UTILIZATION OF DIFFERENT DIET FORMULATIONS IN MARINE SPECIES, EFFECT OF SALINITY ON GROWTH AND SERUM OSMOLALITY OF YELLOWTAIL SNAPPER, Ocyurus chrysurus, AND DETERMINATION OF METHIONINE REQUIREMENT IN PACIFIC WHITE SHRIMP, Litopenaeus vannamei

Abstract

Marine fish and invertebrate aquaculture is a substantial source of animal protein and one of the fastest growing food sectors in the world. The current need in developing high quality and nutritionally-complete feed in promoting optimal animal growth has been the constant challenge in the aquaculture industry. Three main diets were made to determine the methionine requirement in practical diets for Litopenaeus vannamei – a deficient basal diet, a replete diet with DL-Met and Met-Met-supplemented diet, and a replete diet with corn protein concentrate. Ten experimental diets were produced by blending the main diets, with graded methionine levels. Significant differences were observed in weight gain and shrimp whole body amino acids. Results confirmed that in the presence of replete cystine, a conservative methionine requirement was estimated by a one-slope broken-line regression analysis model at 0.61% diet (1.68% protein) is recommended. The present work evaluated protein sources fishmeal, poultry meal, and solvent-extracted soybean meal and determine SBM-induced enteritis in yellowtail snapper, Ocyurus chrysurus. Growth performance, histological measurements, and scoring of the distal intestine showed no significant differences in yellowtail snapper when fed diets containing reduced levels of fishmeal and 40% SBM. Dietary protein and lipid levels were evaluated by conducting a 14-week trial using diets with varying protein (36%, 40%, and 44%) and lipid levels (6%, 10%, and 14%), and a 10-week trial with diets having 36% protein and incremental lipid levels (7%, 10%, 13%, and 16%). We recommend 36% protein and dietary lipid levels of 7%-13%, which are lower than currently used commercial diets for marine finfish. Knowledge from the current study is helpful in formulating cost-effective feed and promote sustainable yellowtail snapper aquaculture. Salinity tolerance in salinity conditions of 3 to 32 g/L was evaluated, followed by a six-week growth trial with salinities of 6 to 32 g/L. Significant differences were observed for survival in fish reared in 6 g/L, and for biomass, with highest weights in 12 to 16 g/L. Such findings serve as initial data in the possible potential of yellowtail snapper culture in lower salinity conditions to promote its cultivation, and open sustainable and economic mariculture approaches.