Widespread Distribution of the Non-Native Northern Crayfish (Orconectes virilis) in the Columbia River Basin

We report here the first records of the non-native northern crayfish (Orconectes virilis) in the Columbia River basin within Washington State. Confirmed occurrences include the reservoirs Lake Rufus Woods and Lake Roosevelt on the Columbia River, North Twin Lake in the upper Columbia River basin, Lake Patterson in the Methow, River basin, Wapato Lake in the Lake Chelan basin, and Moses Lake in central Washington. Uncertainty remains as to the source, extent of current distribution, and potential impacts of these O. virilis populations. Release of live bait by anglers is a common pathway for crayfish introductions, although stocking for harvest or aquaculture and releases of pets or laboratory animals is equally likely for the introduction of O. virilis to the region. Evaluating potential impacts of O. virilis on native crayfish, fish, and other species in the Columbia River basin will require additional study. These newly discovered O. virilis populations are likely to naturally disperse further through the Columbia River, its tributaries, and the irrigation infrastructure of central Washington's Columbia Basin Project.