Interpopulation variation in growth, CTMax and metabolism among seasonal phenologies of Chinook Salmon

Conservation of species facing environmental change requires an
understanding of interpopulation physiological variation. However,
physiological data is often scarce and therefore pooled across populations
and species, erasing potentially important variability between
populations. Interpopulation variation in thermal physiology has been
observed within the Salmonidae family, although it has not been associated
with seasonally distinct migratory phenotypes (i.e., seasonal runs). To
resolve whether thermal physiology is associated with life-history
strategy we acclimated four Sacramento River juvenile Chinook salmon
populations (Coleman fall-run, Feather River fall- and spring-run and
Sacramento River Winter-run) exhibiting different seasonal migratory
phenotypes (fall-, spring- and winter-run), at 11, 16 and 20°C and
assessed variation in growth rate, critical thermal maxima and
temperature-dependent metabolic traits. We identified population
differences in the physiological parameters measured and found compelling
evidence that the critically endangered and endemic Sacramento River
winter-run Chinook population exhibits thermal physiology associated with
its early-migration life-history strategy. Acclimation to warm
temperatures limited the growth and metabolic capacity of winter-run
Chinook salmon, highlighting the risk of future environmental warming to
this endemic population.