The map above left and the figure above right show, in different ways, the historical and current distributions of spawning anadromous salmonids in western North America. The varying hues of green in the map correspond to the number of salmon species in any given area, with the darkest green corresponding to areas where six species are (or were) present, and the lightest green to areas with only one species. Barring a small interval along the coast in Alaska, the entire coastal region from southwest Alaska, through the Alaskan panhandle and British Columbia, as far south as the Pudget Sound and Olympic Peninsual of Washington was endowed with the full diversity of anadromous salmonids native to western North America, including sockeye (Oncorhynchus nerka), chum (O. keta), pink (O. gorbuscha), coho (O. kisutch), chinook (O. tshawytscha), and steelhead (O. mykiss). In addition to this area of greatest diversity, one or more salmon species occur in inland waterways of all of Alaska except the North Slope, into the southern Yukon, and throughout all but the far northeastern and some eastern regions of British Columbia. Anadromous salmon also historically spawned throughout essentially all of the Columbia River Basin of Washington, Oregon, Idaho, and British Columbia, and in coastal rivers draining areas as far south as coastal California and western slopes of the Sierra Nevada. Unfortunately for bears (and those who care about salmon) salmon runs in these southernmost region have been substantially diminished or even extirpated by the effects of dams and irrigation projects.

The map above also shows areas in North America (delineated in white) where densities of brown and grizzly bears are highest--in excess of 40 bear per 1000 square kilometers (see Bear densities). Along some parts of interior British Columbia, the densest populations of brown bears coincide with near-coastal areas that have the greatest abundance and diversity of spawning salmon; where bears can consume this nutritious food to the near exclusion of anything else from July through November. Certainly this holds true for all areas where brown bear densities are currently highest of all: greater than 100/1000 km2. Not coincidentally, these same densely-occupied areas also support physically the largest bears in North American (see Variation in bear size), no doubt because a proteinaceous and energy-rich diet of salmon promotes rapid and sustained accumulation of lean body mass (see Nutrition and Variation in bear size).

As you might expect, not all salmon are equally abundant in all areas, even where all six species spawn. As a consequence, the importance of different species to bears varies from region to region. The figure above right attempts to quantify these differences along a north (top) to south (bottom) Pacific coastal gradient. The relative local abundance and related intensity of consumption by bears is indicated by the vertical width of each colored bar, one for each species. Chinook salmon and steelhead are most abundant (and were most heavily consumed by bears) in south-coastal regions, including as far inland as central Idaho; sockeye is comparatively most heavily used farthest north and west, in southwestern Alaska; and chum, pink, and coho salmon are most abundant and heavily used by bears in between, in the Alaska archipelago and coastal British Columbia.