Tamaki Shimose

Session 3, Talk 1, 18/1/16 @ 1530 hrs

Pacific bluefin tuna Thunnus orientalis occurs in tropical to temperate waters in the Pacific Ocean, and main distribution range is in the North Pacific. Ontogenetic habitat shift and seasonal movement of the species are reviewed with the information of size (fork length), age (Shimose et al. 2009), and gonadal maturation (Ashida et al. 2015, Okochi et al. 2016 etc.) which was determined by using specimens of Japanese commercial catch. A ge-0 bluefin (ca. <60 cm) occur in coastal areas of Japan from July to next spring. After reaching age-1 (ca. >60 cm), core distribution area moves northward in summer and southward in winter, and some of age-1 bluefin migrate to the eastern North Pacific feeding ground. Spawning was confirmed from age-3 (ca. 110 cm) in the Sea of Japan spawning ground during mid-June to early-August, and nearly 100% of bluefin in this specific region were mature at age-4 (ca. 130 cm). Adult bluefin also migrate to another main spawning ground located from around Okinawa (southernmost islands in Japan) to off Philippines only during the spawning season mid-April to early-July. The first occurrence of maturity in this region is age-6 (ca. 170 cm), but main component is age-8–20 (ca. 200–250 cm). During non-spawning season, some adults occur around the waters off northern Japan and some probably migrate to other areas. Growth rate decreases after age-10. Average asymptotic length, body weight, and maximum life span are estimated to be ca. 250 cm, 300 kg, and 28 years, respectively.

Contact:  T. Shimose, Seikai National Fisheries Research Institute, Fisheries Research Agency, Japan, This email address is being protected from spambots. You need JavaScript enabled to view it.