(…) The finless porpoise (Neophocaena phocaenoides) is found in the Inland Sea of Japan (Kasuya and Kureha 1979), but has not previously been confirmed to occur in the southwestern part of the Sea of Japan. The Kanmon Pass connects the two seas (Fig. 1). In the waters adjacent to the pass, 19 specimens of the porpoise were collected between 1974 and 1989. This note presents information on distribution, reproduction and food habits from them.
The specimens reported here from the Sea of Japan are the first records from the southwestern part of the sea. Those taken from close to the pass imply that the distribution of the species in the two seas is not interrupted by the pass. Actually, the crew of ferry boats running across the pass have seen the porpoise (Shirakihara, unpublished). The narrow width, minimum of 0.6 km, and the strong current, maximum speed of 8.4 knots (Hydrographic Department of Maritime Safety Agency 1991), do not seem to disturb the movement of the porpoise between the two seas. (…)