Population analysis of small cetaceans

为了提高对小型鲸类生物的认识，开展了本研究。在几个鱼市收集了海豚的牙齿、性器官、胃内容物、头骨和内脏。将这些标本带回实验室，从形态学、生态学、生物化学等方面进行分析。每个季节都有数千只海豚偶然被日本鲑鱼刺网捕获，每年约有20,000只海豚被鱼叉渔业捕获。因此，该物种的种群研究是国内和国际小型鲸类研究项目中最重要的问题。从目前的研究中可以清楚地看出，北太平洋至少有以下六个种群：白令海、日本-鄂霍次克海、三陆外、北太平洋西北部、北太平洋东北部和美国太平洋沿岸。对各种群的种群估计和繁殖率进行了分析。利用食物种类、摄食率、年龄构成、种群规模等信息对种群管理进行建模。在其他三种斜吻鹬中。根据形态学和生态学资料，在日本海域发现了两个独立的种群（北型和南型）。根据这些研究结果，将在不久的将来建立新的人口管理系统。

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.