Geographical and species differences of fatty acid components of small pelagic fishes, micronekton, and squids in the northwestern pacific

Geographical and species differences in fatty acid composition were evaluated among 546 specimens of small pelagic fish, micronekton, and squid in the Northwestern Pacific. For all species except for four micronekton species, the dominant fatty acid was docosahexaenoic acid (DHA). The ratios of ω3 to ω6 fatty acids and DHA to eicosapentaenoic acid (EPA) differed among species and organisms. ω3:ω6 and DHA:EPA were generally lower in micronekton than in squids and small pelagic fishes. The ω3:ω6 values in the northeastern area was higher than that in the southwestern area, meanwhile the DHA:EPA values in the northeastern area was lower than that in the southwestern area. Geographical differences in fatty acid components, DHA:EPA, and ω3:ω6 could have been caused by environmental factors as well as by regional differences in the quality and quantity of phytoplankton-produced organic matter. Non-metric multidimensional scaling of the main fatty acid components showed clear species and geographical differences. A permutational multivariate analysis of variance revealed significant differences among small pelagic fishes, micronekton, and squids. These results indicate that fatty acid analysis can be used to understand the ecology and ecosystem roles of various species.