Changes in the feeding ecology of South American sea lions on the southern Brazilian coast over the last two decades of excessive fishing exploration

In the last decades, an increasing fishing effort and a decreasing trend in fish catches have been observed in southern Brazil. Considering that marine mammals and fisheries usually compete for the same resources, it is reasonable to presume that the feeding ecology of these predators is affected by the current scenario. To evaluate this hypothesis, long-term variation in the diet of the South American sea lion (Otaria flavescens) relative to fisheries exploitation was analyzed for two periods (1993–2003 versus 2004–2014). The degree of overlap between the relative biomass of the sea lions’ diet and the target species of six types of local fishery was analyzed. An increase in prey overlap between sea lions and fisheries was observed in the more recent sampling period, along with an increase in prey diversity, richness, and niche breadth of the sea lions’ diet. These results suggest that the overfishing scenario could partly explain the modified feeding ecology of the sea lions. In this context, we recommend a review and better regulation of the current fishing effort in the region, which we believe will be an important step to maintain the fish stocks and minimize the impact of fishing on marine top predators. Fil: Machado, Rodrigo. Universidade Federal do Rio Grande do Sul; Brasil Fil: Rosa de Oliveira, Larissa. Universidade Do Vale Do Rio Dos Sinos; ; Brasil Fil: Ott, Paulo Henrique. Universidade Estadual Do Rio Grande Do Sul; ; Brasil Fil: Denuncio, Pablo Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Haimovici, Manuel. Universidade Federal do Rio Grande do Sul; Brasil Fil: Cardoso, Luis Gustavo. Universidade Federal do Rio Grande do Sul; Brasil Fil: Danilewicz, Daniel. Universidade Estadual de Santa Cruz; Brasil Fil: Moreno, Ignacio Benites. Universidade Federal do Rio Grande do Sul; Brasil Fil: Borges-Martins, Márcio. Universidade Federal do Rio Grande do Sul; Brasil