闽南近海尖头斜齿鲨的生殖生物学研究

The reproductive biology of the spadenose shark, Scoliodon laticaudus, from southern Fujian coastal waters

尖头斜齿鲨 (Scoliodonlaticaudus)是暖水性小型鲨鱼 ,为有胎盘胎生种类 .在闽南近海 ,其雄鱼的性成熟长度为 382～ 448mm ,雌鱼的性成熟长度为 40 5～ 46 7mm ,1 994年 5月至 1 995年 4月的周年随机采样中 ,雌鱼在群体中所占比例为5 3 0 % .雌鱼的妊娠开始于 1～ 4月 ,同年的 6～ 8月分娩 ,妊娠期为 5～ 6个月 .尖头斜齿鲨雌鱼每个子宫一次妊娠怀胚胎 1～ 1 2尾 ,其中 3～ 6尾者占 6 7 8% .雌鱼一次妊娠产仔鱼 2～ 2 4尾 ,平均 9 1尾 ,其中 6～ 1 3尾占 70 % ;5 7%的母体左右子宫内胚胎数相同 .胚胎数量随母体全长的增大而呈线性增加 .雌性尖头斜齿鲨生殖周期约为 2年 ,一生生殖 2～ 3次 ,生殖能力较低 .尖头斜齿鲨胚胎在分娩时全长 1 38～ 1 42mm ,与雌鱼性成熟长度的比为 0 30～ 0 35 ,胚胎的雌雄比为 1 1 7∶1 .同一子宫内及左右两子宫中的胚胎发育情况均基本相同 .另外还讨论了鲨鱼资源的保护和管理问题 .

The reproductive biology of spadenose shark is studied, the main objective is to provide scientific basis for resources protection and fisheries management. The main results are as follows:The size at sexual maturity is 382～448 mm in total length for males and 405～467 mm for females. Sex ratio of the adult population is 1.13∶1(♀∶♂). The pregnancy begins from January to April, the parturition occurs in June to August. The gestation is short(5～6 month). Litter size in one uterus ranges from 1 to 12, in 67.8% of specimens, there are 3～6 embryos. Litter size in two uteri ranges from 2 to 24, with a mean of 9.1, there are 6～13 embryos in 70% of specimens. The number of embryos in 57% of the females is the same. The number of embryos per litter increases with adult length. The reproductive cycle is about 2 a and the female reproduces 2～3 times in the whole life. Young are born at a size of about 138～142 mm in total length, and it is about 30%～35% of the size at maturity. The sex ratio of embryos is 1.17∶1(♀∶♂). The situation of embryonic development in the one or in both uteri is the same.The problems on resources protection and fisheries management are discussed.