日本海ズワイガニ漁業における "水ガニ" 漁獲禁止の有効性

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The present paper investigates the carapace width compositions of soft-shell males Chionoecetes opilio caught by Danish seiners and the effectiveness 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 males with hard-shell to the number of multiparous females). The sex ratio was estimated to be 0.37 in the present fishing intensity for multiparous females, hard-shell and soft-shell males in the Sea of Japan.Soft-shell males were mainly less than 100mm carapace width and non-terminal molt regardless of carapace size, and terminal or non-terminal molt cannot mate with multiparous females. It seems that the abundance of recruitment to functional maturity males with hard-shell decreases due to the catch of soft-shell males.It was ascertained that the optium sex ratio would be maintained at the present fishing condition for hard-shell males with fishing coefficient 0.5 year-1 decreased effort for multiparous females and prohibition of soft-shell males catch.
1997-01-15