Not so long ago, when great runs of wild salmon still ruled the Northwest, fish carcasses littered the banks of streams each spawning season. Scientists have long suspected that these rotting salmon helped fuel the food chain. But they didn't know to what extent.
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.
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
"We thought we would
see a sign, but we had no idea it would be so large," says
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
"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
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
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,