The northernmost haulout site of South American sea lions and fur seals in the western South Atlantic

We present estimates of the seasonal and spatial occupation by pinnipeds of the Wildlife Refuge of Ilha dos Lobos (WRIL), based on aerial photographic censuses. Twenty aerial photographic censuses were analysed between July 2010 and November 2018. To assess monthly differences in the numbers of pinnipeds in the WRIL we used a Generalized Linear Mixed Model. Spatial analysis was carried out using Kernel density analysis of the pinnipeds on a grid plotted along the WRIL. Subadult male South American sea lions (Otaria flavescens) were the most abundant pinniped in the WRIL. Potential females of this species were also recorded during half of the census. The maximum number of pinnipeds observed in the WRIL was 304 in September 2018, including an unexpected individual southern elephant seal (Mirounga leonina), and a high number of South American fur seal yearlings (Arctocephalus australis). However, there was no statistically significant difference in counts between months. In all months analysed, pinnipeds were most often found concentrated in the northern portion of the island, with the highest abundances reported in September. This study confirms the importance of the WRIL as a haulout site for pinnipeds in Brazil, recommends that land research and recreational activities occur in months when no pinnipeds are present, and encourages a regulated marine mammal-based tourism during winter and spring months. Fil: Procksch, Natália. Universidad de Vale do Rio dos Sinos; Brasil Fil: Grandi, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina Fil: Ott, Paulo Henrique. Universidade Estadual Do Rio Grande Do Sul; Brasil. Grupo de Estudos de Mamíferos Aquáticos Do Rio Grande Do Sul (GEMARS); Brasil Fil: Groch, Karina. Instituto Australis de Pesquisa E Monitoramento Ambiental. Projeto Baleia Franca; Brasil Fil: Flores, Paulo A. C.. Centro Mamíferos Aquáticos, Currently at Área de Proteção Ambiental; Brasil Fil: Zagonel, Marcelo. Universidad de Vale do Rio dos Sinos; Brasil Fil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina Fil: Machado, Rodrigo. Grupo de Estudos de Mamíferos Aquáticos Do Rio Grande Do Sul (GEMARS); Brasil Fil: Pavez, Guido. Universidad de Valparaiso; Chile Fil: Guimarães, Murilo. Universidade Federal do Rio Grande do Sul; Brasil Fil: Veronez, Maurício. Universidad de Vale do Rio dos Sinos; Brasil Fil: de Oliveira, Larissa Rosa. Grupo de Estudos de Mamíferos Aquáticos Do Rio Grande Do Sul (GEMARS); Brasil. Universidad de Vale do Rio dos Sinos; Brasil