Establishing river by river, ecologically meaningful temperature triggers for behavioural thermoregulation in juvenile Atlantic salmon
It is well understood that Atlantic salmon will seek thermal refuge once certain temperature thresholds are exceeded, and these thresholds differ with age – this behaviour is termed ‘thermoregulation’. However, the temperature that induces behavioural thermoregulation is not homogeneous across the range of Atlantic salmon. Work by Corey et al., (2020) found the temperatures that trigger behavioural thermoregulation varied in two unique geographic areas: the Ouelle River (QC) and the Miramichi River (NB). Further, recent work by O’Sullivan et al., (in review) found the temperatures that trigger behavioural thermoregulation in juvenile Atlantic salmon at a site on the Miramichi River can vary throughout a summer – see Figure 1. As our understanding of the mechanisms that underlie these processes has grown, it is now evident that (a) we cannot apply a spatially homogenous threshold for behavioural thermoregulation across the range of Atlantic salmon, and (b) even if different thresholds are defined for individual rivers, these are not static; rather they will flux throughout a summer. This new knowledge challenges our current management paradigm, where the same temperature thresholds are used to manage Atlantic salmon throughout eastern Canadian rivers, e.g., (DFO, 2012).
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