Resumen del producto

The population of California sea lions (Zalophus californianus) in the Gulf of California has decreased 65.2% between 1991 and 2019, in relation mainly to long-term sea surface warming. Los Islotes is the only breeding colony that had not show a decline. The goal of this study was to estimate the abundance and trophic breadth of this colony and its relationship with the satellite sea surface temperature (SST) recorded between 2013-2018. Monthly colony counts were performed and stable isotopes of nitrogen (d 15N) and carbon ( d13C) in the hair of 158 previously weighted pups were analyzed in order to obtain interannual isotopic areas of adult females. By considering all age classes, abundance was not significantly distinct between breeding seasons (summer); however, it was significantly different throughout all months of the year, showing a decrease in this colony for the first time: 23% from 2013 to 2018. A 50-60% decrease in pup abundance was observed in the region that had an impact on prey availability and, consequently, female fecundity. There was a significant inverse correlation between average pup weight and SST anomalies, showing that their body condition was affected during the warming of 2014 and 2018. Adult females showed inter-annual differences in isotopic areas, evidencing different lengths of their feeding trips as a sign of resilience during adverse environmental conditions. We evidence vulnerability by sea lions from Los Islotes, in presence of warm anomalies in the regional foraging grounds.

Palabras clave: Trophic ecology; sea surface temperature anomalies

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