Abstract

To clarify population structure of finless porpoises (Neophocaena phocaenoides) in Japan, a sequence of studies have been conducted: a questionnaire survey and aerial sighting surveys to obtain information on porpoise distribution, and analyses of skull morphology and mitochondrial DNA control region sequences to examine their geographic variation. The first two surveys indicated that finless porpoises are mainly distributed in five coastal regions in Japan (Sendai Bay-Tokyo Bay, Ise-Mikawa Bays, Inland Sea-Hibiki Nada, Omura Bay, and Ariake Sound-Tachibana Bay) and that occurrence of animals is rare in the other areas. The latter two analyses revealed geographic differences in the morphology and sequences among the five areas. Finless porpoises in each of the five regions are considered to belong to distinct populations.