Effect of natural and artificial diets on seasonal changes in fatty acid composition and total body lipid content of wild and hatchery-reared Atlantic salmon ( Salmo salar L.) parr-smolt

Abstract

Fatty acid composition of whole fish, stomach contents, gill, liver, and heart tissue, and total body lipids were determined in wild and hatchery-reared Atlantic salmon in August, November, and March–April during the year preceding their smolt out migration. The level of total body lipids was higher in reared than in wild fish. It decreased in the spring in both groups, a characteristic indicative of parr-smolt transformation. Also, the total amount of fatty acids in the selected tissues and stomach contents decreased during the winter and spring in both groups of fish. The fatty acid composition, as represented by the stomach contents, influenced the fatty acid composition of the fish. As a whole, the lipids of wild fish contained more saturates and less monoenes than those of reared fish. The proportion of the polyunsaturated fatty acid 20:5 was higher in wild than in reared fish while the 22:6 level was higher in reared than in wild fish. Only in March did the percentage of 22:6 in whole wild fish rise to the same level as in reared fish. The percentages of 22:6 and 20:5 decreased in liver and gills of wild fish in the spring: no such changes were found in reared fish.