REPLACEMENT OF FISH MEAL BY ALTERNATIVE PROTEIN SOURCES IN DIETS FOR JUVENILE BLACK SEA BASS

Fish meal is the protein source traditionally used in aquaculture diets, yet it is a limited resource and is expensive. Alternative protein sources can lower the cost of aquaculture diets, reduce the amount of wild fish used as protein, and potentially reduce the nutrient levels in effluent waste. Soybean meal, poultry-by-product meal, and meat-and-bone meal have high protein contents and amino acid profiles similar to that of fish meal. They are readily available and less expensive than fish meal. In a previous study, black sea bass fed diets with up to 60% of the fish meal replaced by soybean meal showed no significant differences in growth rates compared to those fed a control FM diet (Alam et al., unpublished data). Based on these results, five diets were formulated that replaced fish meal protein by soybean meal at 0, 60, 70, 80, 90 and 100%. In addition, a diet with 60% of the fish meal replaced by poultry by-product meal and a diet with 30% of the fishmeal replaced by meat-and-bone meal was formulated. These substitution levels were decided based upon published information for other marine finfish. All diets were formulated to have the same protein level (44% crude protein) and lipid level (10%). All diets contained the same amount of attractants (alanine, glycine, betaine, and taurine), vitamin and mineral premix, and wheat gluten as a binder. All diets contained 5% krill meal and 7.5% squid meal to enhance the palatability. Menhaden fish oil and soybean lecithin were used as lipid sources and cellulose was used as a filler. The diets were prepared at the UNCW. Triplicate groups of 15 juvenile black sea bass (average initial weight = 10 g) were fed to apparent satiation twice daily for 10 weeks. Fish were held in 75 liter rectangular tanks supported by a recirculating seawater system. At the end of the experiment, survival was greater than 86% for all dietary treatments with no significant differences. No significant differences (P<0.05) in growth, liver tissue proximate composition, muscle tissue moisture, protein and ash, and whole boy moisture and protein were observed between fish fed the diets replacing 60% or 70% of the fish meal protein with soybean meal compared to fish fed the fish meal diet. No significant (P< 0.05) differences in growth, whole body proximate composition, digestive organ proximate composition, liver tissue proximate composition, and muscle tissue moisture, protein or ash were observed between fish fed the diet with 30% of the fish meal protein replaced by PBM compared to fish fed the fish meal diet. No significant P<0.05 differences in muscle tissue proximate composition, liver tissue proximate composition, digestive organ proximate composition and whole body moisture, lipid or ash were observed between fish fed the diet with 30% of the fish meal protein replaced by MBM compared to fish fed the fish meal diet. Results indicated that fish meal protein maybe replaced by soybean meal (without amino acid supplementation) at levels up to 70% in the diets of juvenile black sea bass with, no dimution of fish performance. Fish meal replacement by meat-and-bone meal and poultry by-product meal at levels of at least 30% and 60%, respectively, were also successful, with higher substitution levels possible.