Disentangling the roles of air exposure, gill net injury, and facilitated recovery on the postcapture and release mortality and behavior of adult migratory sockeye salmon (Oncorhynchus nerka) in freshwater.
We sought to improve the understanding of delayed mortality in migrating sockeye salmon (Oncorhynchus nerka) captured and released in freshwater fisheries. Using biotelemetry, blood physiology, and reflex assessments, we evaluated the relative roles of gill net injury and air exposure and investigated whether using a recovery box improved survival. Fish (n=238), captured by beach seine, were allocated to four treatment groups: captured only, air exposed, injured, and injured and air exposed. Only half of the fish in each group were provided with a 15-min facilitated recovery. After treatment, fish were radio-tagged and released to resume their migration. Blood status was assessed in 36 additional untagged fish sampled after the four treatments. Compared with fish sampled immediately on capture, all treatments resulted in elevated plasma lactate and cortisol concentrations. After air exposure, plasma osmolality was elevated and reflexes were significantly impaired relative to the control and injured treatments. Injured fish exhibited reduced short-term migration speed by 3.2 km/d and had a 14.5% reduced survival to subnatal watersheds compared to controls. The 15-min facilitated recovery improved reflex assessment relative to fish released immediately but did not affect survival. We suggest that in sockeye salmon migrating in cool water temperatures (∼13°-16°C), delayed mortality can result from injury and air exposure, perhaps through sublethal stress, and that injury created additive delayed mortality likely via secondary infections.
Fish Ecology and Conservation Physiology Laboratory, Carleton University, Department of Biology, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada; 2LGL Environmental Research, Sidney, British Columbia V8L 3Y8, Canada; 3Pacific Salmon Ecology and Conservation Laboratory, Department of Forest Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada; 4Department of Biology, Carleton University, Ottawa, Ontario K1S 5B8, Canada; 5Fisheries and Oceans Canada, Science Branch, Pacific Region, Cooperative Resource Management Institute, School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia V6T 1Z4, Canada; 6Department of Zoology and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
Vivian M
VM
Nguyen
Eduardo G
EG
Martins
Dave
D
Robichaud
Graham D
GD
Raby
Michael R
MR
Donaldson
Andrew G
AG
Lotto
William G
WG
Willmore
David A
DA
Patterson
Anthony P
AP
Farrell
Scott G
SG
Hinch
Steven J
SJ
Cooke
D025041:Animal Migration; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001955:British Columbia; D003247:Conservation of Natural Resources; D005398:Fisheries; D006854:Hydrocortisone / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008136:Longevity; D009994:Osmolar Concentration; D011897:Random Allocation; D045483:Rivers; D012474:Salmon / Q000293:injuries / Q000502:physiology*; D013312:Stress, Physiological; D013997:Time Factors
D019344:Lactic Acid; D006854:Hydrocortisone