CHANGES IN POSITIONAL DISTRIBUTION OF FATTY-ACIDS IN DORSAL MUSCLE TRIACYL-SN-GLYCEROLS FROM CHUM SALMON, ONCORHYNCHUS-KETA, AT SPAWNING SEASON

Positional distributions of fatty acids in dorsal muscle triacyl-sn-gl ycerols (TGs) were compared between the chum salmon, Oncorhynchus keta , caught on the coast and upstream at spawning season. The upstream sa lmon TGs contained 22:6 in the sn-1 and sn-3 positions at the concentr ations higher than the coast salmon TGs. The level of it in the sn-2 p osition was not so different between them. The proportions of 16:0 in the sn-1 and sn-3 positions were much lower in the upstream salmon. TG s than in the coast salmon TGs. The upstream salmon TGs also contained lower proportions of 20:5 in the sn-2 and sn-3 positions and of 16:1 in the sn-2 position. Such differences in positional distribution conf irmed the view that the depletion of TGs occurred unevenly during the migration from coast to upstream. The uneven depletion of TGs was foun d to depend on the position in which the fatty acids are esterified.