The Sacramento River has a diverse range of Chinook salmon due to varying run timings, with other anadromous fish also present. Specialized habitats and geography in California have allowed for four salmon species to thrive, including the spring-run Chinook salmon native to the San Joaquin and Sacramento River systems. The Sacramento River has two main races of Chinook salmon, with the fall-run being the most numerous historically. The Chinook salmon is the largest and least abundant Pacific salmon species. Historically, winter-run Chinook salmon were found in various tributaries of the Sacramento River, but have since faced extinction threats. These salmon have been identified as one of the most at-risk species and are the focus of conservation efforts.