Hemimysis anomala G.O. Sars, 1907 expands its invasive range to Northern Ireland

The invasive crustacean Hemimysis anomala was first discovered in the Republic of Ireland in April 2008. By 2009 it had extended its range to lakes throughout the navigated River Shannon waterway, occasionally occurring in large swarms in shallow waters and in lower densities at deep sites. In this study, a standardised stratified fish survey of Upper Lough Erne in 2013 found H. anomala in the stomach contents of four perch (Perca fluviatilis). These fish were captured at sites located at the northern and southern extremes of the lake, suggesting that invasive H. anomala are distributed throughout this waterbody. This catchment is directly linked to the River Shannon through the Shannon– Erne canal and our data indicates that, as previously predicted, the distribution of H. anomala now includes Northern Irish freshwaters.