My second dissertation chapter has now been published in the Canadian Journal of Fisheries and Aquatic Sciences and is entitled Interpopulation variation in thermal physiology among seasonal runs of Chinook salmon. This paper looks at the thermal physiology of four populations of Chinook salmon from the Central Valley of California. These four populations differ in their seasonal run-type and included two fall-run (Coleman population and Feather River population), a spring-run (also from the Feather River) and the critically endangered winter-run. We find that the juveniles of the Winter-run population exhibit thermal physiology well suited to their historical habitats (cold, high elevation, spring-fed systems). This distinct physiology supports the poor performance of winter-run salmonids in the wild. Winter-run eggs are laid in early summer and therefore embryos and juveniles must weather the summer heat extremes. Historically, they would have spent this time in cold, spring fed rivers, but now are limited by Shasta reservoir to the Sacramento River outside Redding, CA where air temperatures can climb in to the triple digits.
These data are useful when considering the management and conservation of different populations of Chinook salmon. Differences in thermal physiology, growth rate and metabolic capacity can lead to differences in response to environmental conditions, and even management actions. Therefore understanding these differences can allow resources managers to better predict how different populations of Chinook will respond to changes in their environment.