Dietary manipulation of lipid deposition and cold tolerance in juvenile red drum, Sciaenops ocellatus

Two concerns of aquaculturists who produce red drum, Sciaenops ocellatus, are excessive lipid deposition and the susceptibility of this species to cold kill in outdoor ponds during severe winters. Alteration of lipid deposition and cold tolerance in cultured red drum was investigated in eight feeding trials utilizing various kinds of dietary lipids and compounds known to affect lipid metabolism. Baseline proximate composition of wild red drum was established from fish taken over a 1-year period from canals at the Dow Chemical Plant in Freeport, Texas. The liver was determined to be a major depot for lipid and protein, with these two components having an inverse relationship. Wild red drum stored high levels of lipid in their liver without any apparent detrimental effects. Cultured juvenile red drum had composition of muscle and liver lipid similar to that of wild red drum, although the cultured juveniles had slightly higher liver lipid when compared to the wild fish during summer months. Relative to wild fish, cultured fish had elevated intraperitoneal fat when they were fed certain experimental diets.;Experiments involving several dietary lipids suggested that appropriate manipulation of diet composition can minimize undesirable lipid deposition. Fish fed menhaden oil or saturated lipids such as coconut oil or beef tallow had adequate growth, but only coconut oil produced minimal lipid deposition in the muscle and peritoneal cavity. Juvenile red drum were not able to efficiently utilize medium-chain triglycerides (tricaprylin) at any inclusion level. Dietary lecithin consistently increased weight gain and feed efficiency of juvenile red drum. Lecithin increased liver lipid and had no effect on muscle lipid, while supplemental choline shifted lipid deposition from the liver and towards the muscle.;Cold tolerance of juvenile red drum was increased by feeding diets rich in (n-3) highly unsaturated fatty acids. Median lower lethal temperatures were significantly reduced in fish fed diets containing menhaden oil during chronic cold tolerance assays. Salinity (5 and 32...