Angela D. Abel, Portland State University, (503) 725-8794
Amy Gaskill, U.S. Fish and Wildlife Service, (503) 231-6120
Scientists at Portland State University and the University of Washington have jointly completed the first targeted survey of nonnative aquatic plants and animals in the middle Columbia River (Bonneville Dam to Priest Rapids Dam) and the lower Snake River (upstream to the Washington-Idaho border).
The study, funded by the U.S. Fish and Wildlife Service, documented the introduction of 50 species since the 1880s. Fish such as the common carp and eastern brook trout represented the majority of introduced species, but the list also includes aquatic plants, crustaceans, mollusks and worms.
The survey discovered three new introduced species of small crustaceans not reported previously in the Columbia River basin. These animals include:
*The isopod Caecidotea laticaudatus;
* The amphipod Crangonyx floridanus (also present in the San Francisco Bay/Sacramento River system);
*And the harpacticoid copepod Harpacticella paradoxa (also present in Klamath River estuary, Calif., and the Samish River estuary, Wash.).
The Middle Columbia River Aquatic Nonindigenous Species Survey (MCRANS) included a review of scientific papers and publications as well as samples collected from numerous locations in the middle Columbia and lower Snake Rivers during 2006. This survey included eight reservoirs and the free-flowing Hanford Reach.
The MCRANS study follows an earlier survey of the lower Columbia River, extending the availability of baseline information that can help gauge future invasive species trends. While ballast water and vessel fouling from commercial shipping represent a key pathway in how species are introduced in the lower Columbia, MCRANS revealed that the most common vector for species introductions above Bonneville Dam was intentional stocking for fisheries and wildlife enhancement.
Although ballast water is typically not carried by vessels moving through the middle Columbia River and lower Snake Rivers, tug and barge traffic may still represent a source of invasive species spread within the basin. Recreational boating was associated with only a small number of nonnative species found in this region of the Columbia and Snake Rivers, but still represents a major threat of introducing species like aquatic weeds and zebra mussels. The MCRANS report recommended additional monitoring and sampling to detect new invasions and to document invasion rate, impacts and efficacy of management efforts.
"The Columbia River system is part of the lifeblood of the Pacific Northwest, and this survey represents an important step in measuring the extent that nonnative species have changed that system" said Ren Lohoefener, U.S. Fish and Wildlife Pacific region director, Portland. "But we know that not all aquatic nonnative species cause problems, and so additional information is still needed to determine how the presence of these species translates into economic and ecological impacts."
The report points out that nine major dams were constructed on the middle Columbia River and the lower Snake between 1938 and 1975. Disturbance to the system may have facilitated invasion by the Aquatic Nonindigenous Species and increased the rate of invasion. The series of reservoirs created by the dams also may have served as "stepping stones" for upriver movement of nonnative species already in the lower Columbia River and estuary. For example, the survey found that a small planktonic copepod native to Asia that was first seen in the Columbia River estuary in 2002 has managed to move upstream and is now very abundant in the four lowest reservoirs. The bulk of species identifications in the middle Columbia, however, were published after the completion of the dams, which makes estimation of historic rates of introduction impossible.
"This survey sets a baseline to evaluate how effective we are in reducing the rate of aquatic bioinvasions by shipping-related pathways and others as well," said Mark Sytsma, PSU director of the Center for Lakes and Reservoirs and co-principal investigator on the project. "Oregon has come a long way in addressing the aquatic invasive species issue in ballast water with the support of the ports and shipping industry, but this study shows we have a lot more work to do."
SOURCES: Mark Sytsma, PSU Center for Lakes and Reservoirs (503-725-3833)
Robyn Draheim, PSU Center for Lakes and Reservoirs (503-725-4994)
Jeffery Cordell, University of Washington (206-543-7532)
Paul Heimowitz, U.S. Fish and Wildlife Service (503-736-4722)
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