First record of Orconectes rusticus (Girard, 1852) (Decapoda, Cambaridae) west of the Great Continental Divide in North America

Abstract

Orconectes rusticus (Girard, 1852), known as the rusty crayfish, have spread over the last 50 years from their historical range in the Ohio River drainage, United States, to waters throughout much of 18 additional eastern and central states, provinces of Ontario and Qu?bec in Canada, and the Laurentian Great Lakes (Hobbs et al., 1989; Olden et al., 2006; Taylor et al., 2007). O. rusticus are omni vores and aggressive, resulting in numerous ecological and evolutionary impacts manifested across entire food webs. The invasion of this species has been associ ated with negative effects on aquatic plants, invertebrates, snails, and fishes (e.g., Olsen et al., 1991; Lodge et al., 1994; McCarthy et al., 2006), in addition to dis placing and hybridizing with native crayfish (e.g., Perry et al., 2001). The most westward reported occurrences of O. rusticus are the North Platte River near Dou glas, Wyoming (where the population is believed to have been successfully eradi cated) and Conchas Lake in north-east New Mexico (Bouchard, 1977). Preventing the westward spread of aquatic nuisance species from eastern North America is a primary goal of the 100th Meridian Initiative (http://www.100thmeridian.org). Here we are the first to document the presence of O. rusticus west of the Continental Divide in North America, separating watersheds that drain into the Pacific Ocean from those river systems that drain into the Atlantic Ocean. On 19 July 2005, a field survey conducted by the Xerces Society for Invertebrate Conservation and the Confederated Tribes of Warm Springs Reservation of Oregon revealed the occurrence of a non-native Orconectes sp. crayfish in the upper