Exceptionally high mortality of adult female salmon: a large-scale pattern and a conservation concern

In recent decades, the relative proportion of female sockeye salmon (Oncorhynchus nerka) on spawning grounds of several British Columbia populations has declined. Coincident with the decline has been large changes to oceanic, estuarine, and river migration environments. Over the past 30 years, numer...

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Bibliographic Details
Published in:Canadian journal of fisheries and aquatic sciences 2021-06, Vol.78 (6), p.639-654
Main Authors: Hinch, Scott G, Bett, Nolan N, Eliason, Erika J, Farrell, Anthony P, Cooke, Steven J, Patterson, David A
Format: Article
Language:English
Subjects:
Confinement
Distribution
Estuaries
Fish conservation
Fluid dynamics
High temperature
Mortality
Oncorhynchus kisutch
Oncorhynchus nerka
Oncorhynchus tshawytscha
Physiological aspects
Physiological effects
Populations
Protection and preservation
Rivers
Salmon
Salmoniformes
Sockeye salmon
Spawning
Spawning grounds
Stress (physiology)
Telemetry
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Summary:In recent decades, the relative proportion of female sockeye salmon (Oncorhynchus nerka) on spawning grounds of several British Columbia populations has declined. Coincident with the decline has been large changes to oceanic, estuarine, and river migration environments. Over the past 30 years, numerous telemetry tracking and laboratory studies have examined mortality of adult Fraser River sockeye salmon during ocean and freshwater migrations. We reviewed 19 studies that provided 40 situations where male and female mortality could be directly compared. Female mortality averaged 2.1 times greater than that of males and up to eightfold higher. High female mortality was also evident in migrating coho salmon (Oncorhynchus kisutch) and Chinook salmon (Oncorhynchus tshawytscha) and for sockeye salmon in other systems. Female mortality was highest when migration conditions were challenging (e.g., high or turbulent flows, high temperatures, confinement, or handling) and towards end of river migration. We review mechanisms for differential mortality, including energy exhaustion, cardiac performance, physiological stress, and immune factors. Female-specific mortality will become even more pronounced in coming years as ocean and riverine conditions continue to change.
ISSN:0706-652X
1205-7533
DOI:10.1139/cjfas-2020-0385