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Nutritional status of salmon streams
Nutritional status of salmon streams
Problem Statement
Declines in salmon abundance over the last century have resulted in decreased
deposition of marine-derived nutrients from salmon carcasses in streams.
The effect of this nutrient subsidy reduction on freshwater habitat productivity
in the Columbia River watershed must be evaluated.
Critical Factors
- Impacts on freshwater habitat productivity due to the loss of nutrient
subsidies from salmon carcasses pose a significant restraint on recovery
of threatened and endangered Pacific salmon.
- The Columbia River Basin streams have long been starved for the essential
nutrients from salmon carcasses and this nutrient starvation has impaired
salmonid productivity.
- It is necessary to determine minimum nutrient levels needed to maintain
optimum salmon production.
Status of Research
Preliminary studies are now underway to evaluate the nutritional
status of selected tributaries in the Columbia River Basin using stable
isotope analysis. The use of stable isotope analysis has enabled direct
quantitation of marine-derived nutrient enrichment of streams by salmon
carcasses. Researchers in the Northwest Fisheries Science Center's (NWFSC)
Watershed Program have shown that the addition of hatchery-spawned carcasses
to Washington coastal streams improved the condition and caused increased
density of juvenile coho salmon and steelhead. In addition, juvenile coho
at the sites to which carcasses were added grew at more than twice the rate
of fish in a nearby stream containing few carcasses. This result is noteworthy
because increases in body size of juvenile salmonids can significantly increase
their survival. Stable isotope analysis of fish tissues confirmed that
marine-derived nutrients from salmon carcasses were responsible for the
increased growth observed in these juvenile salmonids.
Future Considerations
Decaying chinook salmon
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While recent work has focused on the impact of salmon carcasses on coastal
stream communities, the effect of salmon carcasses on nutrient-deficient
interior streams of the Columbia River Basin must also be evaluated.
By doing stable isotope analysis on samples (e.g., fish, vegetation,
invertebrates) collected from sites with a wide range in spawning salmon
densities, it is possible to determine whether saturation of marine-derived
nitrogen is occurring and, if so, at what densities. This information will be
essential in establishing spawning escapement levels (i.e., fish remaining after harvest)
for upriver chinook to assure optimum salmon production.
Key Players
Environmental Conservation (EC) Division, NWFSC
Bonneville Power Administration
Columbia Basin Fish & Wildlife Authority
Columbia River Inter-Tribal Fish Commission
Fisheries agencies in Washington, Oregon, and Idaho
Northwest Power Planning Council
Oregon State University
Pacific Fishery Management Council
Snake River Recovery Team
University of British Columbia
University of Washington
U.S. Army Corps of Engineers
U.S. Environmental Protection Agency
U.S. Forest Service U.S. Fish & Wildlife Service
U.S. Geological Survey
Washington Tribes
Washington Department of Natural Resources
Weyerhauser Company
Contact: Dr. Tracy Collier, Director, EC Division (206/860-3312)
NWFSC Issue Paper EC 6508 (HQ ID 314)
Issue Papers Home
last modified 2002-07-29
Web site owner: Northwest Fisheries Science Center
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