Fatty Acid Status of Freshwater Resident and Anadromous Forms of Young Brown Trout (Salmo trutta L.)

No qualitative or quantitative differences in the profiles of fatty acids (FAs) belonging to the main classes have been found between freshwater resident (Orzega River, Onega Lake Basin) and anadromous (Indera River, White Sea Basin) forms of young brown trout. Differences have been registered in the conversion rate of the food-derived 18:2ω-6 and 18:3ω-3 FAs into long-chain and physiologically active FAs: 20:4ω-6 (arachidonic) and 22:6ω-3 (docosahexaenoic). Freshwater residential form of young brown trout (parr, at 3+-age) from the Orzega River are distinguished by a higher index of 20:4ω-6/18:2ω-6. Anadromous form of young of brown trout (smolts, at 4+-age) from the Indera River have a higher ratio of essential FAs 22:6ω-3/18:3ω-3 and ω-3/ω-6 polyunsaturated FAs; the last index correlates with higher weight–length characteristics of the studied individuals.