Observable impairments predict mortality of captured and released sockeye salmon at various temperatures.
Migrating adult sockeye salmon frequently encounter commercial and recreational fishing gear, from which they may be landed, escape or be intentionally released. In this experiment, migratory adult sockeye salmon were exposed to simulated capture-release in fresh water, including 3 min of exhaustive exercise and 60 s of air exposure at three ecologically relevant water temperatures (13, 16 and 19°C) to understand how thermal and capture-release stressors may interact to increase mortality risk. Water temperature and sex were the factors that best predicted 24 and 48 h survival, with females in the warmest temperature group experiencing the greatest mortality. Capture-release treatment including air exposure was associated with equilibrium loss and depressed ventilation rates at release; the probability of fish surviving for 24 h after simulated capture-release was >50% if the duration of equilibrium loss was <2 min or ventilation frequency was >1 breath s(-1). Higher haematocrit and plasma lactate as well as lower mean cell haemoglobin concentration and plasma sodium and chloride 30 min after simulated capture-release were also significant predictors of 24 h survival. Together, the results demonstrate that simple observations that are consistent with physiological disturbance can be used as predictors for post-release short-term survival for sockeye salmon. The markedly higher post-stressor mortality observed in females demonstrates that managers should consider sex-specific variation in response to different fisheries interactions, particularly in the face of climate change.
Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4.
Marika Kirstin
MK
Gale
Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4.
Scott G
SG
Hinch
Fish Ecology and Conservation Physiology Laboratory, Ottawa-Carleton Institute of Biology and Institute of Environmental Sciences, Carleton University, Ottawa, Ontario, Canada K1S 5B6.
Steven J
SJ
Cooke
Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4; Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, 1102 S. Goodwin Ave., Urbana, IL 61801, USA.
Michael R
MR
Donaldson
Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4; Fish Ecology and Conservation Physiology Laboratory, Ottawa-Carleton Institute of Biology and Institute of Environmental Sciences, Carleton University, Ottawa, Ontario, Canada K1S 5B6.
Erika J
EJ
Eliason
Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4; Anatomy, Physiology & Cell Biology, School of Veterinary Medicine, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
Ken M
KM
Jeffries
Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4; Fish Ecology and Conservation Physiology Laboratory, Ottawa-Carleton Institute of Biology and Institute of Environmental Sciences, Carleton University, Ottawa, Ontario, Canada K1S 5B6.
Eduardo G
EG
Martins
Cooperative Resource Management Institute, Fisheries and Oceans Canada, School of Resources and Environmental Management, Simon Fraser University, TASC 1 - Room #8405, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6.
David A
DA
Patterson
Fisheries; mortality; stress; temperature