Long-term studies that monitor changes in the abundance of pinnipeds are particularly relevant given that these long-lived species are considered to be indicators of the quality of the ecosystems around them. We report a continuous record of the total abundance by sex and age-classes of the South American sea lion (Otaria flavescens) in Cobquecura, the most important breeding colony in central Chile over a twelve-year period (2008 to 2020). We also analysed the demographic trends in South American sea lion abundance at this location. A total of 110 and 43 sea/land based and aerial censuses were performed over the studied period, respectively. The number of sea lions on land was highest in the summer months, which corresponds to the breeding season of the species. The abundance ranged from a minimum of 870 to a maximum of 4,531 individuals from sea/land-based observations, and from 796 to 4,854 from aerial censuses. This variation was mainly influenced by the number of adult females, the most abundant age-class in the colony. On the contrary, adult and sub-adult males were least abundant in the population. The highest numbers of pups were registered in February of each year, ranging from 448 in February 2009 to 1,214 in February 2017. During the study period, we estimated a finite growth rate (λ) of 1.031, suggesting an increase in the population size in the colony, especially in the number of pups. Considering Cobquecura is highly susceptible to anthropogenic disturbance, developing effective long-term protection through adequate management is critical to better conserve the South American sea lion in the most important breeding colony in central Chile.

中文翻译：

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智利中部最重要的繁殖地南美海狮（Otaria flavescens）的长期丰度动态

鉴于这些长寿物种被认为是其周围生态系统质量的指标，因此监测鳍足类动物数量变化的长期研究尤为重要。我们报告了南美海狮（Otaria flavescens) 位于智利中部最重要的繁殖地 Cobquecura，超过 12 年（2008 年至 2020 年）。我们还分析了该地区南美海狮丰度的人口趋势。在研究期间，分别进行了 110 次和 43 次海/陆基和空中普查。陆地上海狮的数量在夏季月份最高，这与该物种的繁殖季节相对应。来自海基/陆基观测的丰度范围从最少 870 到最多 4,531 只个体，来自航空普查的从 796 到 4,854 只个体。这种变化主要受成年雌性数量的影响，这是群体中最丰富的年龄等级。相反，成年和亚成年男性在人口中的数量最少。每年2月登记的幼崽数量最多，范围从 2009 年 2 月的 448 到 2017 年 2 月的 1,214。在研究期间，我们估计有限增长率 (λ) 为 1.031，表明该群体的种群规模有所增加，尤其是幼崽数量。考虑到 Cobquecura 极易受到人为干扰，通过适当的管理制定有效的长期保护对于在智利中部最重要的繁殖地更好地保护南美海狮至关重要。