1. Japan Sea National Fisheries Research Institute, Fisheries Research Agency (FRA), Suido-cho, Chuo-ku, Niigata 951-8121, Japan
2. National Salmon Resources Center, Fisheries Research Agency (FRA), Nakanoshima, Toyohira-ku, Sapporo 062-0922, Japan
3. National Research Institute of Fisheries Science, Fisheries Research Agency (FRA), Fukuura, Kanazawa-ku, Yokohama 236-8648, Japan
4. Division of Marine Bioresource and Environment Science, Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho, Hakodate, Hokkaido 041-8611, Japan