Abstract
We examined 44 finless porpoises stranded or caught incidentally in Mikawa Bay, Japan, from October 2002 to July 2007. We analyzed date, locality, body length and sex from an additional 105 stranded or by-caught specimens reported in previous studies as well. We found that these finless porpoises in Mikawa Bay were born mainly in April to June, with body lengths of around 80 cm. The sex ratio of stranded animals less than 120 cm in body length was nearly even, but males outnumbered females in larger specimens: the ratio of males to females was more than 1.6. The number of stranded animals increased in April–June and October–December. Calves with body lengths of around 80 cm were found only in April and May, while most of the animals with body lengths of 100–140 cm were collected in October to December. Stranding localities changed seasonally. Strandings occurred along the entire coast of the bay from spring to autumn, while records were rare in the innermost area of the bay in winter.
