Ecological Risk Screening Summary - Little Brown Mussel (Xenostrobus securis) - High Risk

Xenostrobus securis, little brown mussel, is a mollusk native to Australia and New Zealand. This species is typically found in estuarine environments, tolerating a broad range of substrates, temperatures, and salinities. However, it cannot survive in freshwater or seawater. X. securis is spread via ship ballast water and through accidental release in shellfish aquaculture. It can heavily alter pre-existing benthic communities and reducing populations of native mussels, barnacles, and cultured oysters. The History of Invasiveness for Xenostrobus securis is classified as High due to the ample information available about the introductions and negative impacts of this species. The climate matching analysis for the contiguous United States indicates establishment concern for this species, with high climate matches found along parts of each of the Gulf, Atlantic, and Pacific coasts. The climate match does not account for salinity tolerance, and therefore may not reflect actual establishment concern for inland areas. The Certainty of Assessment for this ERSS is classified as Low because of the salinity requirements of this species and the increased uncertainty around how widely it may be able to establish in the contiguous United States. The Overall Risk Assessment Category for Xenostrobus securis in the contiguous United States is High.

Species that are considered high risk have a well-documented history of invasiveness in at least one location globally, and a high or medium climate match to the contiguous United States.