EFFECT OF RATION AND BODY-SIZE ON THE ENERGY BUDGET OF JUVENILE WHITESTURGEON

Growth and energy budget were measured for three sizes(2.4, 11.1 and 2 2.5 g) of juvenile white sturgeon Acipenser transmontanus held at 18.5 degrees C and fed tubificid worms at different levels ranging from st arvation to ad libitum. For each size-class, specific growth rate incr eased linearly with increasing ration, and conversion efficiency was h ighest at the maximum ration. Growth rate decreased with increasing fi sh size at the maximum ration, but increased with size al each restric ted ration. Conversion efficiency increased with increasing ration for each size-class and was usually highest at the maximum ration. Faecal production accounted for 3.2-5.2% of food energy. The proportion of f ood energy lost in nitrogenous excretion decreased with increasing rat ion. With increases in ration, the allocation of metabolizable energy to metabolism decreased, while that to growth increased. Fish size had no significant effect on the allocation of metabolizable energy to me tabolism or growth. Al the maximum ration, on average 64.9% of metabol izable energy was spent on metabolism, and 35.1% on growth. (C) 1996 T he Fisheries Society of the British Isles