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.

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.

Follicle-stimulating hormone (fsh) plays an important role in sexual maturation in catfish. Knocking out the fsh gene in the fish zygote should suppress the reproduction of channel catfish (Ictalurus punctatus). In this study, transcription activator-like effector nuclease (TALEN) plasmids targeting the fsh gene were electroporated into fertilized eggs with the standard double electroporation technique. Targeted fsh cleavage efficiency was 63.2% in P₁fsh-knockout catfish. Ten of fifteen (66.7%) control pairs spawned, and their eggs had 32.3–74.3% average hatch rates in 2016 and 2017. Without hormone therapy, the spawning rates of P₁ mutants ranged from 33.3 to 40.0%, with an average egg hatching rate of 0.75%. After confirmation of the low fertility of P₁ mutants in 2016, human chorionic gonadotropin (HCG) hormone therapy improved the spawning rates by 80% for female mutants and 88.9% for male mutants, and the mean hatch rate was 35.0% for F₁ embryos, similar to that of the controls (p > 0.05). Polymerase chain reaction (PCR) identification showed no potential TALEN plasmid integration into the P₁ channel catfish genome. Neither the P₁ nor the F₁ mutant fish showed any noticeable changes in in body weight, survival rate, and hatching rate when the reproductive gene was knocked out. F₁ families had a mean inheritance rate of 50.3%. The results brought us one step closer to allowing implementation of certain genetic techniques to aquaculture and fisheries management, while essentially eliminating the potential environment risk posed by transgenic, hybrid, and exotic fish as well as domestic fish.

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.

The confinement of transgenic fish is essential to prevent their escape and reproduction in natural ecosystems. Reversible transgenic sterilization is a promising approach to control the reproduction of transgenic fish. Therefore, the present study was conducted to develop a reversibly sterile channel catfish (Ictalurus punctatus) via the transgenic overexpression of the goldfish (Carassius auratus) glutamic acid decarboxylase (GAD) gene driven by the common carp (Cyprinus carpio) β-actin promoter to disrupt normal gamma-aminobutyric acid (GABA) regulation. Three generations of GAD-transgenic fish were produced. All studied generations showed repressed reproductive performance; however, this was not always statistically significant. In F₁, 5.4% of the transgenic fish showed a sexual maturity score ≥ 4 (maximum = 5) at five years of age, which was lower (p = 0.07) than that of the control group (16.8%). In the spawning experiments conducted on F₁ transgenic fish at six and nine years of age, 45.5% and 20.0% of fish spawned naturally, representing lower values (p = 0.09 and 0.12, respectively) than the percentages in the sibling control fish of the same age (83.3% and 66.7%, respectively). Four of six pairs of the putative infertile six-year-old fish spawned successfully after luteinizing hormone-releasing hormone analog (LHRHa) therapy. Similar outcomes were noted in the three-year-old F₂ fish, with a lower spawning percentage in transgenic fish (20.0%) than in the control (66.7%). In one-year-old F₂-generation transgenic fish, the observed mean serum gonadotropin-releasing hormone (GnRH) levels were 9.23 ± 2.49 and 8.14 ± 2.21 ng/mL for the females and males, respectively. In the control fish, the mean levels of GnRH were 11.04 ± 4.06 and 9.03 ± 2.36 ng/mL for the females and males, respectively, which did not differ significantly from the control (p = 0.15 and 0.27 for females and males, respectively). There was no significant difference in the estradiol levels of the female transgenic and non-transgenic fish in the one- and four-year-old F₂-generation fish. The four-year-old F₂-generation male transgenic fish exhibited significantly (p < 0.05) lower levels of GnRH and testosterone than the control fish. In conclusion, while overexpressing GAD repressed the reproductive abilities of channel catfish, it did not completely sterilize transgenic fish. The sterilization rate might be improved through selection in future generations.