Ecological Risk Screening Summary - Asian Tapeworm (Schyzocotyle acheilognathi) - High Risk

Species that are considered high risk have a well-documented history of invasiveness in at least one location globally and are of establishment concern for the contiguous United States based on a climate matching analysis.

Schyzocotyle acheilognathi, the Asian tapeworm, is a fish parasite that is native to eastern Asia. Two of its common host species are the Common Carp (Cyprinus carpio) and Grass Carp (Ctenopharyngodon idella), both of which have been introduced globally for commercial purposes, which has contributed greatly to its spread. S. acheilognathi is extremely host-nonspecific and has been documented in hundreds of other fish species, especially cyprinids. High parasite load of this species is associated with mortality of small fishes in aquaculture settings. In native North American fish species, infection with S. acheilognathi has been associated with reduced growth and, particularly under high parasite load, increased mortality. The History of Invasiveness for Schyzocotyle acheilognathi is classified as High due to these negative impacts, as well as its wide introduction and establishment in host fishes outside of its native range. The climate matching analysis for the contiguous United States indicates establishment concern for this species. The climate match was high across most of the contiguous United States. The Certainty of Assessment for this ERSS is classified as High due to the substantial scientific evidence documenting nonnative establishment and negative impacts of S. acheilognathi. The Overall Risk Assessment Category for Schyzocotyle acheilognathi in the contiguous United States is High.