Effects of the 1983 El Nino on coastal nekton off Oregon and Washington

The 1982-83 El Nino event in the northeastern Pacific has been associated with significant changes In sea temperatures, vertical thermal structure, coastal currents and upwelling (this volume). Such physical changes may affect the species composition, abundance or availability of fishes and other nektonic animals in a variety of ways: e.g., passive advection of water and animals and active migration of nekton, resulting in changes in species composition; changes in the vertical distribution of specIes in response to warm surface waters that result in low availability near the surface, movement offshore into deeper water, or modified migration patterns; decreased productivity or availability of prey, and concomittant adverse effects on growth, reproduction or survival; and cianges in inshore-offshore environmental gradients and frontal structure that concentrate fishes in narrow bands where predation or competition may be intensified.