PLASMA NONESTERIFIED FATTY-ACID PROFILES IN MALE AND FEMALE SOCKEYE-SALMON, ONCORHYNCHUS-NERKA, DURING THE SPAWNING MIGRATION

To establish if there are sex-specific differences in the utilization of specific fatty acids in salmon during migration, we monitored plasm a nonesterified fatty acids (NEFA) in male and female early-run Stuart sockeye salmon, Oncorhynchus nerka, during their spawning migration i n the Fraser River. Total plasma NEFA concentrations declined in both males and females to 60 and 40% of their respective initial levels. Pa lmitic (C-16:0), oleic (C-18:1), docosahexaenoic (C-22:6n3), and eicos apentaenoic (C-20:5n3) acids consistently represented between 66 and 7 7% of the total plasma NEFAs throughout the migration. These fatty aci ds are probably utilized as a source of energy to sustain swimming dur ing the migration. A difference in monoene levels between sexes sugges t that females utilized monoenes, particularly oleic acid, for yolk pr oduction. Fatty acid concentrations of the n6) series remained constan t in both sexes; however, a sudden increase of C-20 polyunsaturate pro portions of both the n3 and n6 series was observed at the time of gona dal maturation in both sexes. While plasma NEFAs are important as ener gy sources for migrating sockeye salmon, there is also a selective uti lization of plasma NEFAs for gonadal development and reproduction that is reflected in altered NEFA profiles of male and female fish, respec tively.