FACTORS AFFECTING THE PROXIMATE COMPOSITION OF CULTURED FISHES WITH EMPHASIS ON SALMONIDS

The endogenous and exogenous factors reported to affect the proximate composition of cultured fishes, with emphasis on salmonids, are examined. Methods of reporting and comparing proximate composition are discussed. Examination of measurements presented in a number of published papers, using allometric analysis, indicates that comparison of proximate compositions on a dry weight basis and failure to include fish size as a covariate have, in many cases, led to erroneous conclusions concerning the effects of environmental and dietary factors on the proximate composition of cultured fishes. Available evidence indicates that the protein content of growing salmonids is determined solely by fish size (is endogenously controlled), that lipid level is effected by both endogenous and exogenous factors, that ash content is homeostatically controlled, and that whole body moisture is inversely related to body lipid. The implications of the present findings to nutrition studies and the potential for modification of carcass composition in cultured fish are discussed.