Submitted to: Journal of Fish Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/18/2003
Publication Date: 1/1/2004
Citation: Small, B.C. 2004. Effect of dietary cortisol administration on growth, physiological conditions, and reproductive success of channel catfish. Journal of Fish Biology 64:589-596. Interpretive Summary: Spawning success on a commercial catfish farm may average less than 50% in a given year. Several studies have examined the effects of various hormone treatments on improving spawning success. One such hormone, cortisol, appears to have both positive and negative effects on fish reproduction depending on the species being studied. In the present study, the effect on reproductive performance on feeding cortisol to channel catfish during the spawning season was examined. Channel catfish fed dietary cortisol had an average of 41.9% more spawns than those fed a cortisol-free diet, suggesting cortisol plays a positive role in channel catfish reproduction. With this information, new cortisol-based treatments can be developed to improve channel catfish spawning success for the United States catfish industry.
Technical Abstract: The effect of cortisol administration on reproductive performance was investigated in channel catfish Ictalurus punctatus broodfish. Cortisol was added to a commercial catfish feed by dissolving in ethanol and spraying the feed to yield a dietary concentration of 150 mg/kg feed. The cortisol diet and the control (no cortisol) diet were offered at a rate of 1% of biomass to three replicate ponds, respectively, three times per week for 11 weeks. Spawning began 10 d after the start of the experiment, and continued for 10 weeks. In fish fed cortisol, body weight and hepato-somatic index were reduced (P </= 0.02) and concentrations of plasma cortisol and glucose were significantly higher (P </= 0.0003) compared to controls. The relative frequency of spawning was similar between the two treatments; however, cortisol-fed catfish had an average of 41.9% more spawns than the control-fed fish. On average, cortisol-fed broodfish spawned 25.5 times compared to 12.3 spawns for those fish in control ponds (P = 0.10). No effect was observed on egg production, with individual egg weight, fecundity, and hatching success being similar (P >/= 0.27) for both treatments. Despite the observed negative effects of cortisol on somatic and hepatic growth, the increased reproductive output coupled with no observable effects on the eggs or hatching success demonstrates that cortisol does not suppress catfish reproduction, but may have a positive physiological role, similar to that reported for other species.