Seasonal Trends in Intestinal Bacterial Flora of Farm-Raised Channel Catfish

Abstract

The bacterial floras in the alimentary tracts of farm-raised channel catfish Ictalurus punctatus were qualitatively examined. Fish were raised in six different earthen ponds in Mississippi stocked at three different densities. Fish stocking density had no detectable effect on the composition of the microflora. In total, 26 different species of bacteria from 20 different genera were isolated. Jaccard similarity indices were highest (>0.5) for the groups July-September, October-December, and February-March, implying seasonality of the bacterial flora complex in the middle intestine. The predominant microflora consisted of gram-negative rods, with Aeromonas sobria and A. hydrophila being the most prevalent. Clostridium spp. were also consistently isolated throughout the sampling period. Bacteria present seasonally were Escherichia coli, Klebsiella pneumoniae, Plesiomonas shigelloides, Streptococci (group D) not enterococcus, Moraxells spp., and Citrobacter spp. Ambient seasonal temperature variation could account for some of the bacterial population variation. Presence of fecal coliform bacteria in the intestines of farm-raised catfish suggests that care should be exercised during processing to prevent contamination of edible meat.