High stocking density alters growth performance, blood biochemistry, intestinal histology, and muscle quality of channel catfish Ictalurus punctatus

Stocking density is one of the major factors affecting production and welfare of fish in aquaculture. This study investigated the effect of different stocking densities on growth, feed efficiency, blood biochemistry, histometric response, muscular composition, and flesh quality of channel catfish Ictalurus punctatus. Fish were cultured at low, medium, and high stocking density of 50, 150, and 300 fish m(-3), respectively, for 60 days in the re-circulating aquaculture system. Fish growth and feed efficiency significantly decreased with increasing stocking density. Serum concentrations of glucose, triglyceride, and total cholesterol, as well as the activities of both aspartate aminotransferase and alanine aminotransferase, significantly elevated as stocking density increased. High stocking density led to the decline in serum levels of thyroid hormones. The villi length and its number, as well as the size of goblet cells in the intestine, were negatively affected by high stocking density. There was a significant density-dependent decrease in muscular fat content, diameter of dorsal muscle fiber, intensity of muscular bundles, and percentage of muscular bundles area in dorsal muscle. However, the percentage of the intramuscular connective tissue showed a significant increase in fish reared at high stocking density. Fish stocked in high density exhibited the decrease in muscle pH, drip loss, and frozen leakage rate. Overall, the increased stocking density could cause the unfavorable impacts on growth, feed efficiency, histological change, and flesh quality of I. punctatus.