The effect of high water temperatures on the allometric scaling effects of energy and protein starvation losses in juvenile barramundi, Lates calcarifer

Abstract

This study was undertaken to examine the effects of high water temperatures on the allometric scaling effects of energy and protein starvation losses by juvenile barramundi, Lates calcarifer. The somatic energy and protein loss was examined in fish of varying sizes when starved for 24 or 25 days at temperatures ranging from 23 °C to 38 °C. The amount of energy and protein lost varied according to both size and temperature and was consistent with the function of a*W(b), where a is a temperature dependent coefficient, W the animal's weight and b an exponent relating energy loss to live-weight. The coefficient for energy or protein loss varied and was described by a polynomial function, with a general increase from 23 °C to 32 °C, before a dramatic decline after 35°C. In contrast, the exponent for energy loss was relatively constant between 23 °C and 35 °C, but showed a rapid increase at 38 °C. Both the coefficients and exponents of protein loss mirrored that of energy loss. Analysis of the protein and lipid contributions to energy loss shows that typically lipid loss accounts for the greater part of energy loss (~67%), but also shows that above 35 °C protein energy loss increases (from ~33% to ~39%) while the losses seen from lipid catabolism remain the same. These results show that one of the main nutritional issues associated with heat stress in fish is a dramatic increase in endogenous loss of protein.