The overall baseline (as received) moisture, protein and fat content of hybrid catfish (Ictalurus furcatus x Ictalurus punctatus) fillets were 77.8 +/- 1.38%, 16.7 +/- 0.50% and, 5.7 +/- 1.6%, respectively. Small fillets (111 +/- 19 g) had higher (P≤0.05) baseline moisture (78.6 +/- 0.87% vs 76.8 +/- 1.15%) and lower (P≤0.05) fat content (4.7 +/- 0.64% vs 6.8 +/- 1.72%) than large fillets (247 +/- 62 g), whereas protein content was similar (P>0.05) for both sizes. Retained water of the final fresh and frozen fillets was 1.2 +/- 2.03% and 3.1 +/- 1.02%, respectively, irrespective of fillet size. Psychrotrophic (PPC) and total coliform plate counts (TCC) of the baseline fillets were 4 log CFU/g and 1.6 log CFU/g, respectively and were not different between the process steps, except after injection which was higher (P>0.05) than baseline. Moisture-protein ratio and fat content were good (P≤0.05) predictors for retained water in catfish fillets during processing.

Incidence and prevalence of Edwardsiella piscicida has increased in Mississippi farm-raised catfish in recent years. Edwardsiella piscicida affects mostly market-sized catfish during the final stages of the production cycle resulting in significant economic losses. The objectives of this study were to determine the genetic variability of E. piscicida, assess virulence in channel and hybrid catfish, and evaluate the capacity of a live-attenuated E. ictaluri vaccine to protect channel and hybrid catfish against heterologous E. piscicida isolates. This work identified five discrete E. piscicida lineages, along with group specific associations of several virulence related genes. In general, E. piscicida was shown more virulent in hybrids than channel catfish, in line with previous work. Further, a live-attenuated E. ictaluri vaccine was shown to confer cross-protective immunity in channel and hybrid catfish against E. piscicida.

Channel catfish (Ictalurus punctatus) have a broad distribution from Canada to Mexico, suggesting that different strains may have different thermal tolerances. In aquaculture, daily temperature maximums up to 36-40°C and fluctuations of 3-6°C occur, and may be exacerbated by future climate change. To quantify differences in thermal tolerance amongst geographically-distinct channel catfish strains and corresponding hybrid catfish (I. punctatus x [blue catfish] I. furcatus): acute critical thermal maximum (CTmax), and the effects of chronic thermal regimes on growth, survival and differential gene expression were examined. Southern channel catfish had higher CTmax than northern, and channel catfish had higher CTmax than hybrid catfish. Under chronic thermal stress, hybrid catfish had the greatest survival and most consistent growth. Further, northern channel catfish had the greatest magnitude and largest amount of upregulated gene transcripts in response to high temperatures, indicating greater thermal stress. Therefore, catfish thermal tolerance varies by geographic region and species.

Commercial production of catfish is the leading aquaculture industry in the United States. Production in Mississippi, Louisiana, Alabama, and Arkansas representing 96% of the total catfish sales in the USA. In 2017, the USDA-FSIS added testing of generic Escherichia coli and Enterococcus to the sampling of Siluriformes. The incidence of Escherichia coli in fish and seafood has been associated with possible fecal matter contamination. However, this indicator bacteria could also be a part of the natural microflora of catfish ponds where processing plants collect hybrid catfish. Aerobes, Psychrotrophs, Coliforms, Escherichia coli, and Enterobacteriaceae counts among environmental, liquid and fish samples were tested every season and periodically during one day of operation. Generic Escherichia coli counts were greater in late Summer (P ≤ 0.05) for liquid samples (1 log CFU/g) . During the day, Escherichia coli appeared to be more recurrent in the afternoon at the skinning step (P ≤ 0.05).