Many endangered marine mammal populations are difficult to study, spread out over large areas, and capturing them for branding and research purposes would be unethical. Yet, they are in urgent need for assessment and conservation actions. We suggest collecting data from other more abundant populations of the same species, with careful consideration of body size, age at sexual maturity, and ecological conditions to produce scientifically sound best approximations of vital rates of data deficient endangered populations. The genetically distinct Baltic Sea harbour porpoise population amounts to about 500 animals and is classified as ‘Critically Endangered’ according to the IUCN red list. Data deficiency on nearly all demographic parameters have precluded systematic investigations of the relative importance of stressors affecting population viability. We took a comparative life history approach and investigated the phenotypic plasticity in somatic and demographic vital rates of seven larger, well studied North Atlantic harbour porpoise populations, enabling us to approximate the missing pieces of the life history of the Baltic population. We parameterized a stochastic, individual-based population model, and performed a population viability analysis for a range of biologically realistic parameter values and scenarios of environmental stressors. The baseline scenario was based on the most representative samples of healthy harbour porpoise populations and challenged with three different levels of bycatches. Due to high levels of endocrine disruptive contaminants observed in Baltic harbour porpoises, we also investigated the effect of a possible reduction in fecundity. Subsequently, the combined effects of bycatches and reduced fecundity were investigated in terms of population growth rate and quasi-extinction risk. The Baltic harbour porpoise population is viable in the baseline scenario without anthropogenic stressors. However, even the lowest estimated bycatch level of 7 individuals per year will lead to a population collapse to ≤50 animals with high probability (0.4–1.0) over the next century, assuming an intermediate or low (<73%) fecundity. Adult survival is of critical importance and mitigation of fishery impacts and reduction of anthropogenic disturbances in the identified main breeding areas are recommended.

中文翻译：

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多重压力源和数据缺乏的人群；比较生活史方法为高度脆弱的波罗的海港鼠海豚（Phocoena phocoena）的灭绝风险提供了新的线索

许多濒临灭绝的海洋哺乳动物种群很难研究，它们分布在大片区域，为了品牌和研究目的而捕获它们是不道德的。然而，它们迫切需要评估和保护行动。我们建议从同一物种的其他更丰富的种群收集数据，仔细考虑体型、性成熟年龄和生态条件，以产生数据缺乏的濒危种群的生命率的科学合理的最佳近似值。遗传独特的波罗的海港湾鼠海豚数量约为 500 只，根据 IUCN 红色名录，被列为“极度濒危”。几乎所有人口统计参数的数据缺乏，阻碍了对影响人口生存能力的压力因素的相对重要性的系统调查。我们采用比较生活史方法，研究了七个较大的、经过充分研究的北大西洋港湾鼠海豚种群的体细胞和种群生命率的表型可塑性，使我们能够近似波罗的海种群生活史中缺失的部分。我们参数化了一个随机的、基于个体的种群模型，并对一系列生物学上真实的参数值和环境压力源场景进行了种群生存力分析。基线情景基于健康港湾鼠海豚种群中最具代表性的样本，并面临三种不同水平的兼捕问题。由于在波罗的海港鼠海豚中观察到高水平的内分泌干扰性污染物，我们还研究了繁殖力可能下降的影响。随后，从种群增长率和准灭绝风险的角度研究了兼捕和繁殖力下降的综合影响。波罗的海港鼠海豚种群在没有人为压力源的基线情景下是可以生存的。然而，假设繁殖力中等或较低（<73%），即使是每年 7 只的最低估计兼捕水平也将在下个世纪以高概率（0.4-1.0）导致种群数量锐减至 ≤ 50 只。成鱼的生存至关重要，建议减轻已确定的主要繁殖区的渔业影响并减少人为干扰。