Migratory patterns of pelagic fishes and possible linkages between open ocean and coastal ecosystems off the Pacific coast of North America

Abstract

Abstract We review studies relevant to the migration of pelagic fishes between the coastal and open-ocean ecosystems off the subarctic coast of North America. We review the life history strategies of these migratory fish and to compare to the life history strategies of major coastal migrants. The oceanography in this region is dominated by north and south currents that provide a boundary between the offshore and coastal waters. Commercial fisheries off the west coast of North America are virtually all inshore of this oceanographic separation. Migrations for some species in these major fisheries are also north and south rather than east and west. However, exceptions occur for Pacific salmon, species associated with seamounts, and for transitional pelagic species such as tuna, squid and sharks. Three species of Pacific salmon, sockeye, pink and chum salmon, migrate along the coast in their first marine year and move off shore in the fall and winter in their first marine year. Three other species, coho salmon, chinook salmon, and steelhead trout, also migrate offshore, although they are less abundant and some stocks remain within the coastal regions. Pacific salmon species are a dominant daytime biomass in the surface waters in the offshore areas. It is known that albacore tuna and some sharks migrate between the offshore and coastal areas, but more research is needed to assess the relative importance of these migrations. Although the biomass of species on seamounts is small relative to coastal areas, the similarity in fauna is evidence that there is recruitment from coastal ecosystems.