1. Oceanic Fisheries Programme, South Pacific Commission, BP D5, 98848 Noumea, New Caledonia
2. Groupe SURTROPAC, ORSTOM, BP A5, 98848 Noumea, New Caledonia

Correspondence to: Correspondence and requests for materials should be addressed to P.L. (e-mail: Email: patrickl@spc.org.nc).

Nearly 70% of the world's annual tuna harvest, currently 3.2 million tonnes, 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, catches are highest in the western equatorial Pacific warm pool, a region characterized by low primary productivity rates¹ that has the warmest surface waters of the world's oceans (Fig. 1). Assessments of tuna stocks indicate that recent western Pacific skipjack catches approaching one million tonnes annually are sustainable². The warm pool, which is fundamental to the El Niño Southern Oscillation (ENSO) and the Earth's climate in general^{3, 4, 5}, must therefore also provide a habitat capable of supporting this highly productive tuna population. Here we show that apparent spatial shifts in the skipjack population are linked to large zonal displacements of the warm pool that occur during ENSO events⁵,⁶. This relationship can be used to predict (several months in advance) the region of highest skipjack abundance, within a fishing ground extending over 6,000 km along the Equator.