INFLUENCE OF STARVATION AT LOW-TEMPERATURES ON UTILIZATION OF ENERGY RESERVES, APPETITE RECOVERY AND GROWTH CHARACTER IN SEA BASS, DICENTRARCHUS-LABRAX

The effect of starvation at selected low temperatures was studied in sea bass, Dicentrarchus labrax. The work focused on proximate chemical constituents and blood glucose. Appetite and growth of starved, refed specimens were also examined. Two experimental sets were designed. In one set the fish were exposed to 3-degrees-C, 7-degrees-C and 11-degrees-C and in the other to 3-degrees-C, 8-degrees-C and 13-degrees-C. Survival of the fish in the experimental conditions was 99.7%. Appreciable loss in body weight occurred. The reduction wss more marked in the first week. No significant difference in chemical composition occurred in the first two weeks of starvation. Prolongation of food deprivation resulted in decline of lipid content with a corresponding increase in water content. This trend was the more marked at high temperature. Liver glycogen was the most readily utilizable source of energy. Lipid yielded energy after which proteins were mobilized to save further loss of lipid. Lipid exerted a sparing role for glycogen. The preference for different energy sources depended on exposure temperature and duration of starvation. Lipid chiefly supplied the energy needs of the 3-degrees-C test groups, whereas liver glycogen provided the calorific requirements of fish at 7-degrees-C, 8-degrees-C, 11-degrees-C and 13-degrees-C. In the 3-degrees-C test groups gluconeogenesis occurred after 2 weeks. The products of lipid breakdown may have served as substrates for glycogen biosynthesis. High tolerance of sea bass to low temperature was attributed to high fat content and hyperglycemia. The study also pointed to the involvement of some organs other than liver in generating glucose from their glycogen stores following exhaustion of hepatic glycogen. Starvation stress at the lowest temperatures adversely affected the return of the fish's appetite and growth characters. Compensatory growth occurred in sea bass refed after starvation. The findings have implications for aquaculture management procedures.