1. Department of Aquatic Bioscience and Industry; Graduate School of Bio-Industry; Tokyo University of Agriculture; Abashiri 099-2493 Japan
2. Department of Biomedical Sciences; Graduate School of Veterinary Medicine; Hokkaido University; Sapporo 060-0818 Japan
3. Research Center for Zoonosis Control; Hokkaido University; Sapporo 001-0020 Japan
4. NPO Marine Wildlife Center of Japan; Abashiri 093-0042 Japan