Expansion of the White River Crayfish (Procambarus acutus) in Ontario, Canada

Abstract The invasive White River crayfish, Procambarus acutus (Girard, 1852), has recently been reported from several regions of central Ontario, Canada through the online platform, iNaturalist as well as the Invading Species Awareness Program. Between September 2022 and September 2025, we conducted surveys to confirm these reports. Our results show that P. acutus is now established and reproducing in the Severn Sound region where we collected a female with eggs and reports of females carrying young and freeliving young of the year have been posted on iNaturalist since. In 2024, a report of suspected P. acutus in Oakbank Pond in Thornhill, Ontario was confirmed by subsequent surveillances resulting in multiple captures from burrows in ditches near the pond, including a female carrying young. Our observations indicate the species is established and surviving in and around the pond and poses a risk of invasion into the headwaters of the Don River, one of the major tributaries to Lake Ontario. Our study confirms the presence and establishment of P. acutus in the Port Severn region, as well as Oakbank Pond in Thornhill, and expands the distribution of this species in Ontario and, as a result, Canada.