Increase in cetacean and seabird numbers in the Canal de Ballenas during an El Niño-Southern Oscillation event

El Niño-Southern Oscillation (ENSO) events cause a decline in upwelling-based primary productivity throughout the California Current system and southern Gulf of California. However, in the Canal de Ballenas, central Gulf of California, primary productivity is based on tidal mixing and appears unaffected by ENSO events. Between the ENSO year of 1983 and the anti-ENSO year of 1985 we censused 4 piscivores (Bryde's whale Balaenoptera edeni; common dolphin Delphinus delphis; blue-footed booby Sula nebouxii and brown booby S. leucogaster) and 3 planktivores (fin whale B. physalus; black storm-petrel Oceanodroma melania; and least storm-petrel O. microsoma). For all species the number of individuals sighted per hour declined by 77 to 94 % over the 3 yr period. This suggests that during ENSO events the Canal de Ballenas may serve as a refugium of high productivity and prey abundance for these highly mobile marine animals.