日本近海に於ける座頭鯨の分布及び習性に就て

1. The humpbacks, Megaptera nodosa (Bonnaterre), in far east are recently remarkably diminished as in the other parts of the world. They are caught almost exclusively in the southern waters of Japan around Ogasawara Islands and the southern end of Formosa in winter, at the surface temperature 20-27°C. Whilst a number of them are found in summer as far north as Kamtebatka and Bering Sea, as Russians have reported it. Stragglers as seen anywhere.<br> 2. Both the water temperature and salinity do not seem to restrict much their migration, which of main herds presumably takes place yearly between the said southern and northern waters by a course lying far off beyond the reach of Japanese whalers from coasts. Another small group seems to migrate from the northern waters to Yellow Sea through, perhaps, Japan Sea.<br> 3. Feamles caught in these 5 years (1930-'34) are 174 in number (about 46% of total) and measure 12.4m on the average, while 205 males 12.0m. Females attain sexual maturity at the average length of about 14m, just as the No ?? th Atlantic and Arctic ones. Though small in number, those caught on the Pacific coasts of Japanese Main-land and Hokkaidô, in early summer and in late autumn, have the average length less than those caught in the southern waters. This is ?? erhaps due to the admixture of newly born calves in the catch.<br> 4. The sizes of the foetuses and the calves observed at various shore stations in the whole northern as well as southern hemisphere are all consistent with each other with respect to their growth (Fig. 7). Pairing seems to take place generally in early spring in the warm waters, followed by a period of gestation of 10 to 12 months.