1. Department of Bioresource Development, Graduate School of Agriculture, Tokyo University of Agriculture, Funako 1737, Atsugi, Kanagawa 243-0034, Japan
2. Faculty of Commerce and Economics, Chiba University of Commerce, Konodai 1-3-1, Ichikawa, Chiba 272-8512, Japan
3. Taiji Whale Museum, Taiji 2934-2, Taiji, Wakayama 649-5171, Japan