| Total annual catch of tunas including skipjack in world oceans has been growing since 1970s and is now more than 4,000 thousand metric tons. Skipjack, yellowfin tuna, and bigeye tuna distributed mainly in the tropical waters are most abundant species and widely used for Sashimi, Canned tuna, and KATSUO-BUSHI etc. Albacore which is relatively small size tuna species and distributed in the sub-tropical and temperate waters is also popular in Japan as Sashimi and high grade canned tuna. Those four species composed 98% of total tuna catch. The tunas are caught by longline, purse seine, pole and line, trolling and other various gears in the world and also important fish resources for fisheries around Japan. Sword fish and bill fish are also caught by the longline.
To accomplish sustainable use of these tuna stocks, it is necessary to study the basic biology, such as ecology, migration, growth, spawning etc. Based on the information from the fisheries and the research activities, scientists assess whether or not the resources are overfished and whether catch can be increased further sustainably through discussions at Regional Fisheries Management Organizations seeking for agreement on reasonable and safe ways to utilize the resources for generations. It is also important to achieve the stable growth of fisheries on the tunas. Studies on the ecology of by-catch animals taken incidentally by tuna longline fishery, the mitigation measures of the by-catch, and the mechanism and forecast of the skipjack migration around Japan are also important research subjects of this Division.