Significance of 55゜S in the 'Indian Ocean Sanctuary of Whales' in relation to the distribution of marine mammals

摘要

The Symposium on Marine Mammals of the Indian Ocean was held at Colombo, Sri Lanka, 1983. At this symposium it was recommended that the Indian Ocean Sanctuary of Whales, which was established by the International Whaling Commission in 1979,should be extended as far as Antarctica over 55°S. Under such circumstances, the author has re-examined the distribution of all kinds of marine mammals. The baleen whales are distributed over 55°S, while most of smaller toothed whales are distributed in the waters north of 55°S. Pinnipeds like the baleen whales are found in the waters on both sides of 55°S, and sirenians never appear in colder waters. Therefore, the only groups which are substantially affected by the new expanded sanctuary are the baleen whales, sperm whales, medium-sized toothed whales and pinnipeds. Concerning these animals, some conservation agents such as the International Convention for the Regulation of Whaling and the International Convention for Conservation of Antarctic Seals, have taken some measures for their conservation which are already working effectively. If the requirement for the expanded sanctuary increases, the conservation measures ought to be systematized.