A legal minimum size of 90 mm in carapace width has been enforced for male snow crab Chionoecetes opilio fishery in the western Sea of Japan. And the fishing periods for hard-shelled and soft-shelled males are currently limited from 6 November to 20 March of the following year and from 21 December to 20 March of the following year, respectively. Under these conditions, the estimated sex ratio （the number of terminal molt males with hard shell to the number of multiparous females） was 0.35, which was lower than the ratio of 0.49 of virgin stock. In this study, we investigated the fishing intensity for soft-shelled males needed to obtain the sex ratio of virgin stock.
It was estimated that the opening date of the fishing period for soft-shelled males should be 1 March, if the terminal date and the legal size remain unchanged, and if the legal size is set to a carapace width of 110 mm, the opening date should be 29 January. As a matter of course, it is desirable to reduce by half the current fishing intensity for females and to maintain the sex ratio of virgin stock. In order to satisfy these regulations, however, it will be necessary not to only limit the capture of soft-shelled males but to take some measures such as enlargement of the legal minimum size and shortening of the fishing period for hard-shelled males.