Science Advisory Report  2012/019

Temperature threshold to define management strategies for Atlantic salmon (Salmo salar) fisheries under environmentally stressful conditions

Summary

• Temperature tolerance in Atlantic salmon is size-specific with adult salmon less tolerant of high temperatures than juveniles.
• There is limited information on optimal temperatures and critical temperatures that define the aerobic scope for adult Atlantic salmon and inferences are made based on evidence from juvenile life stages of Atlantic salmon and other species.
• The temperature thresholds proposed are based on bioenergetic considerations. A daily minimum water temperature (T_min) of 20ºC is proposed to be most important for physiological recovery and survival of Atlantic salmon.
• The proposed closure trigger is if the minimum water temperature (T_min) during each of two consecutive days equals or exceeds 20°C.
• The proposed opening trigger is if the minimum water temperature (T_min) during each of two consecutive days is less than 20°C.
• Mean water temperatures show spatial structure within the Miramichi River and the Restigouche River based on main stem or tributary sites and distance from the estuary.
• The management performance of the proposed closing and opening triggers can be assessed by retrospective evaluation using criteria such as the number of closures and the duration of the closures.
• The number of salmon vulnerable to mortality from angling activities during warm water conditions is not known. In river mortalities of adult Atlantic salmon are not systematically documented in either the Miramichi or Restigouche rivers and angling statistics at a temporal scale sufficient for assessing the potential impacts of angling during warm water periods are not available.
• Other human activities can displace fish and contribute to stress on Atlantic salmon during warm water events including wading in streams, swimming in pools, boat traffic, as well as scientific activities.

This Science Advisory Report is from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, regional peer review meeting of March 15, 2012 on the development of Environmental Thresholds to Define Management Strategies for Atlantic Salmon Fisheries under Environmentally Stressful Conditions. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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