Fujiwara M, Caswell H
Biology Department, MS34, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
Nature. 2001 Nov 29;414(6863):537-41. doi: 10.1038/35107054.
Northern right whales (Eubalaena glacialis) were formerly abundant in the northwestern Atlantic, but by 1900 they had been hunted to near extinction. After the end of commercial whaling the population was thought to be recovering slowly; however, evidence indicates that it has been declining since about 1990 (ref. 1). There are now fewer than 300 individuals, and the species may already be functionally extinct owing to demographic stochasticity or the difficulty of females locating mates in the vast Atlantic Ocean (Allee effect). Using a data set containing over 10,000 sightings of photographically identified individuals we estimated trends in right whale demographic parameters since 1980. Here we construct, using these estimates, matrix population models allowing us to analyse the causes of right whale imperilment. Mortality has increased, especially among mother whales, causing declines in population growth rate, life expectancy and the mean lifetime number of reproductive events between the period 1980-1995. Increased mortality of mother whales can explain the declining population size, suggesting that the population is not doomed to extinction as a result of the Allee effect. An analysis of extinction time shows that demographic stochasticity has only a small effect, but preventing the deaths of only two female right whales per year would increase the population growth rate to replacement level.
北大西洋露脊鲸（Eubalaena glacialis）曾经在大西洋西北部数量众多，但到1900年时，它们因被捕猎而濒临灭绝。商业捕鲸结束后，人们认为其种群数量在缓慢恢复；然而，有证据表明自1990年左右以来其数量一直在下降（参考文献1）。现在该物种个体数量不足300头，由于种群统计学随机性或雌性在广阔大西洋中寻找配偶的困难（阿利效应），该物种可能已经在功能上灭绝。利用一个包含超过10000次对通过照片识别个体的目击记录的数据集，我们估算了自1980年以来露脊鲸种群统计学参数的变化趋势。在此，我们利用这些估算值构建矩阵种群模型，以便分析露脊鲸濒危的原因。死亡率有所上升，尤其是母鲸的死亡率，导致1980 - 1995年期间种群增长率、预期寿命和平均一生繁殖事件数量下降。母鲸死亡率上升可以解释种群数量的减少，这表明该种群并非因阿利效应而注定灭绝。对灭绝时间的分析表明，种群统计学随机性的影响很小，但每年仅阻止两头雌性露脊鲸死亡就会使种群增长率提高到更替水平。
