The Central Valley of California historically contained a diverse tapestry of freshwater habitats, from the salty marshes of the lower estuary to the ice-cold mountain streams of the Sierras. Chinook salmon (Oncorhynchus tshawytscha) developed a remarkable array of strategies to take advantage of these varied habitats, but as habitats have been altered and fragmented, so too has the diversity of Chinook populations. In particular, the Chinook that relied on coldwater habitats to survive in rivers through the summer – such as spring-run Chinook – have lost access to much of their historic range due to dams, and consequently have experienced precipitous declines. As the diversity of Chinook populations diminishes, so does the species’ resilience and adaptability. But all hope is not lost – the findings of a recent study examining the genetics of Chinook in a very modified river in the Sacramento Basin (Hugentobler et al. 2024) suggest that the diversity of these salmon may be more persistent than previously thought.