California’s Central Valley is home to four runs of Chinook salmon: spring, fall, late-fall, and winter. Spring-run and winter-run Chinook salmon are currently listed as threatened or endangered under the Endangered Species Act. From climate change to loss of habitat, salmon are faced with a number of threats, and one of the latest to emerge in recent years is a thiamine deficiency. Thiamine is vitamin B1, and it is a crucial vitamin for neurons and immune systems in salmon. Evidence of a thiamine deficiency in spring-run salmon started showing up in 2020. According to Brett Harvey, Department of Water Resources (DWR) environmental program manager, salmon typically get adequate levels of thiamine from their food supply in the ocean, but for the last several years that hasn’t been happening due to changes in the ocean food web.