Marine Mammal Stranding Data Collected by the Sea of Japan Cetology

Little was known on marine mammals in the Sea of Japan before 1988, when the Sea of Japan Cetology Research Group started collecting data and specimens of stranded marine mammals along the coasts. Since then, 20 to 80 stranding events have been reported each year. Data compilation has also been done based on data already published. To date more than 850 pieces of data have been collected all together. Species with more than 100 events of stranding/incidental catch are: Pacific white-sided dolphin (Lagenorhynchus obliquidens), Stejneger's beaked whale (Mesoplodon stejnegeri), and Minke whale (Balaenoptera acutorostrata). Stejneger's beaked whale, first reported in 1960 and previously believed to be extremely rare, turned out to be one of the species stranded the most frequently. Much effort has been made and various samples have been distributed to researchers working on basic biological investigations of the species. A wide range of topics are investigated, including food habit, changes in tooth shape and body color according to the age, age determination by counting GLG, distribution pattern, intra-specific mt-DNA sequence differences, contaminant burden, and parasite burden. Possibilities of the presence of the long beaked type of common dolphin (Delphinus sp.), the decline of Dall's porpoise (Phocoenoides dalli) population in the area and the increase of Risso's dolphin (Grampus griseus) are some of the important findings based on the compiled data. These findings have been achieved through the cooperation of all the members of the Sea of Japan Cetology Research Group.

Authors:

Tetsuo Hiraguchi, Kanazawa Medical University, Uchinada Ishikawa Japan
Tadasu K. Yamada, National science Museum, Tokyo
Hajime Ishikawa, Institute of Cetacean Research
Hisoka Hiruda, Marine World Uminonakamichi