摘要
为了评估里海海豹这个物种年度幼崽生殖情况及新生幼崽的被自然捕食情况,2005和2006年2月在哈萨克斯坦领海的冬季冰原对里海海豹进行了航空调查。据估计,2005年幼崽生殖数量为21063头,2006年为16905头(每年出生在俄罗斯领土上的里海海豹幼崽估计数包括在内)。大约20 000头雌性里海海豹的繁殖种群数量大大低于所公布的20世纪80年代末以来的估计数。鹰是里海海豹幼崽的头号捕食天敌。尽管2005年,商业破冰船路线没有穿越里海海豹幼崽集中的区域,但是在2006年,商业破冰船路线穿越了这些区域。我们的发现对制定该物种的保护策略有着重要的意义。自然死亡率、捕食者造成的损失,以及更为重要的是,现有的捕猎限额显著超过了里海海豹种群的补充量。人为的致死行为应当得以控制,以避免该物种的进一步减少。
Aerial surveys of Caspian seals on the winter ice field in Kazakhstan territorial waters were carried out in February 2005 and 2006 to assess the annual pup production for the species and natural predation on newborn pups.Estimated pup production was 21 063 in 2005 and 16 905 in 2006 (including an estimated figure for pups bom in Russian territory in each year).The breeding population size of approximately 20 000 females is much less than published estimates from the late 1980s.Eagles were the principal natural predators of pups. Commercial icebreaker routes passed through areas of dense pup concentrations in 2006,although not in 2005.Our findings have important implications for the development of conservation strategies for the species. Natural mortality,loss to predators,and,more important,the current hunting quota substantially exceed the recruitment of the Caspian seal population. Anthropogenic sources of mortality should be managed to avoid further declines in the species.