EL-NINO SOUTHERN OSCILLATION AND TUNA IN THE WESTERN PACIFIC

Nearly 70% of the world's annual tuna harvest, currently 3.2 million t onnes, comes from the Pacific Ocean. Skipjack tuna (Katsuwonus pelamis ) dominate the catch. Although skipjack are distributed in the surface mixed layer throughout the equatorial and subtropical Pacific, catche s are highest in the western equatorial Pacific warm pool, a region ch aracterized by low primary productivity rates' that has the warmest su rface waters of the world's oceans (Fig. 1). Assessments of tuna stock s indicate that recent western Pacific skipjack catches approaching on e million tonnes annually are sustainable(2). The warm pool, which is fundamental to the El Nino Southern Oscillation (ENSO) and the Earth's climate in general(3-5), must therefore also provide a habitat capabl e of supporting this highly productive tuna population. Here we show t hat apparent spatial shifts in the skipjack population are linked to l arge zonal displacements of the warm pool that occur during ENSO event s(5,6). This relationship can be used to predict (several months in ad vance) the region of highest skipjack abundance, within a fishing grou nd extending over 6,000 km along the Equator.