Article on Salmon Carcasses
February 8, 2000
Salmon decline hurts many other species
By JEFF BARNARD
Associated Press Writer
GRANTS PASS, Ore. -- A growing body of scientific evidence is showing that
salmon are more than just a majestic sport fish, a tasty entree, an economic resource or a cultural icon.
From Alaska to California, they serve as a huge natural recycler,
responsible for transporting organic material they eat in the oceans and
store in their bodies before swimming to the headwaters of watersheds,
leaving their rotting carcasses to feed insects, bears, plants, trees and
particularly baby salmon.
A recent study published in the journal Fisheries figures that as little
as 5 percent of the historical biomass of salmon are returning to their
native watersheds, creating a dramatic shortage of nutrients derived from
The recycling role is so important that restoration of wild salmon in the
Pacific Northwest "is hinging on recognition of this issue," said Jeff
Cederholm, a fisheries scientist with the Washington Department of
Historically, salmon management has been based on allowing the maximum
catch in the ocean and rivers while allowing just enough fish to return
to their native streams to spawn a new generation.
"We have essentially starved our freshwater systems," said Bob Bilby, a
fisheries scientist with the National Marine Fisheries Service in
Based on historical cannery records and published accounts, researchers
estimated the annual biomass of salmon returning to rivers before the
arrival of settlers in Washington, Oregon, Idaho and California.
They found that salmon runs totaling between 352 million pounds and 497
million pounds had declined to between 26 million pounds to 30 million
"This means that just 5 percent to 7 percent of the marine-derived
nitrogen and marine-derived phosphorous once delivered annually to the
rivers of the Pacific Northwest is currently reaching those streams," the
researchers say in their study.
"This nutrient deficit may be one indication of ecosystem failure," they
Jim Lichatowich, an independent fish biologist, Ted Gresh, a graduate
student in planning and public policy at University of Oregon, and Peter
Schoonmaker, executive director of the Institute of the Northwest
published their findings in the latest issue of Fisheries, the journal of
the American Fisheries Society.
"This is sort of like the erosion of genetic diversity," Lichatowich said
in an interview. "It is something you don't see, but accumulatively it
probably could have a big impact."
The key to this research has been equipment that can identify individual
isotopes of chemicals such as nitrogen, phosphorous and carbon, and track
them to their source. Using it, scientists have analyzed leaves, plants,
young fish and even grizzly bear bones. All showed high levels of
nutrients coming from the ocean.
On Washington's Olympic Peninsula, Cederholm observed 22 different
animals feeding on salmon carcasses.
"We have been finding marine carbon and nitrogen in leaf matter of trees
growing along river corridors," Cederholm said. "The only way for it to
get there is through salmon swimming up streams, spawning in rivers."
The trees in turn drop their leaves, branches, and eventually their
trunks into the river, where they serve as hiding and resting places for the
fish, and decompose to feed insects, which in turn are eaten by salmon.
"They are a keystone species," Cedarholm said of salmon. "All the other
wildlife or plant communities have, in some way, some dependency."
Working on the Snoqualmie River in Washington, Bilby found that as much
as 40 percent of the nitrogen in the bodies of young coho salmon and 60
percent of the nitrogen in young steelhead came from marine sources.
When they dumped salmon carcasses on streams running into Willapa Bay,
they found higher densities of young fish around the carcasses. The young
fish were feeding on the carcasses and eggs laid in the river.
The extra food meant juvenile fish grew bigger before migrating to the
ocean. Bigger fish survive better, so more fish come back to the river.
And so on.
It appears that salmon evolved this as a survival strategy because the
streams in the Northwest were generally low in nutrients. So they brought
their own lunch.
"If you don't have the subsidy provided by salmon, those systems
gradually decline," Bilby said. "You'll still have aquatic life occurring in those
streams, but there won't be much of it."
The Oregon Plan for restoring dwindling salmon populations recognized
this research, and for the past two years volunteers have been tossing salmon
carcasses from five hatcheries along coho rivers on the northern Oregon
Coast. Washington has a similar program.
But there is a long way to go, the authors of the Fisheries article
Research has indicated that between 93 and 155 carcasses per kilometer
are needed to provide the maximum ecological benefit on coho streams. While
Oregon's goal for coastal coho streams is 26 fish per kilometer, only two
to seven fish per kilometer were found in 1997.
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