Occurrence of the Ponto-Caspian mysid shrimp Hemimysis anomala (Crustacea, Mysida) in the St. Lawrence River

An invasive Ponto-Caspian shrimp, the bloody-red mysid Hemimysis anomala, is recorded for the first time in the St. Lawrence River near Montreal. The presence of gravid females and juveniles suggest an ongoing colonization of the river, likely driven by downstream dispersal of individuals from source populations in Lake Ontario. Two years after being discovered in Lake Michigan and Lake Ontario, H. anomala has now been recorded in all major waterbodies within the Great Lakes-St. Lawrence system, except for Lake Superior.