Tracking South American Sea Lion Population Recovery in Patagonia Following Depletion From Hunting

Abstract

Populations of pinniped species, including the South American sea lion (SASL, Otaria byronia), declined sharply due to overharvesting between the 18th and 20th centuries. Although hunting ceased in the mid-20th century, recovery has been slow and variable across regions. This study updates SASL abundance and trend in central Patagonia after a 28-year gap, highlighting a significant increase from 29,479 individuals in 2004 to 90,862 in 2023, with an annual growth rate of 4.82%. There was a population expansion with the establishment of several new colonies, indicating a recolonization process similar to that observed in northern Patagonia. Social composition analysis revealed changes over time, with shifts in the proportions of age classes both in the whole study area and in several colonies. The recolonization dynamics suggest strong interconnectivity between regional stocks, supported by genetic studies. Despite recovery, current SASL abundance remains below pre-exploitation levels. Central Patagonia's high biodiversity and overlapping human activities, such as fisheries and coastal development, present conservation challenges. These findings provide critical insights into SASL recovery processes and emphasize the importance of sustainable management in marine protected areas. The study contributes to understanding pinniped population dynamics and offers valuable perspectives for conservation efforts across exploited marine mammal species.