Salmon Key to Northwest’s Life Cycle, Studies Say
In the springtime, Indian tribes around the Northwest reverently place the bones of the first salmon of the year back in the water to ensure the species’ continued return.
But what if the fish never come back?
As salmon runs plummet, arguments for restoring them revolve around cultural and economic costs. Without the salmon, the center of the religion of many Northwest Indian tribes would be a memory. More than $1 billion in estimated economic spinoffs from commercial and sportfishing would go somewhere else every year.
But what about the biological effects? What if salmon could no longer overcome the myriad factors causing declining runs--too much fishing, dams blocking rivers, logging, grazing, development, hatcheries diluting the gene pool. Would the Northwest lose more than a symbol of courage and rebirth?
Scientists studying the issue say yes, and they are starting to measure the potential loss. Their conclusions reflect what used to be just common sense: that salmon are the very circle of life, returning to mountain streams the organic matter washed downstream to the ocean.
In life, salmon are the primary food for resident killer whales in Puget Sound. In death, their carcasses feed animals from shrews to bears, sparrows to eagles, and even insects and other fish. The decomposing flesh fertilizes the trees along the streams.
“The salmon is the one animal that penetrates the whole Northwest ecosystem, from the mountaintop where the eagle takes the carcass to feed its young, all the way out [in the Pacific Ocean] to the Japanese Current,” said Jim Lichatowich, a fisheries consultant.
A former assistant chief of fisheries for the Oregon Department of Fish and Wildlife, Lichatowich now lives in Sequim, Wash., where he is working on a book about the history of salmon management on the Columbia River. He also serves on an independent panel of scientists assessing salmon restoration.
“Wild salmon are a net energy provider, a net energy benefit, to their watersheds,” he said. “They capture that energy in the ocean and bring it back and deposit it back in the watershed.”
Some people are asking whether more wild salmon than are necessary should be allowed to return to their native streams just to reproduce another generation, because their carcasses are so important in recharging the ecosystem.
Until recently, the common sense of the ecological value of tons of salmon carcasses couldn’t be supported by science.
But now it can. Bob Bilby, an aquatic ecologist for the timber giant Weyerhaeuser Co., traced isotopes of nitrogen and carbon--two major building blocks of life--from dead salmon into insects, other fish and even the trees growing in the riparian zone along the river. His work was done on Grizzly Creek, a tributary of the Snoqualmie River in Washington.
“If you could view the system as an automobile, the structural characteristics of the system could be compared with the automobile itself--the engine, transmission, tires. The salmon provide the fuel. Without both, you are not going anywhere,” he said.
The numbers are big: 18% of the nitrogen in riparian vegetation came from salmon, 25% to 35% of the nitrogen and carbon in insects and 25% to 40% in young salmon, which eat the insects as well as the carcasses.
Jeff Cederholm, a salmon biologist for the Washington Department of Natural Resources, tossed 900 salmon carcasses from hatcheries onto eight streams on the Olympic Peninsula and compiled a list of 20 mammals and 23 birds seen feeding on them.
Besides the black bears and eagles commonly known to feed on salmon, the study found shrews, moles, squirrels, beaver, elk and blacktail deer eating the carcasses. Chickadees, nuthatches, song sparrows, hairy woodpeckers and winter wrens joined the feast.
“Based on Bob Bilby’s work and my work, there are strong indications we should be providing spawning escapement levels well beyond just replacing the populations,” Cederholm said.
The National Biological Service is setting up a study of how the Elwha River on Washington’s Olympic Peninsula will change if dams that have blocked salmon from the upper reaches since the early 1900s are removed.
“I would suggest they will probably see 10 times the food supply they do now in terms of small fish, in particular salmonoid species,” said Reg Reisenbichler, a researcher with the service.
In Puget Sound, Howard Garrett, administrator of the Center for Whale Research, worries that declining salmon populations may mean fewer resident killer whales. While transient orcas up and down the coast eat sea lions and dolphins, the resident killer whales in Puget Sound depend on salmon for 80% to 90% of their diet. That’s more than 200 pounds a day each.
In 1994 and 1995, when salmon populations were so low authorities almost cut off ocean fishing, 10 killer whales disappeared and presumably died from one group of 97 whales, Garrett said. He called it an unprecedented loss.
Lichatowich says the next big crash in salmon runs could come in about 30 years. Based on observations over the last 100 years, that’s when the natural swing of high salmon returns to low returns begins the next low part of the cycle.
“Probably a lot of salmon will survive and will make it to the next favorable period of climate and ocean conditions,” he said. “But if we continue to make the same mistakes, when we go into the following period of low productivity, I think we’ll lose a lot of salmon.”
Looking back on history, James R. Karr, a professor of fisheries, zoology, environmental health and public affairs at the University of Washington, warns that the unforeseen consequences could be the worst. He points to the ozone hole linked to refrigeration gases, the global warming associated with burning fossil fuels and the evolution of pests that are immune to pesticides.
“It is more often the things we don’t know and therefore can’t anticipate that are likely to blindside us,” he said.