Tracing Food-Web Effects of Spawning Salmon
Scientist: Laura Livingston, School of the Environment (Pullman)
Reporter: Carly Ray, Murrow College of Communication (Pullman)
The Pacific Northwest is re-evaluating habitat restoration for Pacific salmon. The question at hand: Are the billions of tax dollars and efforts being applied towards restoring streams and dams actually realizing restored salmon populations?
Multiple teams of scientists across the Pacific Northwest are dedicating their careers to finding out. Washington State University is at the forefront of this movement that is attracting attention at a national level.
Salmon have been returning to Pacific Northwest streams since at least ten thousand years ago when the last large glaciers retreated from the region. Ecologists have wondered how these spectacular and enduring migrants affect stream ecosystems.
Laura Livingston, a WSU Environmental Science graduate student, is part of this study and is focusing her research in the Methow River basin of Washington State. The Methow is one of the northernmost rivers salmon can turn into as they swim up the Columbia River and is the home of many salmon restoration projects.
One of these projects is conducted on the Methow at Hancock Springs where Yakama Nation scientists have been studying how the food web responds when artificial salmon carcass material is added to mimic dying salmon and increases the amount of food available in streams. Livingston has partnered with them to measure how natural salmon carcasses may benefit stream invertebrates. These invertebrates, in turn, are an important part of the stream food web, providing nutrition for fish, including juvenile salmon.
Salmon are the true icons of the Pacific Northwest. It seems most citizens of the Northwest—whether fishermen, Native American tribesmen, or simply anyone who enjoys eating salmon—are stakeholders in the interests of Pacific salmon.
Salmon populations sharply declined in the years after the construction of the Grand Coulee Dam in 1942. Since then, the salmon runs that once filled rivers are only a shadow of what they once were. In fact, historical estimates of salmon returning to Pacific Northwest streams before 1942 range from thirty-three to fifty-eight million fish each year. Today, however, annual returning salmon counts hover around two million fish. Conservation efforts seek to maintain salmon populations and their ecological impacts throughout the region by improving fish passage across dams and restoring habitat.
Livingston’s work evaluates the downstream effects of these efforts. By visiting Methow rivers during the fall spawning season, she analyzes invertebrates living near salmon carcasses. The spawning and “die-off” of salmon correspond to the seasonal change from summer to fall. And consequently both of these events affect the invertebrates in the spawning rivers.
Other researchers have found that the carcasses benefit invertebrates and the stream food web by bringing nutrients from the sea back to the streams.
Livingston’s investigation explores whether invertebrates gather to feed on salmon carcasses, creating a hotspot of prey in the stream. Her research contributes to a larger body of research focused on determining how salmon impact streams and how fisheries managers can influence that impact in a time of shrinking salmon populations.
Learning about invertebrate reliance on natural salmon carcasses provides a useful comparison for fisheries managers such as the Yakama Nation scientists.
Just as declining salmon populations have ripple effects throughout a stream ecosystem, conserving salmon populations also may also lead to benefits that spread to other species. When it comes to Pacific Northwest ecosystems, everything is interconnected.
Livingston and the rest of the team at WSU are eager to play their part in a large project that may one day help scientists efficiently rehabilitate streams to restore salmon populations in not just Hancock Springs, but the entire Pacific Northwest region.