The stress response predicts migration failure but not migration rate in a semelparous fish.
Recent findings from iteroparous species suggest that glucocorticoid secretion following acute stress can mediate behavior and survival strategies, ultimately influencing fitness. However, these correlates of the stress response may not exist in semelparous animals given the inability to maximize fitness by delaying reproduction. We measured baseline and stress-induced cortisol concentrations in semelparous sockeye salmon (Oncorhynchus nerka) following exposure to an acute stressor at the mouth of the Fraser River in British Columbia. The homing fish were then radio-tagged and tracked throughout their in-river migration. Findings reveal that the stress response (i.e. change from baseline to stress-induced cortisol) was predictive of mortality; fish failing to leave the release site had a significantly greater stress response (mean±SE=1004.0±75.3ng/mL) compared to fish capable of successfully migrating beyond one of the most difficult areas of passage over 100 river kilometers upstream (mean±SE=780.7±66.7ng/mL). However, there were no associations between swimming behaviors, both immediately following release and to last point of detection, and the stress response. This study also introduced an unique method of tagging migrating salmon that allows for rapid capture and sampling and thus provides the first assessment of true baseline cortisol concentrations at river-entry for migrating Pacific salmon in the wild. Results show the stress response to be linked to survival in a semelparous species and therefore set the stage for further exploration into how the evolutionary theories underlying relationships between stress responsiveness and fitness may differ between semelparous and iteroparous species.
Fish Ecology and Conservation Physiology Laboratory, Biology Department, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada. Electronic address: Katrina.vcook@gmail.com.
Katrina V
KV
Cook
Centre for Applied Conservation Research, Department of Forest Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada.
Glenn T
GT
Crossin
Fisheries & Oceans Canada, Science Branch, Pacific Region, Cooperative Resources Management Institute, School of Resource and Environmental Management, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
David A
DA
Patterson
Centre for Applied Conservation Research, Department of Forest Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada.
Scott G
SG
Hinch
Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5, Canada.
Kathleen M
KM
Gilmour
Fish Ecology and Conservation Physiology Laboratory, Biology Department, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada; Institute of Environmental Science, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
Steven J
SJ
Cooke
D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D001955:British Columbia; D005843:Geography; D006854:Hydrocortisone / Q000097:blood; D045483:Rivers; D012474:Salmon / Q000097:blood / Q000502:physiology*; D013312:Stress, Physiological
D006854:Hydrocortisone
Cortisol; Glucocorticoid secretion; Migration; Oncorhynchus nerka; Sockeye salmon; Stress response