EFFECT OF TEMPORARY REDUCTIONS IN FEEDING ON PROTEIN-SYNTHESIS AND ENERGY-STORAGE OF JUVENILE ATLANTIC SALMON

Biochemical and tissue-composition indices were used to determine the impacts of temporary feeding reductions on juvenile Atlantic salmon (4 .2 g initial weight). Three levels of food reduction (fasting, 20% of control, 50% of control) lasting for 2, 4 or 8 days were compared to a control group (constant feeding at 2.75% of body weight day(-1)). Orn ithine decarboxylase (ODC) activity and RNA concentrations were used t o measure changes in protein synthesis; condition factor (K), liver-so matic index (LSI), visceral-somatic index (VSI), and gut index (GI) we re used to provide information on stored energy levels. Results showed that physiological adjustments to decreases or increases in feeding o ccur very quickly. The most rapid responses were changes in ODC activi ty (within 2 days) and LSI (2-4 days). Charges in RNA concentrations a nd K required 4-8 days. There was no apparent effect of tie treatments on VSI or GI. Temporary reductions of feeding lasting 2 days or less would not be detected by any index except ODC activity. Changes in the indices are discussed with respect to short-term changes in rates of protein synthesis and energy storage. (C) 1996 The Fisheries Society o f the British Isles