Growth of Lahontan cutthroat trout from multiple sources re-introduced into Sagehen Creek, CA

Lahontan cutthroat trout Oncorhynchus clarkii henshawi have experienced massive declines in their native range and are now a threatened species under the US Endangered Species Act. A key management goal for this species is re-establishing extirpated populations using translocations and conservation hatcheries. In California USA, two broodstocks (Pilot Peak and Independence Lake) are available for reintroduction, in addition to translocations from wild and naturalized sources. Pilot Peak and Independence Lake fish are hatchery stocks derived from native fish from the Truckee River basin and used for recovery activities in the western Geographic Management Unit Areas only, specifically within the Truckee River basin. Yet suitability of these sources for re-introduction in different ecosystem types remains an open and important topic. We conducted growth experiments using Lahontan cutthroat trout stocked into Sagehen Creek, CA, USA. Experiments evaluated both available broodstocks and a smaller sample of fish translocated representing a naturalized population of unknown origin from a nearby creek. Fish from the Independence Lake source had significantly higher growth in weight and length compared to the other sources. Further, Independence Lake fish were the only stock that gained weight on average over the duration of the experiment. Our experiments suggest fish from the Independence Lake brood stock should be considered in reintroduction efforts.