Ecological Risk Screening Summary - Smooth Marron (Cherax cainii) - High Risk

Species that are considered high risk have a well-documented history of invasiveness in at least one location globally, and a high or medium climate match to the contiguous United States.

The Smooth Marron, Cherax cainii, is a large, freshwater crayfish species native to Southwestern Australia. This species was formerly considered Cherax tenuimanus until the two were determined two individual species in 2002. The history of invasiveness is classified as High. Cherax cainii has naturally expanded from its native range, and been purposely introduced outside of its native range in Southern Australia. The introductions of this species have led to established populations. In one area of introduction, negative impacts have been reported such as outcompeting native crayfish, leading to significant population declines. Cherax cainii is found in the aquarium trade in Japan and is also farmed at aquaculture facilities. Studies were conducted on the aquaculture potential of C. cainii in the southern United States in the late twentieth century, but mortality was high in both experiments and the climate was deemed unsuitable for C. cainii in aquaculture in the United States. Cherax cainii is listed as a prohibited species in Arizona, Florida, Nevada, Texas, and Utah, and may be regulated in Washington. The overall climate match category for the contiguous Unites States is Medium. Areas of high match were found along the West Coast. Medium to low match was found throughout the remaining contiguous United States. The certainty of assessment is Medium due to taxonomic uncertainty caused by distinguishing Cherax cainii and Cherax tenuimanus as two distinct species in 2002. The overall risk assessment is High.