ESTIMATION OF SURVIVAL RATE AFTER TERMINAL MOLTING OF MALE SNOW CRAB CHIONOECETES-OPILIO

The present paper deals with survival rates per year after terminal molting and between two successive molting stages of the male snow crab Chionoecetes opilio, using 3,247 individuals collected by crab trap and Danish seine at the sea bottom with a depth range of 220 to 350 m in the Japan Sea off Kyoto Prefecture from March 1989 to November 1990. Snow crabs with a carapace width of more than 60 mm were divided into four molting stages, having a mean carapace width of 67.4, 91.2, 111.1 and 130.2 mm. The molting stage with the largest mean width (130.2 mm) was constituted only by terminal molting crabs. The three molting stages with smaller mean widths of 67.4, 91.2 and 111.1 mm, however, had two different groups comprising terminal molting crabs and non-terminal molting crabs. According to the percentage occurrences of the terminal molting crab in four molting stages at periods of soft and hard shell crabs, it was estimated that the survival rates of male crabs within a year after terminal molting and more than one year after the molt were less than 0.35-0.43 (year-1) and 0.58-0.71 (year-1), respectively.