OLYMPIA – No less than 137 wildlife species in Washington and Oregon – from killer whales to giant salamanders – depend one way or another on Pacific salmon for part of their diet.
Entire watersheds are nourished by salmon carcasses, packed with chemical nutrients borne inland from the sea.
For these reasons, the decline of Pacific Northwest salmon stocks has implications that extend far beyond the salmon themselves.
That is the conclusion of Pacific Salmon and Wildlife, a new report produced by a consortium of organizations with the Washington departments of Natural Resources and Fish and Wildlife playing leading roles.
Drawing from more than 500 scientific studies published over the past century, the report synthesizes decades of research to document the special role salmon play in sustaining a variety of life forms in the Pacific Northwest.
"The critical role that salmon play in the Northwest ecosystem has been documented in various ways, but that often gets lost in the current discussion about salmon recovery," said Jeff Cederholm, salmon research scientist for the Washington Department of Natural Resources and principal author of the report. "Our goal was to draw the results of all those scientific studies into a single report that illustrates what's really at stake."
The report describes native salmon as a "keystone species" that determines the fate of many others.
Of the 137 wildlife species cited in the report whose diet depends directly or indirectly on salmon, 41 are mammals (killer whales, river otters, black bear), 89 are birds (bald eagles, caspian terns, grebes), five are reptiles (turtles, aquatic garter snake) and two are amphibians (giant salamanders).
Several species, including bald eagles, rely on salmon both directly and indirectly for their dietary needs: They not only eat salmon themselves but also prey on other species that eat salmon.
Insects, such as stoneflies, caddisflies, blackflies, have their own special relationship with salmon. Many feed off salmon carcasses, then become food for juvenile salmon, completing the cycle.
"We now know that some 82 species of wildlife are consumers of salmon carcasses," said David Johnson, who conducted the study as a scientist for the Washington Department of Fish and Wildlife. "This information greatly strengthens our collective understanding of the role that salmon play in the populations of Pacific Northwest wildlife species, and how management activities such as hatcheries, harvest, and other actions can impact these species."
An example of what can happen when these interrelationships break down can be found in the collapse of the kokanee salmon run at McDonald Creek in Glacier National Park.
In 1981, McDonald Creek drew 639 bald eagles to feed on salmon carcasses, the densest concentration of eagles south of the Canadian border. When opossum shrimp were later introduced to an adjacent lake, they competed with the kokanee for zooplankton and ultimately caused the run to fail. By 1989, only 25 eagles returned to the creek area.
The report suggests that black bears may be following the same course. Although bears in Alaska are well known for their appetite for salmon, most of their cousins in Washington and Oregon appear to favor huckleberries in the higher elevations. After citing several studies on the subject, the report offers a possible explanation:
"In summary, bears have a strong relationship to salmon where they have access to them, but it appears that ... current salmon populations do not represent a predictable food supply to bears in Washington and Oregon."
Concerned that may soon be the case with many other species, the authors of Pacific Salmon and Wildlife recommend that more native adult salmon be allowed to escape the fishery and spawn. According to the report, this is necessary not only to increase the population of wild salmon but to ensure the survival many other wildlife species that depend on salmon as a source of food.
Building on that theme, the report cites numerous studies outlining the important role salmon play in cycling nutrients from the ocean to freshwater habitats. All agree that salmon, which gain 95 percent of their body weight while at sea, provide a major source of carbon, nitrogen and phosphorous for their own young and for entire ecosystems through the Northwest.
"As we recover salmon populations and their habitats, we will likely see measurable improvements in these wildlife species and in the overall health and functioning of these ecosystems," Johnson said.
Contributing to Pacific Salmon and Wildlife were scientists from the Washington departments of Natural Resources, Fish and Wildlife, and Ecology; the National Marine Fisheries Service and the U.S. Forest Service; the University of Washington and Oregon State University; and several private consultants.
Copies of the report are available by contacting WDFW at email@example.com, calling 360-902-2534, or writing to the WDFW, Habitat Program, 600 Capitol Way N., Olympia, WA 98501-1091.