05) affected by the additive gene action of the female parent and the male parent. There were genotype–environment or genotype–age interactions affecting the combining abilities, both the amount and the type of genetic variation. Dam GCA was significant in all environments/ages; however, sire GCA was variable, and SCA was not significant. These findings suggest that reciprocal recurrent selection for growth could potentially improve the performance of F1 hybrid catfish. [ABSTRACT FROM AUTHOR]

The melanocortin-4 receptor (MC4R) plays a critical role in homeostasis and the regulation of body weight. Polymorphisms in the mc4r gene have been discovered and linked to growth, carcass composition, and meat quality traits. Therefore, we used the CRISPR-Cas9 system to target the mc4r gene in the most important freshwater aquaculture species in the USA, channel catfish, Ictalurus punctatus. Guide RNAs were designed to direct the Cas9 to the coding sequence of the channel catfish mc4r gene. gRNA(s)-Cas9 mixtures were delivered into one-cell embryos using electroporation and microinjection. For each treatment, the nature and rate of mutations were analyzed. Hatching and survival rates were calculated. The overall mutation rates were 30.6% and 66.7–90.6% for electroporation and microinjection, respectively. Mutated fish generated via electroporation or microinjection exhibited 38% and 20% improvement in body weight, respectively, when compared with the full-sib control. The mean feed conversion ratio of the mutants was 1.18 compared with 1.57 in the control fish. The improved growth and feed conversion indicate that the generation of mc4r-edited fish could economically benefit aquaculture production. [ABSTRACT FROM AUTHOR]

Simple Summary: Gonadotropin-releasing hormone (GnRH) plays a pivotal role in fish reproduction. In the present study, transcription activator-like effector nuclease (TALEN) plasmids targeting the catfish gonadotropin-releasing hormone (cfGnRH) gene were delivered into fertilized eggs with double electroporation to sterilize channel catfish (Ictalurus punctatus). After low fertility was observed, application of luteinizing hormone-releasing hormone analog (LHRHa) hormone therapy resulted in good spawning and hatch rates for mutants (individuals with human-induced sequence changes at the cfGnRH locus). Gene editing of channel catfish for the reproductive confinement of gene-engineered, domestic, and invasive fish to prevent gene flow into the natural environment appears promising. Transcription activator-like effector nuclease (TALEN) plasmids targeting the channel catfish gonadotropin-releasing hormone (cfGnRH) gene were delivered into fertilized eggs with double electroporation to sterilize channel catfish (Ictalurus punctatus). Targeted cfGnRH fish were sequenced and base deletion, substitution, and insertion were detected. The gene mutagenesis was achieved in 52.9% of P1 fish. P1 mutants (individuals with human-induced sequence changes at the cfGnRH locus) had lower spawning rates (20.0–50.0%) when there was no hormone therapy compared to the control pairs (66.7%) as well as having lower average egg hatch rates (2.0% versus 32.3–74.3%) except for one cfGnRH mutated female that had a 66.0% hatch rate. After low fertility was observed in 2016, application of luteinizing hormone-releasing hormone analog (LHRHa) hormone therapy resulted in good spawning and hatch rates for mutants in 2017, which were not significantly different from the controls (p > 0.05). No exogenous DNA fragments were detected in the genome of mutant P1 fish, indicating no integration of the plasmids. No obvious effects on other economically important traits were observed after the knockout of the reproductive gene in the P1 fish. Growth rates, survival, and appearance between mutant and control individuals were not different. While complete knock-out of reproductive output was not achieved, as these were mosaic P1 brood stock, gene editing of channel catfish for the reproductive confinement of gene-engineered, domestic, and invasive fish to prevent gene flow into the natural environment appears promising. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 <.0001) for final body weights among genetic groups. Condition factor, growth and survival were not perfectly correlated, and genotype-environment interactions occurred for the overall phenotype. Apparently, GH can play a critical positive role for channel catfish under osmotic stress, which has relevance for aquaculture management under future global climate change. Optimum performance for all genotypes was observed with slightly elevated, 2.5 ppt. Although, GH transgenic catfish were less affected than non-transgenic channel catfish at 5–7.5 ppt, their performance was sub-optimal. GH transgenic fish are beneficial for use in culture environments that have slight shifts in salinity in the future, but they are only a partial solution for future environments at 5 ppt and higher. • GH transgenic channel catfish had higher survival rate than their non-transgenic siblings at 7.5 ppt. • Massive mortality occurred for different genetic groups during the second week at 7.5 ppt except for GH transgenic fry. • Swim-up fry of different genetic groups had better growth in 2.5 ppt than 0 ppt. • Genotype-environment interactions occurred for the overall phenotype. [ABSTRACT FROM AUTHOR]