El Niño'S Effect on South American Pinniped Species

Abstract

Abstract Marine mammals living in the tropical upwelling ecosystem of Galapagos and Peru were severely affected by the influx of tropical warm water during the 1982/83 El Nino. The Galapagos fur seal (Arctocephalus palapapoensis) population suffered considerable mortality; the 4 youngest age classes were almost completely lost, along with 30% of the adult population. All larger males, which were territorial during El Nino, disappeared and presumably died. The Galapagos sea lion (Zalophus callfornianus wollebaeki) population lost most of the 1982 year class and had a greatly reduced birth rate in the breeding season following El Nino. High mortality was also reported for the South American fur seal (Arctocephalus australis) and the South American sea lion (Otaria byronia) on the southern coast of Peru. Periods with El Nino conditions cause a severe disruption of the food web, thus creating acute food shortage for both fur seals and sea lions.