THE TINY, lacy crustaceans look innocuous, but they are invaders, say scientists surveying nonnative aquatic animals and plants in the middle Columbia and lower Snake rivers.
The survey, conducted by Portland State and University of Washington scientists, documented 50 species introduced in the rivers, including three crustaceans not reported previously.
Funded by the U.S. Fish and Wildlife Service, the survey found fish, such as the common carp and eastern brook trout, the most frequently introduced species. The list also includes aquatic plants, mollusks, worms, and more crustaceans, all brought to Northwest waters since the 1880s.
Often nonnative animals and plants are introduced to waterways through commercial ship hulls and their ballast water. But this study, which was conducted farther up both rivers, discovered that these invaders were brought in through wildlife enhancement and intentional stocking of fisheries.
"Oregon has come a long way in addressing the aquatic invasive species issue in ballast water, but this study shows we have a lot more work to do," says Mark Sytsma, PSU director of the Center for Lakes and Reservoirs and main investigator on the project.
For the full report, visit www.clr.pdx.edu.
[photo: Asian clams]