| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1988: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1987: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1986: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
To improve the knowledge of biology of the small cetaceans, the present study was carried out. Teeth, sexual organs, stomach contents, skulls and internal organs were collected from the dolphins at several fish markets. These samples were brought back to the laboratory and were analyzed from the morphological, ecological, biochemical aspects.
Several thousands Dall's porpoises, Phocoenoides dalli, were incidentally taken by the Japanese salmon gillnet every season and about 20,000 porpoises have been annually caught by the harpoon fishery. Thus, the population study of the species was the most important issue in the national and international research projects on the small cetaceans. From the present study, it is clear that there are at least the following six populations of the species in the North Pacific: Bering Sea, Japan-Okhotsk Sea, Off Sanriku, northwestern North Pacific,northeasterm North Pacific and off the Pacific coast of America. Stock estimation and reproductive rate of the species are analyzing in each population. Modeling of population management is conducted using the information of food items, feeding rate, age composition, population size and so on. In other three species of Lagenorhynchus obliquidens. Delphinus delphis and Globicephala macrorhynchus, the separate two population (northern and southern type) are found in the Japanese waters based on the morphological and ecological information. From these findings, new population management system will be constructed in the near future.
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