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Study: invasive prey extend feeding season for Columbia Basin walleye
Summary
Researchers told the FISH Committee that a year‑long Snake River study found walleye diets shift seasonally and invasive prey (Siberian prawns, American shad) expand forage availability, supporting the invasional‑meltdown hypothesis and indicating potential increased predation pressure when salmon are present.
Matt Polacek, Large Lakes Research Team Leader, presented findings from a year‑long study on the Snake River (Lower Monumental to Little Goose Dam) that combined diet (gastric lavage) and stable‑isotope analyses. “We caught a total of 5 25 walleye over the year, and 3 18 of those had stomach contents that were analyzed,” Polacek said as he summarized sample size and methods. He described seasonal prey shifts: Siberian prawns are available year‑round, shad dominate in summer–fall, resident fish appear seasonally, and salmon become the primary prey when they migrate through.
