Ecological Risk Screening Summary - Dreissena caspia (a mussel, no common name) - 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.

Dreissena caspia was a mussel native to the Caspian Sea. It has not been collected or observed since the 1940’s. It is presumed to be extinct due to competition by the invasive mytilid Mytilaster lineatus, which was introduced in the Caspian Sea from the Black Sea. Most of the data regarding this species comes from the fossil record. This species has not been reported outside of its native range. History of invasiveness is No Known Nonnative Population. The climate match for the contiguous United States was high. Much of the central and western United States had a medium to high match. The climate match does not account for salinity tolerance. Species establishment will require both a suitable climate and the availability of aquatic habitat with appropriate salinity. The certainty of assessment is low due to the limited information about the species range and salinity requirements. The overall risk assessment category for D. caspia is Uncertain.