El Niño, Interannual Variability and Fisheries in the Northeast Pacific Ocean

Abstract

In this review I describe the oceanic and atmospheric observations, physical mechanisms, and theories associated with El Niño – Southern Oscillation (ENSO) warming episodes in the tropical Pacific, and critically examine the means by which these anomalous events are believed to produce unusual conditions in the northeast Pacific. However, not all tropical ENSO episodes have a noticeable effect at higher latitudes. Also, because of anomalous local atmospheric forcing, significant warmings, strong coastal currents, and high sea levels along the west coast of North America can occur in years during which there are no tropical ENSO episodes. The possible impacts of ENSO-induced changes and of other interannual fluctuations in the northeast Pacific on various fisheries are described. Such impacts include changes in the migration routes of the bluefin tuna (Thunnus thynuus) and Fraser River sockeye salmon (Oncorhynchus nerka), increases in the Pacific herring (Clupea pallasi) recruitment, earlier return times for the Bristol Bay sockeye salmon, and increases in the weight of mature Fraser River sockeye several years after a local warming event.