EFFECTIVENESS OF PROHIBITION OF TAKING SO FT-SHELL MALE SNOW CRAB CHIONOECETES-OPILIO IN THE SEA-OF-JAPAN

The present paper investigates the carapace width compositions of soft -shell males Chionoecetes opilio caught by Danish seiners and the effe ctiveness of prohibition of catching soft-shell males in order to keep the optimum sex ratio at 0.47 (ratio of the number of terminal molt m ales with hard-shell to the number of multiparous females). The sex ra tio was estimated to be 0.37 in the present fishing intensity for mult iparous females, hard-shell and soft-shell males in the Sea of Japan. Soft-shell males were mainly less than 100 mm carapace width and non-t erminal molt regardless of carapace size, and terminal or non-terminal molt cannot mate with multiparous females, It seems that the abundanc e of recruitment to functional maturity males with hard-shell decrease s due to the catch of soft-shell males. It was ascertained that the op tium sex ratio would be maintained at the present fishing condition fo r hard-shell males with fishing coefficient 0.5 year(-1) decreased eff ort for multiparous females and prohibition of soft-shell males catch.