Fatty acid composition of muscle, heart and liver lipids in Atlantic salmon, Salmo salar, at extremely low environmental temperature

Abstract

In February 1988 the seawater temperature in Hvalfjördur, W. Iceland, gradually dropped to its freezing point, −1.8°C. In a group of 2-year-old Atlantic salmon, Salmo salar, reared in seawater cages mortality started at −1.4°C. Three-year-old salmon reared under the same conditions survived at −1.7°C. During netting in this supercooled state, instantaneous freezing took place. The influence of cold acclimatization on fatty acid composition of phospholipids (PL) in muscle, heart and liver of 2-year-old Atlantic salmon was examined. The fatty acid composition of muscle and heart PL was slightly influenced by environmental temperature changes from +6.5°C to −1.4°C and the fatty acid composition of liver PL was not affected. The fatty acid pattern of PL from hearts and livers of 3-year-old salmon reared in seawater cages was studied. The samples were collected at −1.7°C. 18:1 n9 levels in liver PL were significantly higher and 22:6 n3 levels were significantly lower in the 3-year-old salmon than in the 2-year-old salmon. The salmon were fed two types of highly polyunsaturated fatty acid (PUFA)-rich diets (moist or dry pellets). The dry pellets contained significantly higher levels of n3 PUFA (20:5 n3 and 22:6 n3) than the moist pellets. In muscle the fatty acid composition of PL was markedly influenced by the fatty acids profile of the dietary lipids. Salmon fed dry pellets contained significantly lower percentage levels of 18:1 n9 and higher levels of 22:6 n3 in muscle PL than salmon fed moist pellets. The 20:5 n3 level in muscle PL was significantly lower in salmon fed dry pellets than in those fed moist pellets. No influence of dietary lipids was observed on fatty acid composition in heart and liver PL.