Studies on ovarian development and spawn type of cultured half-smooth tongue sole,Cynoglossus semilaevis

Seasonal variations of ovarian development and the relationship with Gonadosomatic index(GSI)、 hepatosomatic index(HSI) was studied in the cultured half-smooth tongue sole Cynoglossue semilaevis.The results show that ovarian development consists of phaseⅡ,Ⅲ,Ⅳ,Ⅴ,Ⅵ,then cycles to recrudescent phase II;under artifi-cial culture,most fish has phaseⅡovarium from March to May,and the oocytes begin to accumulate vitellin granulefrom June,then the whole cytoplasm is stuffed with vitellin granule ranging from September to November,sug-gesting the oocytes growth to mature,after spawning,the ovarium come to assimilative phase Ⅵ or recrudescent phaseⅡ;GSI reaches to an peak during reproduction,then dramatically drop after spawning or recrudescent phase Ⅱ while HSI significantly increases to maximum;there is only one breeding season in the half-smooth tongue sole,and it belongs to batch-spawning fish.This study enriches reproductive physiology of fish,and offers the scientific foundation for optimizing the technology of the half-smooth tongue sole artificial reproduction.