Ecological Risk Screening Summary - Shimofuri Goby (Tridentiger bifasciatus) - Uncertain Risk

Species that are considered uncertain risk need a more in-depth assessment beyond the Risk Summary to better define the species’ risk to U.S. environments.

Tridentiger bifasciatus, Shimofuri Goby, is a fish species native to China, Taiwan, South Korea, Japan and Russia. First introduced in 1985 via a ship’s ballast hull, the species is now firmly established and abundant in the vicinity of San Francisco, California. It has spread throughout the State via the California State Water Project, reaching several lakes in southern California. The species is also established outside its native range in China. In California, scientists speculate it could negatively affect the federally endangered tidewater goby Eucyclogobius newberryi if the two come in contact given their shared habitat and dietary preferences. The major proposed mechanism of impact on native species is competition for food resources. History of invasiveness is classified as “none documented” because T. bifasciatus is established beyond its native range, but there is not yet any clear and convincing evidence of purported negative impacts. Climate match with the contiguous United States was high. Certainty of assessment is low due to equivocal information on impacts. Until more definitive studies are available on the impacts of T. bifasciatus, the overall risk assessment for the species is uncertain.