Kern River Rainbow Trout

Kern River rainbow trout are endemic to the Kern River and tributaries, from Lake Isabella upstream to the headwaters (Tulare County). Some streams within this drainage have barriers to upstream fish movement and do not contain populations of Kern River rainbow trout above these barriers. These include the watersheds of the other two golden trout: the Little Kern River, South Fork Kern River, and Golden Trout Creek. Genetic analyses revealed that trout located in the lower portion of the Kern River are highly introgressed with hatchery or coastal rainbow trout, likely from a long history of stocking this portion of the river. In the upper watershed, they appear to share genes with California golden trout.

Kern River rainbow trout were once abundant and widespread in the upper Kern Basin and grew to large sizes. As a result, they were subject to intensive removal by angling. Since the 19th century, over-exploitation, combined with habitat degradation and, most importantly, hybridization with other trout, has reduced populations to a small fraction of historic numbers. The primary threats to remaining populations are similar to those facing other endemic trout of the southern Sierra, which center on interactions with non-native trout and habitat loss from grazing, logging, and roads.

With the ongoing uncertainties about their taxonomic status and how best to conserve and restore a subspecies that exists in a watershed where natural and human movement of fishes has occurred, the conservation of Kern River rainbow trout is a complicated endeavor. The subspecies was thought to have disappeared through hybridization with introduced, non-native rainbow trout, although a natural invasion of coastal rainbow trout may have occurred.

CDFW recently conducted surveys throughout the watershed in search of “pure” Kern River rainbow trout. Genetic studies found a population in a headwater lake to Big Arroyo. Steps are being taken to capture a portion of this population and rear them in a hatchery. If successful, these fish may be used to support sport fisheries in the lower Kern River and replace stocking of rainbow trout. To further protect the genetic integrity of Kern River rainbow trout, all hatchery rainbow trout stocked into the Kern River have undergone a process to make them sterile. An Upper Kern Basin Fishery Management Plan was written to restore, protect, and enhance the native Kern River rainbow trout populations and prevent them from becoming an endangered species.

Kern River rainbow trout are classified by the U.S. Fish and Wildlife Service as a candidate species for listing under the Endangered Species Act. This means they may warrant additional protection but there is inadequate information to make a determination. Kern River rainbow trout are also listed as a Species of Special Concern by CDFW.