摘要
本文利用北欧国家收集的关于海豹狩猎的唯一详细资料,并结合其它地区的统计资料,对过去一个世纪波罗的海灰海豹(Halichoerus grypus)和环斑海豹(Phoca hispida)的种群动态进行了模拟研究。以每年捕获到的海豹的性别和年龄变化为基础,建立了一个内容详尽的仿真模型。结果表明,灰海豹的数量已从本世纪初的88000～100000只下降到了70年代末的大约4000只。同期波罗的海环斑海豹种群的数量也从190000～220000只下降到大约5000只。在60年代中期,可能是由于受到有机氯农药的影响,造成了海豹的不育,使海豹种群数量的增长在随后的25年内受到了限制。因此,海豹数量的减少是人类过度狩猎的必然结果。但是目前海豹种群数量较低的原因,则是由于1965年后其生育率低造成的。
Development in the Baltic ringed (Phoca hispida) and grey seal (Halichoerus grypus) populations during the past century is reconstructed using uniquely detailed hunting records from the Nordic countries and published data on demographic parameters. A projection model was elaborated where annual variations in the composition of catches by sex and age were taken into account. Grey seals decreased from 88 000-100 000 in the beginning of the century to approximately 4000 in the late 1970s. The Baltic ringed seal population decreased during the same period from 190 000-220 000 to approximately 5000. In the mid-1960s, the remaining populations were afflicted by sterility, probably caused by organochlorines, which inhibited natural growth during a 25-years period. Thus, the decrease in seal numbers was a consequence of excessive hunting, but the present low numbers are due to lowered fertility rates after 1965.
