Fish tend to be less abundant in the warmer water.
Easterly trade winds develop along the equator due to pressure patterns over the warm subtropical waters of the Pacific. Off the northwest coast of South America these winds cause surface water to move west, away from the land, which induces upwelling of cold water from the deeper ocean. The deep water is rich in oxygen and nutrients. Plankton thrives, attracting a great variety of sea life, making this one of the world s richest fishing areas. The Southern Oscillation has been shown to see-saw from one extreme to another over the course of years.