Plasma nonesterified fatty acid profiles in male and female sockeye salmon, (<i>Oncorhynchus nerka</i>), during the spawning migration

Abstract

To establish if there are sex-specific differences in the utilization of specific fatty acids in salmon during migration, we monitored plasma nonesterified fatty acids (NEFA) in male and female early-run Stuart sockeye salmon, Oncorhynchus nerka, during their spawning migration in the Fraser River. Total plasma NEFA concentrations declined in both males and females to 60 and 40% of their respective initial levels. Palmitic (C16:0), oleic (C18:1), docosahexaenoic (C22:6n3), and eicosapentaenoic (C20:5n3) acids consistently represented between 66 and 77% of the total plasma NEFAs throughout the migration. These fatty acids are probably utilized as a source of energy to sustain swimming during the migration. A difference in monoene levels between sexes suggest that females utilized monoenes, particularly oleic acid, for yolk production. Fatty acid concentrations of the n6) series remained constant in both sexes; however, a sudden increase of C20 polyunsaturate proportions of both the n3 and n6 series was observed at the time of gonadal maturation in both sexes. While plasma NEFAs are important as energy sources for migrating sockeye salmon, there is also a selective utilization of plasma NEFAs for gonadal development and reproduction that is reflected in altered NEFA profiles of male and female fish, respectively.