THE MATURITY OF JAPANESE MITTEN CRAB ERIOCHEIR JAPONICUS DE HAAN IN OHBISO RIVER, CHIBA

Abstract

The mitten crab Eriocheir japonicus inhabits the river. In Ohbiso River, mature crabs with high gonad index [GI=(gonad weight) / (carapace width)^3×10^5>0.48] appear in November, presenting a wide abdomen (AI=abdomen width/abdomen length>0.88), moving to the brackish water region for mating and reproduction. Immature crabs have a narrow abdomen (AI<0.88) and remain in the fresh water region of the river.