Ecological Risk Screening Summary - European Fingernail Clam (Sphaerium corneum) - 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.

Sphaerium corneum, European Fingernail Clam, is a mollusk that is native to Eurasia. These clams mature in 3 months at around 4 mm. S. corneum are found in freshwater lakes, pools, streams, and slow-moving rivers; however, they prefer more eutrophic, lentic bodies of water. These bottom filter feeders can be found nestled in the sediment or even attached to the aquatic vegetation up to 40 m deep. S. corneum was most likely introduced through the release of solid ballast, a method used prior to the 1900s. S. corneum has also been observed dispersing on a smaller scale by attaching to other species (e.g., diving beetles and pond-dwelling amphibians). The History of Invasiveness for Sphaerium corneum is classified as Data Deficient due to a lack of data regarding impacts (or lack of impacts) of introduced populations. The climate matching analysis for the contiguous United States indicates establishment concern for this species. The highest climate matches were found in the Upper Midwest and Northeast. Much of the rest of the contiguous United States had a medium match. The Certainty of Assessment is classified as Low due to a lack of information regarding impacts. The Overall Risk Assessment Category for Sphaerium corneum in the contiguous United States is Uncertain.