First records of non-indigenous cyclopoid copepod Thermocyclops crassus (Fischer, 1853) in Eastern Canada.

We report the first records for the Eurasian zooplankton species Thermocyclops crassus (Fischer, 1853) (Copepoda, Cyclopoida) from two freshwater sites in eastern Canada collected between 2020 and 2022. Thermocyclops crassus were found at high densities (between 8 × 103 and 2 × 105 adults/m3) in Lake St. Pierre on the St. Lawrence River, Québec, but at very low densities (between 0.3 and 0.7 adults/m3) in Wentzell's Lake on the LaHave River system, Nova Scotia. We discuss possible introduction pathways for both sites as well as the need for enhanced biosurveillance and increased public education in eastern Canada. [ABSTRACT FROM AUTHOR]