Content of lipid components in juveniles of Salmo trutta L. from the Orzega river (Onega lake basin) I. Dynamics of fatty acids during the process of growth and development in juveniles of brown trout (at the age of 1+, 2+, 3+)

The fatty acid status in juveniles of brown trout (at the age of 1+, 2+, 3+) from the Orzega river (Onega Lake Basin) collected in summer was studied. It was shown that the level of essential 18:2n-6 and 18:3n-3 fatty acids in the studied species increased with age; with that the content of linoleic 18:2n-6 fatty acid was higher. No significant differences were found in the rate of activity of conversions of essential fatty acids - 18:2n-6 and 18:3n-3 in the long-chain PUFAs: the last one indicates the fatty acid composition of “marine” type lipids in juvenile brown trout of different age. The indexes of conversions of essential fatty acids into long-chain PUFAs, performed by the ratios 22:6n-3 / 18:3n-3 and 20:4n-6 / 18:2n-6 fatty acids, did not vary significantly during the growth of juveniles, which pointed to the residential brown trout from of the studied fish in the Orzega river. Presented ratios of fatty acids can be considered as indicators of the physiological state of juvenile salmonids, determining different life-history of brown trout forms - the presence or absence of migration.