Seasonal Variation in Critical Thermal Maximum of Redside Dace at the Northern Edge of Its Range

Session: Imperiled Species in the Great Lakes Basin: Identifying Threats and Restoring Populations (1)

Alexandra Leclair, University of Toronto Scarborough, [email protected]
Andrew Drake, Fisheries and Oceans Canada, [email protected]
Nicholas Mandrak, Biological Sciences, University of Toronto Scarborough, [email protected]

Abstract

Understanding the thermal performance of fishes is necessary to identify optimal thermal habitat, which can provide insight into how species productivity may shift under climate change. Using an experimental thermal chamber, we investigated seasonal variation in the Critical Thermal Maximum (CTmax) of wild-caught Redside Dace (n = 138) in Two Tree River, Ontario. Streamside CTmax trials were used to identify the maximum temperature at which Redside Dace maintain equilibrium, providing a powerful tool for understanding how thermal stress affects individual performance. By conducting monthly streamside trials June-October 2018, we assessed whether CTmax varied based on acclimation temperature, defined as the ambient temperature of the stream, and body size. Mean CTmax varied between 27.59°C and 33.63°C, based on minimum and maximum acclimation temperatures of  3.59°C and 24.39°C, respectively. Based on generalized linear models, preliminary results indicated a positive, linear relationship between acclimation temperature and CTmax. Significant differences were observed for both monthly mean ambient stream temperatures and CTmax in most cases, without a significant effect of body size. Results provide insight into the thermal performance of Redside Dace, which to-date has been difficult to assess due to the species rarity and lack of suitable streamside protocols.