Plasma non-esterified fatty acid profiles in wild Atlantic salmon during their freshwater migration and spawning

Total plasma non-esterified fatty acid (NEFA) levels increased significantl y in adult Atlantic salmon during the first months of their upstream migrat ion and spawning in the Exploits River, Newfoundland. Canada. The highest l evels occurred in May and were 5467 +/- 270.43 nmol ml(-1) for females and 4617 +/- 334.70 nmol ml(-1) for males. Significantly higher levels were mai ntained by females compared with males for most of the upstream migration. Between August and October, total plasma NEFA levels declined by 61% in fem ales but only 23% in males. The decline in plasma monounsaturated and polyu nsaturated fatty acid levels accounted for 74% of the loss of NEFAs in fema les. Specific plasma NEFAs such as 16 : 0 (palmitic), 16 : 1 (palmitoleic), 18 : 1n9 (oleic) and 10 : 5n3 (eicosapentaenoic acid) differed significant ly between males and females during migration and spawning. The mean gonado somatic index (I-G) values of females in May and just prior to spawning wer e 0.37 +/- 0.01 and 10.25 +/- 0.32, respectively. The rapid decline in the plasma NEFA content of females coincided with the largest increase in their I-G (1.85 +/- 0.02-10.25 +/- 0.32). Corresponding I-G values for males wer e 0.34 +/- 0.01 in May and 3.33 +/- 0.78 prior to spawning. Plasma NEFA lev els of spent salmon did not differ between sexes and were significantly low er than those of salmon preparing to spawn. (C) 1999 The Fisheries Society of the British Isles.