Coherent population dynamics associated with sockeye salmon juvenile life history strategies




Freshwater, Cameron
Trudel, Marc
Juanes, Francis
Burke, Brian
Scheuerell, Mark
Grant, Sue

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Canadian Journal of Fisheries and Aquatic Sciences


We examined how individual processes contribute to a latitudinal gradient in body size within populations of migrating juvenile Sockeye Salmon (Oncorhynchus nerka) while simultaneously testing for size-selective mortality, a potentially confounding population scale process. Using otolith microstructure techniques and structural equation modeling, we determined that ocean entry size and phenology had strong, direct effects on size at capture. Population identity and freshwater age also had strong indirect effects, moderated by size at entry. Conversely, marine growth rates immediately after entry or before capture were relatively weak predictors of size during migration. We next tested for shifts in size distribution indicative of selective mortality, but detected no evidence of smaller individuals experiencing lower survival during early marine migrations. These results indicate that the migratory distributions of juvenile Sockeye Salmon are influenced by body size and that this variation is predominantly driven by traits present prior to freshwater outmigration, rather than marine growth or differential survival. We suggest integrating individual variation in migratory characteristics with the effects of environmental conditions experienced en route to provide an improved understanding of migratory species.



body size, migration, size-selective mortality, structural equation modeling


Freshwater, C., Burke, B., Scheuerell, M., Grant, S., Trudel, M., & Juanes, F. (2018). Coherent population dynamics associated with sockeye salmon juvenile life history strategies. Canadian Journal of Fisheries and Aquatic Sciences, 75(8).