El Niño changes the ocean's normal pattern of upwelling, causing the warm water to flow further south, functioning as a blanket for the cold water upwellings of nutrients from deeper within the ocean. This in turn depletes the growth of plankton thereby lessening the available food for such fish as anchovies, resulting in up to a 50% decline in their abundance. The 1982-83 episode of El Niño was probably the cause for the disappearance of more than 17 million seabirds from Christmas Island, located in the mid-Pacific Ocean. There population most likely declined due to the lack of squid and fish for the birds to feed on.

A school of anchovies, one of the many kinds of fish effected by El Niño.(Taken from www.carleton.ca)