The Docosahexaenoic Acid Content of the Lipid of Juvenile Bluefin Tuna Thunnus thynnus Caught in the Sea off Japanese Coast.

It has been known that the lipid of marine organisms are rich in n-3 polyunsaturated fatty acids such as docosahex aenoic acid (DHA), which has therapeutic effect on human physiology.1,2) However, the amounts of DHA in fish lipid varies with species, catching ground, and with sexual matu ration.3,4) There are few papers that report the comparative ly and constantly high DHA contents in muscle and orbital lipids in tuna species such as bluefin tuna Thunnus thyn nus, bigeye tuna Thunnus obesus, and bonito Euthynnus pelamis.5-7) Bluefin tuna distributing all over the seas is one of the most important fish in Japan. Light meat (ordinary muscle) is consumed as can foods, and fresh raw fillet "sushi" or "sashimi ." These traditional Japanese dishes are highly consumed despite of their high prices. On the other hand, dark meat (dark muscle) is used as pet foods. By-products are used as fish meal. There have been few other reports of bluefin tuna lipids,4,5) and none that we could find that reported the fatty acid composition of the individual organ or tissue of juvenile or premature bluefin tunas. The present paper deals with the fatty acid composition of individual tissue of juvenile bluefin tuna in comparison with that of sexually mature.4) Ecological significance of DHA occurrence is also discussed.