Association between fatty acid signature and growth rate of larval Pacific bluefin tuna in two major spawning grounds

Abstract

Fatty acid composition and total fatty acids of field-caught Pacific bluefin tuna (PBF) Thunnus orientalis larvae were investigated to identify relationships between spawning ground, physiological condition, and growth rate. Multivariate statistical analyses revealed that both growth rate and environmental conditions at spawning grounds were substantially associated with variations in fatty acid compositions. Fast-growing larvae typically contained more α-linolenic acid and 22:5n-3, which are important as metabolic precursors of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Larval PBF fatty acid compositions differed by spawning ground; larvae caught around the Nansei Islands contained more 15:0, 17:0, 19:0, and 22:5n-6, and less EPA and arachidonic acid (ARA) than those from the Sea of Japan. Differences in larval odd-numbered fatty acid compositions might indicate different degrees of dependence on microbial loop energy supply between spawning grounds. Environments subject to sudden changes, such as those in water temperature and prey density in the Sea of Japan, might cause variability in fatty acid profiles, including extremely low %DHA. We suggest that continuous food intake and subsequent fatty acid catabolism for energy generation would be needed to facilitate fast growth.