Changes in Fatty Acid Composition Associated with Body Silvering in Biwa Salmon Oncorhynchus rhodurus and Amago Salmon O. rhodurus

Abstract

Changes in lipid content, lipid class composition, and fatty acid composition in wild and cultur-ed biwa and amago salmon underyearlings were examined during the period of body silvering. Cultured biwa salmon showed slight changes in these components of the muscle during body sil-vering. Although cultured amago salmon parr showed seasonal fluctuations in the components, the smolts did not show definite difference as compared with the parr in early smolting season. On the other hand, wild biwa salmon displayed a marked difference in the lipid class composition and fatty acid composition between the parr in the river and the silvery fish in the lake. In silvering biwa salmon, depletion of 16:1, 18:2n6, 18:3n3 and increase in 22:6n3 of nonpolar lipids were observed, the pattern being similar to the marine fish lipid. Since no change was seen in cultured biwa salmon, differences in the lipid class and fatty acid compositions between the parr in the river and the silvery fish in the lake in wild biwa salmon seem to be related to differences in their feeding habit and/or in swimming activity.