Ecosystem Overview: Pacific North Coast Integrated Management Area (PNCIMA)

Abstract

This report provides an overview of physical and biological ecosystems in the Pacific North Coast Integrated Management Area (PNCIMA). PNCIMA is one of several Large Ocean Management Areas created for ecosystem based management of human use in marine areas by Fisheries and Oceans Canada. PNCIMA includes the Pacific coast of British Columbia from the Canada-Alaska border in the north to Brooks Peninsula on NW Vancouver Island and Quadra Island and Bute Inlet in the south; from the outer limit of the continental slope in the west to the coastal watersheds in the east.

PNCIMA is characterized by steep and rugged coastal mountains, abundant offshore islands, a coastline dominated by rocky shores with few sand and gravel beaches, valleys and fjords that extend to the ocean floor, and a glacially scoured continental shelf with cross cutting troughs. The Pacific Ocean moderates the climate, resulting in warm wet winters and cool summers. PNCIMA is located in a transition zone between two areas, one dominated by Alaska Coastal Current downwelling (north), and the other by California Current upwelling (south). PNCIMA’s semi-enclosed basin, varied bottom topography, and freshwater input set it apart from other areas of the North American west coast. The troughs and steep edges influence, and likely enhance, plankton and fish production. Strong tidal mixing in the narrow passes and channels enhances productivity around the periphery.

The overall trophic structure of the PNCIMA region appears to be relatively robust to reduction or elimination of single components in the food web, as long as other species occur within the same functional group. However, trophic pathways to individual species may be more constrained; it is unknown which species may be critically sensitive to the reduction or elimination of other species. Existing data suggests that the trophic structure is largely controlled by “bottom-up” forcing.

The ecosystem receives a large biomass of migratory species: stop-over migrants, such as Pacific salmon and marine migratory birds; destination migrants such as whales; and environmental migrants such as pelagic zooplankton and fish that enter PNCIMA when conditions are unusually warm. Migrants provide an input of energy and food, but also can export energy from the system, as in Pacific salmon’s transfer of energy and nutrients from marine to terrestrial coastal ecosystems.

Habitat use for many large and/or commercial marine species found within PNCIMA is summarized, including significant nearshore and biologically productive pelagic habitats. Eleven appendices detail our current state of knowledge for the geology, meteorology and climate, physical and chemical oceanography, plankton, marine plants, invertebrates, groundfish, pelagic fishes, Pacific salmon, marine mammals and turtles, and sea birds in PNCIMA.