Spatial analysis of yellowfin tuna (Thunnus albacares) catch rate and its relation to El Niٌo and La Niٌa events in the eastern tropical Pacific

Spatial and temporal variations in catch-per-unit-effort (U) were analyzed under extreme conditions of sea-surface temperature during the warm years of 1982 and 1987, and cold years of 1988 and 1989. Distribution of U revealed high-density patches in areas with greatly ranging temperatures and temperature anomalies up to 2.5°C. These patterns were observed mainly in the south of Mexico, near the Costa Rica dome, on the South American coast, and in the equatorial zone between 0° and 15°N. These results suggest that temperature is not a determining factor in the distribution of tuna, and that the high biological productivity of certain areas in the eastern tropical Pacific is more important.