Search

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.

Histological techniques and immunohistochemistry with antisera against insulin and somatostatin were used in a study of the identification and the distribution of endocrine pancreatic tissue in adults of four species of lampreys in British Columbia. The fine structure of the pancreatic cells of one of the species was also examined. The four species ( Lampetra ayresi, Lampetra tridentata, Lampetra macrostoma , and Lampetra richardsoni ) all possess cranial and caudal pancreatic masses and an intervening intermediate cord, but there are variations in amount and deposition of the pancreatic tissue with respect to the alimentary canal and the liver which appear to be species specific. There is also some variation in the distribution of pancreatic tissue between L. richardsoni of different stream populations. A newly identified parasitic variety of L. richardsoni in Morrison Creek, called L. richardsoni var. marifuga , usually has no cranial pancreas but has an extensive intermediate cord. The distribution of pancreatic tissue in these lampreys is of relevance to taxonomy and to variations in development of the endocrine pancreas during lamprey metamorphosis. The pancreatic tissue of all species and var. marifuga is composed of cells which are immunoreactive to either insulin or somatostatin antisera. The fine structure of cells from the cranial and caudal pancreatic tissue from L. ayresi does not vary with saltwater and fresh-water acclimation. Insulin-containing B cells and somatostatin-containing D cells are present in equal numbers in both pancreatic regions and the cells each have characteristic cytoplasmic granules. A third cell type is most abundant in the cranial pancreas but it is of unknown function.