Ecological Risk Screening Summary - Wakasagi (Hypomesus nipponensis) - 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.

The Wakasagi (Hypomesus nipponensis) is a freshwater and brackish fish native to Japan, as well as the continental rivers of eastern Russia and the Korean peninsula. H. nipponensis can migrate from freshwater to brackish but also has resident populations in freshwater lakes. Spawning occurs in fresh or low brackish waters. In its native range, the Wakasagi supports both commercial and recreational fisheries. In the early 1960s, H. nipponensis was intentionally introduced and the species has now established populations across California. This species has also been introduced and established in China related to aquaculture activities. There are documented impacts on native species in both California and China. Impacts include changes in fish populations, trophic structures, and hybridization with the federally listed endangered delta smelt (Hypomesus transpacificus) in California. The history of invasiveness is High. No species-specific regulations were found for this fish and no information to quantify trade was found. The climate matching analysis for the contiguous United States indicates establishment concern. The majority of the contiguous United States had a medium climate match with area of high match found in the Northern Pacific Coast, California, Great Basin, and Western Mountain regions. The certainty of assessment for this species is High. The Overall Risk Assessment Category is High.