1. Laboratory of Marine Bioresources Chemistry, Division of Marine Life Sciences, Faculty of Fisheries Sciences; Hokkaido University; 3-1-1, Minato-cho, Hakodate, 041-8611 Japan
2. Pacific Bluefin Tuna Biology Group, Bluefin Tuna Resources Division; National Research Institute of Far Seas Fisheries; 5-7-1, Orido, Shimizu, Shizuoka, 424-8633 Japan
3. Fisheries Management and Oceanography Division; Seikai National Fisheries Research Institute; 1551-8 Taira-machi, Nagasaki, 851-2213 Japan