Open Collections

Hnytka, Sarah

University of British Columbia

Stream temperature is a key driver of physiological function in ectothermic fish, and fish have clear upper and lower limits of thermal habitat, bounding a range of optimal conditions. Predicted stream temperature increases from climate change are a major threat to Athabasca Rainbow Trout (Oncorhynchus mykiss; ARBT) which are listed as Endangered under Schedule 1 of Canada’s Species at Risk Act. Knowledge gaps concerning temperature preferences, thermal limits, and habitat suitability need to be addressed to effectively manage and recover this endemic ecotype. In this study, ARBT were collected from July – August in 2021 and 2022 from three streams in the McLeod River watershed, Alberta, Canada, representing a gradient of thermal regimes ranging from cold to warm. Fish were tested for four physiological metrics: agitation temperature (Tag), critical thermal maxima (CTmax), avoidance temperature (Tavoid) and preferred temperature (Tpref) using a portable streamside laboratory. Both Tag and Tavoid metrics are indicators of behavioural avoidance responses, whereas Tpref represents the optimal temperature zone for metabolism and growth. Finally, CTmax can be interpreted as a population’s upper thermal limit where long term survival is reduced. These metrics can influence habitat selection and distributional limits, and will likely be increasingly important indices of thermal performance and stress under climate change. Determining whether ARBT populations are able to cope with varying stream temperatures by plastically shifting their thermal tolerance is a key consideration for understanding their adaptive potential. Results from stream-side experiments provide strong evidence that the majority of thermal responses (CTmax, Tavoid and Tpref) are plastic allowing for a greater level of physiological resilience. However, given that increasing stream temperatures may lead to subpar thermal habitat, ARBT will likely be forced to adapt or find new habitat in certain streams. This work is intended to support the prioritization of recovery locations within the Athabasca Rainbow Trout’s distribution.

Text

2023-12-18

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86969

Oceans and Fisheries

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/