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In normal years, the trade winds cause colder, nutrient-rich waters to rised up to the surface. This process is called “up-welling.” When the cold water rises, it supports a tiny fish called plankton, which feed all kinds of larger fish species. During El Niño years, however, due to change in pressure and the direction of trade winds, the surface layer of warm water are thicker and prevents the usual effective up-welling by the coastal winds.
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