Development of improved catfish germplasm at the warmwater aquaculture research unit, DSDA - ARS

Farm-raised catfish is the largest aquaculture enterprise in the U.S. in terms of both production volume and value. The USDA-ARS Warmwater Aquaculture Research Unit (WARU) mission includes development and release to farmers of catfish germplasm improved for economically important traits. Historically, the channel catfish (Ictalurus punctatus) comprised nearly all U.S. farm-raised catfish production, but in the last 10 years, production of the F1 hybrid between the channel catfish and blue catfish (Ictalurus furcatus) has increased to about 50% of total production. Therefore, the WARU breeding program is focused on genetic improvement of purebred channel catfish and F1 hybrid catfish performance. The channel catfish improvement program has used selection on BLUP breeding value estimates to improve growth rate and carcass yield. We started with a diverse population of channel catfish derived from 10 commercial farms in 2006 and have evaluated over 21,000 animals from 750 full-sib families produced by 408 sires and 624 dams between 2008 and 2015. Heritabilities for harvest weight and residual carcass weight are 0.29 and 0.36, respectively, and fish are selected based on an index that puts equal weight on individual breeding values for growth and family average breeding values for residual carcass weight. Improvements in growth have been 8 - 10% per generation and are in agreement with expected improvements. Increases in residual carcass weight have been less substantial (-2 g per generation) than those for harvest weight due, at least in part, to the necessity for selection on less accurate family average breeding values for carcass weight. The hybrid catfish improvement program has focused on evaluation, identification and selection of blue catfish sires that produce superior performing hybrid progeny. We initiated a program to collect several blue catfish populations and evaluate performance of their purebred and hybrid progeny. Initial evaluations suggest the majority of genetic variance for growth in hybrid progeny is additive in nature, and populations and individual sires that produce purebred blue catfish progeny with faster growth also produce hybrid progeny with faster growth. We have ongoing experiments to estimate heritabilities and genetic correlations in the purebred blue and hybrid catfish, which will give us direction in selecting purebred blue catfish for improved hybrid catfish performance. We use DNA markers to identify parentage and establish pedigrees in our populations and are developing a SNP chip to be used for genomic selection to improve our breeding value accuracy and rate of improvement, particularly for carcass yield. We are evaluating other traits for inclusion in our selection index, and are collecting and cryopreserving sperm from superior channel and blue catfish sires for future use. This combination of traditional animal breeding, genomic selection and cryopreservation will result in improved catfish germplasm, improved production efficiency and greater profitability for catfish farmers.