SALMON NEED SALMON, SCIENTISTS SAY IN NEW STUDY 

According to a new scientific paper published by the Washington Department of Fish and Wildlife, coho salmon grew twice as fast in streams enriched by salmon carcasses and were nearly 50 percent bigger than coho raised without the extra nutrients. Bigger juveniles means better survival in both fresh water and marine environments. In one study of fish from a tributary of the Snoqualmie River in western Washington, juvenile coho salmon, cutthroat trout and steelhead obtained up to 40 percent of the carbon and nitrogen in their muscle tissue from the carcasses of adult coho. 

But salmon are not the only beneficiaries of nutrients from the salmon carcasses. The study said that 137 other wildlife species make use of them as well. These include animals such as the white-tailed deer (rare relationship through eating salmon carcasses) and both black and grizzly bears that have a strong, consistent relationship to salmon. Many species of birds also benefit from salmon. 

The study, titled Pacific Salmon and Wildlife, Ecological Contexts, Relationships, and Implications for Management, notes the numerous pathways of marine nutrients and how they are utilized by the ecosystem. 

For example, riparian plants contain high levels of marine nitrogen and carbon derived from salmon carcasses. These riparian plants, in turn, provide salmon with benefits that include shading the stream, while also providing more than over 90 percent of the organic nutrients that support other aquatic life, as well as large wood that helps retain nutrients and sediments important for both productivity and spawning. 

"Accumulating evidence suggests that spawning salmon populations are an important link to the adjacent riparian and terrestrial communities," the authors say, "and indeed, fortifies the role of salmon as a keystone species, wherein the integrity and persistence of the entire community is contingent upon the population's actions and abundance." 

But as the salmon runs decline, the import of nutrients declines, which leads to a drop in stream productivity--another factor, the authors say, that is contributing to declining salmon runs. "In general, escapement trends (adult salmon that escape the fishery to spawn) have been downward since 1970 for all populations...the number of salmon now returning to Washington and Oregon rivers is only 3.3 percent of the historical biomass...and this nutrient deficit may be one indication of ecosystem failure that has contributed to the downward spiral of salmonid abundance and diversity in general, further diminishing the possibility of salmon population recovery to self-sustaining levels." 

But states have the regulatory authority to determine how many salmon are harvested and how many are allowed to spawn. According to the authors, of the 113 wild salmon stocks in Washington that have established spawning escapement goals, "only 46 (41 percent) met these goals as of the early 1990s." In Oregon, they say, "no determination of the spawning escapement needs has been made for wild steelhead, chum salmon,...or searun cutthroat trout." 

In Oregon, the state's Fish and Wildlife Department has set a spawner escapement goal of 42 fish per mile for coho salmon. Even though this goal has yet to be reached, the 42 fish per mile fell well short of the 160 fish per mile needed to return adequate nutrients from salmon carcasses to coho streams. 

"Managing at the MSY (Maximum Sustained Yield) level may have the effect of substantially reducing the delivery of marine derived nutrients to freshwater habitats," the authors say. They recommend "a shift from MSY to more ecologically based stock management objectives." 

In addition, "widespread use of salmon hatcheries has also significantly reduced the amount of salmon carcass nutrients available for aquatic food webs," the study says. Hatcheries function as huge nutrient traps because returning fish are removed from the stream. Dams at hatcheries have been used to keep fish diseases from spreading upstream, but the practice has also kept nutrients out. However, new emphasis on nutrient enrichment from carcasses has led some states to use volunteers to distribute hatchery salmon carcasses into streams. The authors say action is needed now; the region needs "an uncompromising and all-encompassing plan to protect and recover wild salmon populations before the system is unrecoverable."-Bill Bakke 

To order a copy of this study please contact David H. Johnson, Washington Department of Fish and Wildlife, Habitat Program, 600 Capitol Way N., Olympia, WA 98501-1091. His email is: johnsdhj@dfw.wa.gov.

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