Pace Richard M, Corkeron Peter J, Kraus Scott D
Northeast Fisheries Science Center Woods Hole MA USA.
New England Aquarium Boston MA USA.
Ecol Evol. 2017 Sep 18;7(21):8730-8741. doi: 10.1002/ece3.3406. eCollection 2017 Nov.
North Atlantic right whales ( Müller 1776) present an interesting problem for abundance and trend estimation in marine wildlife conservation. They are long lived, individually identifiable, highly mobile, and one of the rarest of cetaceans. Individuals are annually resighted at different rates, primarily due to varying stay durations among several principal habitats within a large geographic range. To date, characterizations of abundance have been produced that use simple accounting procedures with differing assumptions about mortality. To better characterize changing abundance of North Atlantic right whales between 1990 and 2015, we adapted a state-space formulation with Jolly-Seber assumptions about population entry (birth and immigration) to individual resighting histories and fit it using empirical Bayes methodology. This hierarchical model included accommodation for the effect of the substantial individual capture heterogeneity. Estimates from this approach were only slightly higher than published accounting procedures, except for the most recent years (when recapture rates had declined substantially). North Atlantic right whales' abundance increased at about 2.8% per annum from median point estimates of 270 individuals in 1990 to 483 in 2010, and then declined to 2015, when the final estimate was 458 individuals (95% credible intervals 444-471). The probability that the population's trajectory post-2010 was a decline was estimated at 99.99%. Of special concern was the finding that reduced survival rates of adult females relative to adult males have produced diverging abundance trends between sexes. Despite constraints in recent years, both biological (whales' distribution changing) and logistical (fewer resources available to collect individual photo-identifications), it is still possible to detect this relatively recent, small change in the population's trajectory. This is thanks to the massive dataset of individual North Atlantic right whale identifications accrued over the past three decades. Photo-identification data provide biological information that allows more informed inference on the status of this species.
北大西洋露脊鲸（Müller，1776年）给海洋野生动物保护中的数量及趋势估计带来了一个有趣的问题。它们寿命长、个体可识别、高度洄游，且是最稀有的鲸类之一。个体每年被重新观测到的概率不同，主要是因为在一个大地理区域内的几个主要栖息地停留时间不同。迄今为止，已得出了一些数量特征描述，这些描述使用了对死亡率有不同假设的简单核算程序。为了更好地描述1990年至2015年间北大西洋露脊鲸数量的变化情况，我们采用了一种状态空间模型，该模型基于乔利 - 西伯关于种群进入（出生和迁入）的假设，针对个体重新观测历史，并使用经验贝叶斯方法进行拟合。这个分层模型考虑了个体捕获异质性的影响。除了最近几年（重新捕获率大幅下降时），该方法得出的估计值仅略高于已发表的核算程序得出的结果。北大西洋露脊鲸的数量从1990年估计中位数270头以每年约2.8%的速度增长，到2010年达到483头，然后在2015年下降，最终估计为458头（95%可信区间为444 - 471）。估计2010年后种群数量呈下降趋势的概率为99.99%。特别令人担忧的是，成年雌性相对于成年雄性存活率降低导致了两性数量趋势出现分化。尽管近年来存在生物方面（鲸鱼分布变化）和后勤方面（用于收集个体照片识别信息的资源减少）的限制，但仍有可能检测到种群数量轨迹中这一相对近期的小变化。这得益于过去三十年积累的大量北大西洋露脊鲸个体识别数据集。照片识别数据提供了生物学信息，有助于对该物种的状况进行更明智的推断。
