鲤、鲢、鳙、草鱼苗最适下塘时间的研究

Optimum Time to Stock Common Carp, Silver Carp, Bighead Carp and Grass Carp Fry

在水温18.0～23.0℃条件下,鲤、鲢、鳙、草鱼苗的最适生长下塘时间为腰点出现后12～24h,最适成活下塘时间为腰点出现时至腰点出现后24h。这几种鱼适时下塘时间范围的顺序为:鲤>鳙>草鱼>鲢。电镜观察发现,鲤苗最适成活下塘时间正值皮肤上粘液细胞数量最多时。

Common carp (Cyprinus carpio L.), silveir carp (Hypo-phthalmichthys molitrix), bighead carp (Aristichthys nobilis), and grass carp (Ctenopharyngodon idella) fry were stocked into nine earthen test ponds ranging from 2.7 to 5.4m2 in surface area and varying between 0.5 to 0.7m in depth and twelve 80 mesh size cages each of 50 cm 2 50 cm×50 cm 12 or 24 hours, before, just or 12, 24, 36, 48, 60, 72, 84, 96, 108 and 132 hours after inflation of the swim bladder, respectively. The fry were reared for 14-16 days. At 18-23t, the optimum time to stock common carp, silver carp, bighead carp and grass carp fry for growth was between 12 and 24 hours after inflation of the swimming bladder and the optimum time to stock these fry for survival was the period between inflation of the swimming bladder and 36 hours after the inflation. The range of the optimum time to stock these fry was common carp>bighead carp> grass carp>silver carp. The accumulative temperatures within the optimum time to stock these fry were 60-70 and 110-130. The low survival rate and slow growth of the fry stocked long before the inflation of the swimming bladder may be due to slow development, low feeding efficiency and obstacle to cell division. The reason for the low survival rate and retarded growth rate of the fry stocked long before the inflation of the swimming bladder may be attributed to the unsuccessful transition from endogenous to exogenous nutrition. Optimum time to stock fry can be prolonged by decreased water temperature, by circulating water rich in rotifers in later incubation period, or feeding the fry with egg yolk to a certain extent.