Critical thermal refugia for Atlantic salmon and brook trout populations of eastern Canadian rivers

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This project involves 8 university researchers with a range of biological and hydrological expertises. It aims to study the physical controls and biological significance for salmonids of localized, cool water refugia sites along rivers in southern Quebec and New Brunswick. Under a 21st century regime of warming summers, such thermal refugia may become key, limiting habitats for the survival of our dominant cold water sport fish, salmon and brook trout, at the southern limits of their population range. Cool thermal refugia are both heterogeneous and visually inconspicuous: they range widely in dimensions, spatial distribution and physical controls: some are associated with groundwater upwellings along river beds, others with the mouths of particular tributaries and some, with small hyporheic seeps. The typical separation between these cryptic habitats along salmon or trout rivers systems is poorly known as is the ability of salmonids to detect and migrate significant distances to such sites, or fish mortality rates as a function of distances and temperature patterns. Moreover, under likely scenarios of future temperature, rainfall and snow cover conditions for the later 21st century, the relative dimensions and value as thermal refugia of major types of in-stream groundwater upwellings is also unclear. This project will apply thermal IR detection combined with fish ecology field surveys to study the spatial distribution and support capacity of these habitats. Generic hydrogeological models will explore a range of in-stream groundwater upwelling settings in context of regional climate scenarios. Our industrial partner Hydro-Quebec needs our state of the art tools and models to monitor and predict effects of river flow modifications (and deep reservoir releases) on fish habitats (including thermal refugia) on the river ecosystems they impact. Broad environmental benefits for Canada can be expected in terms of adaptations to climate change of Boreal river ecosystem management and optimisation of future fish conservation investments, by clarifying to what extent future thermal regimes can limit the productivity or the survival of cold water species in individual rivers, as a function of its particular refugia spatial distribution.