The state fish of California is a the golden trout, which is typically found in Golden Trout Creek, its tributaries, Kern River, South Fork Kern River, and Lake Isabella. The golden trout, scientifically known as Onchorhynchus aguabonita, was designated the state fish of California in 1947. While programs to support the species were once considered to have successfully expanded the golden trout's range throughout the Sierra Nevadas and even into other states, experts now believe that the genetically pure golden trout may be endangered due to interbreeding with other trout species, notably the rainbow trout. The golden trout is believed to be a sub-species of the rainbow trout, and may have evolved from the Sacramento San-Joaquin redband rainbow trout. The golden trout's 300,000-acre (121,405-hectare) habitat was officially protected by the state of California in 1978, and the species was added to the United States Fish and Wildlife Service's Endangered Species List in 1991.
The California golden trout is considered by many to be one of the most colorful and visually striking species of trout. The state fish of California typically has an olive-green dorsal stripe. Its abdomen and flanks can range in color from bright red to vibrant gold. The colors are believed to grow brighter during spawning, which usually occurs in the spring. The golden trout mostly feeds on insects and their larvae.
Though these fish have been introduced into high-altitude waters across the North American west, they are considered native to about 450 miles (724 kilometers) of the South Fork Kern River and Golden Trout Creek. These fish are believed ideally suited to the cold waters found at high elevations, generally above 6,800 feet (2072.6 meters). These generally slow-growing fish have an average life span of about seven years, and usually reach an average size of about 1 pound (0.45 kilograms).
These fish have historically been relatively limited in their range, and are now considered in serious danger of extinction. Threats to the California golden trout include livestock grazing and low quality of land management, which have damaged the golden trout's natural habitat. The state fish of California is also believed to be especially vulnerable to hybridization, especially with non-native trout species that have been introduced to the area. Efforts have been made in the past to support the golden trout population and increase its range, but these efforts appear to have contributed to the hybridization of the species.