Suitable habitat for marine mammals during austral summer in San Jorge Gulf, Argentina

Abstract

The San Jorge Gulf (SJG) is an important oceanographic region due to the influence of two tidal fronts, being one of the most productive sectors and with greater marine biodiversity in the Argentine Sea. The aim of this study was to identify which oceanographic variables best explained the presence of marine mammals and to explore the overlap of the predicted richness with the frontal areas of the SJG during the austral summer. The potential distribution of 9 species ( Balaenoptera sp., Cephalorhynchus commersonii , Globicephala melas , Grampus griseus , Lagenorhynchus australis , L. obscurus , Mirounga leonina , Orcinus orca , Otaria flavescens ) was modeled with Maxent using 6 environmental variables (bathymetry, seafloor slope, distance to the coast, distance to the frontal area, sea surface temperature and chlorophyll a concentration). Marine mammals were found closer to the frontal area than expected by chance (9.48 km and 13.34 km, respectively). Bathymetry, distance to the coast and seafloor slope were the most important variables in the distribution of all the species. Balaenoptera sp., G. melas , G. griseus , L. australis and O. orca showed a coastal distribution (<10 km), mainly in the northwest of the gulf. The distribution of M. leonina , O. flavescens and C. commersonii followed the isobaths of 80 m, while L. obscurus evenly distributed throughout the gulf. In general, the environmental variables that influence the distribution of these species agreed with those found in previous studies from other locations. The area of high predicted richness was 75% overlapped with the frontal areas located in the northwest and southeast of the gulf. This work provides baseline information for designing future samplings that could explain the influence of the processes and the seasonal variation of the distribution of the marine mammals of the SGJ.