The Life History of the Rusty Crayfish (Faxonius rusticus) in a Small Southern Ontario Stream

An intensive, long-term study of the life history of O. rusticus was conducted in Fleetwood Creek, a small stream in Southern Ontario, Canada. The reproductive biology as well as molting cycle were investigated and the larval development and morphology was documented in detail for the first time in this important invasive species. Despite recent climate change effects, such as higher maximum temperatures as well as significant short term temperature fluctuations, the overall life cycle does not appear significantly different from previous studies conducted in the 1980s and 1990s but the crayfish activity appeared to be affected by temperature fluctuations associated with climate change. Mating and spawning occurred in the first week of April. The onset of mating and spawning occurred at temperatures of 9-10°C which was somewhat higher than previously reported for this species in this region of Ontario. Abdominal eggs were carried for approximately 7-weeks and larval stages remain attached to their mothers between 12 and 15 days. Free-living young were first observed in early June. Maturity is attained within the first summer, at 19-20 mm carapace length, in at least 30% of the young-of-the-year and most individuals of both sexes are mature at 25 mm carapace length. Monitoring was conducted weekly and daily during molting and spawning periods in spring 2021 and 2022, which makes this study unique with respect to most other life history field studies.