Chinook salmon is a native anadromous species and the largest of Pacific salmon. In California adults migrate throughout the year as four seasonal runs. Commonly referred to as a cold-water species they are currently facing population declines due to multiple factors such such as anthropogenic habitat alterations (e.g. dams) and a changing climate (e.g. warming water temperature). Our lab aims to understand their physiology to better inform management actions taken in California and across the west-coast.

The ash left in the wake of wildfires presents an ecological concern. Indeed, when introduced to aquatic systems by means of precipitation or snowmelts, the ash induces a rapid increase in water pH—a phenomenon referred to as environmental alkalinization. Such a spike in pH, coupled with elevated water temperature following wildfires, can pose significant ionic, osmotic, and acid-base (IOA-B) challenges to aquatic organisms, particularly when habitats prone to wildfires overlap with important spawning/rearing grounds (e.g. Chinook salmon in the San Francisco-San Joaquin Delta). Click here to read more about the study we conducted to investigate this phenomenon.

Due to their life-history strategy, Chinook salmon exist as a collection of populations, particular to their river systems. How these populations differ from each other can inform how we understand salmonid adaptation as well as provide insight into how to best manage this plastic species. Previous graduate student, Dr. Ken Zillig, looked specifically at temperature, and how different populations of Chinook salmon may exhibit varying thermal physiologies and whether these variations are a result of local adaptation.

His work explored populations from California, Oregon and Washington and found signals of local adaptation both among populations native to California and several fall-run populations from the Columbia River to the Sacramento. He hopes that these results open the door to more place-based management of Chinook salmon to better support remaining physiological diversity. You can read more here.

Spring-run hatchery Chinook salmon smolts released in the San Joaquin river have been experiencing high mortality rates and low returns. Smolts have been held in cages in locations shown to be areas of high mortality by previous telemetry studies for acclimatization and then physiological testing of mRNA expression of sublethal stress and possible pathogen infections. By combining assessments of pathogen load and stress markers linked to water quality, we should be able to glean greater insight into potential mechanisms underlying observed mortality patterns. It is hypothesized that higher mortality rates (outside the initial release) are due to accumulated sub-lethal stress stemming from degrading environmental conditions in the San Joaquin River.