Now, studies by Weyerhaeuser Co. fish biologist Bob Bilby have shown that spawned-out salmon are concentrated storehouses of nutrients, playing a critical role in sustaining life along and within streams. When salmon are at sea, they pick up nitrogen and carbon not found in native, freshwater organisms. Bilby and his team were able to trace those nutrients as they made their way through the food chain.
In tributaries to Washington's Snoqualmie River, where coho salmon runs are still relatively healthy, Bilby found that 18 percent of the nitrogen in streamside vegetation came from spent salmon and their eggs. The dead fish provided some 15 to 30 percent of the nitrogen and carbon in insects, he discovered, and 25 to 40 percent of the two nutrients in young trout and salmon.
"We thought we would see a sign, but we had no idea it would be so large," says Bilby.
Dwindling salmon runs and the hatchery practice of removing spawning fish from streams conspire to rob ecosystems of these nutrients, Bilby's studies suggest. His work has caught the attention of Washington fishery managers, who plan to launch a pilot project this fall to place salmon carcasses from hatcheries in some of the state's rivers and streams.
"It's almost like Mother Nature sent her soldiers out to sea to get the nutrients to feed the watershed," says Ross Fuller, a division manager for the state Department of Fish and Wildlife's hatcheries program. "What we're trying to do now is to get back to that result."
Putting the scheme into action will not be as easy as it may seem. Strict regulations govern how state officials handle the more than 500,000 fish that return to Washington's hatcheries each year. For example, federal law dictates that fish that have been injected with antibiotics must be disposed of. Most of the fish, however, are sold by contract for uses ranging from prison food to the production of fish meal.
State officials are currently developing guidelines to control how carcasses will be dispersed. Issues they must address include ensuring that the dead salmon are free of disease and that property owners near the targeted streams are told about the program.
Most carcasses probably will be placed directly into the water, says Stephen Evans, wild-stock restoration coordinator for the state's hatchery program. Officials have not yet determined which streams will receive the fish, but will target those with low nitrogen levels and with agreeable streamside land owners.
So far, Evans says, the plan has enjoyed widespread support. But he, Bilby, and others emphasize that the program is no substitute for the ultimate goal of restoring healthy runs of wild salmon.
"There's no way we will have enough biomass available to simulate historical levels," Evans says. "Our hope is to give some of the less-fertile rivers and streams kind of a jump start."
The writer lives in McMinnville, Oregon.