A member of the expansive minnow family, the northern pikeminnow or Columbia River dace was officially renamed to “pikeminnow” in 1999 by the American Fisheries Society. Sometimes referred to as “squawfish”, they can live over 15 years old, grow to over 24 inches (over 60 cm) long, and weighing as much as 8 lbs. (~3.5 kilograms). Mature females can lay about 30,000 eggs each year. Pikeminnow are voracious predators in the Pacific Northwest of the U.S., with salmon smolts making up much of their diet.
Over the years, fisheries researchers have learned that anthropogenic structures (e.g., dams, reservoirs, bridges and overpasses) can create ideal predatory “hot spots” along migratory corridors and pathways for young salmon. Recently, scientists have learned that reservoirs created by hydropower dams on the Columbia River in this region create ideal habitat that give pikeminnow advantages over struggling salmon and steelhead populations.
A good example comes from the U.S. Fish & Wildlife Service and the Washington Department of Transportation. Working with a team of researchers, they set out with HTI acoustic tags to learn more about behavior, habitat use, fitness and survival of fishes at a major Seattle bridge referred to as the “520 Bridge”. Researchers monitored pikeminnow movement in fine-scale 2D, along with that of Chinook salmon smolts and smallmouth bass. Being able to track each species, they began to answer fitness and survival questions for the existing bridge, as well as gain many insights into how the future bridge might be designed and sited to minimize negative impacts on migrating salmon.
See how they did it and find out what they learned: