Bryde's whale (Balaenoptera edeni) in the southwestern Gulf of California: Relationship with ENSO variability and prey availability

Interannual changes in the occurrence of Bryde's whale (Balaenoptera edeni) have been observed in La Paz Bay (southwestern Gulf of California, Mexico) over the last 20 years. We suggest that these changes could be driven by natural fluctuations in food resources that are related to climate variability. We compared monthly Bryde's whale occurrence in La Paz Bay from 1988 to 2006 to climate variability at seasonal and interannual time scales and its effect on prey availability. The results showed that Bryde's whales do not have a well-defined pattern of seasonal occurrence; however, large numbers of whales were consistently recorded during La Nina conditions when the Gulf of California sardine population is distributed further south within the gulf. In contrast, fewer whales were recorded during El Nino and neutral conditions. This indicates that changes in the occurrence of Bryde's whales at La Paz Bay are driven by the El Nino-Southern Oscillation interannual variability and are probably mediated by their prey availability.