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Coastal Cutthroat Trout Genetics Study

Wild Fish Conservancy assists with a coastal cutthroat trout genetics study in the Salish Sea’s San Juan archipelago.

San Juan cutts 1Coastal cutthroat trout.  Beautiful, enigmatic, and one of the most diverse of our Pacific salmonids.  From the Kenai Peninsula in Alaska to northern California, some (resident) populations stay in small streams and rivers year-round, while others migrate downstream to forage along the saltwater shores, moving between saltwater and streams throughout their lives.  All are born, and spawn, in freshwater – and therefore the health and integrity of the populations are susceptible to instream habitat and water quality degradation; ponds, dams, and blocking culverts that are man-made barriers to migration; inadequate instream flows resulting from unpermitted withdrawals and over-allocation of limited water resources; and competition from introduced non-native fish species.

During summer 2014 Wild Fish Conservancy was contracted by Long Live the Kings to assist with a coastal cutthroat trout genetics study in the Salish Sea’s San Juan archipelago. Funding for the project is provided by the SeaDoc Society, and collaborators include Kwiaht and the Washington Department of Fish and Wildlife. Building on WFC’s earlier fish species composition and distribution surveys in the San Juan Islands, the study will characterize the population genetics of coastal cutthroat trout in two watersheds on Orcas Island and one on San Juan Island.  

Between June and September, the research team sampled fifty cutthroat trout from each of the three watersheds.  From each of the 150 fish, the survey team carefully collected length and weight data as well as a small tissue sample (fin clip) for genetic analysis.  The results of the genetic analyses will help describe the genetic relationship between the cutthroat within and among each of the three watersheds.  In addition to the tissue sample, the team collected a sample of scales from each fish to identify the age of the fish and whether fish sampled were resident or sea-run.  Each cutthroat was released unharmed at the site of capture.  The study will also describe co-occurring fish species, which included native sculpin, juvenile coho and Chinook salmon, and non-native brook trout.

Data collected on cutthroat spawn timing will be used to identify differences and similarities in behavior, and photographs of each fish sampled will allow comparisons of physical differences in the shape, spotting, and coloration of fish from each of the watersheds.  The Washington Department of Fish and Wildlife will perform the genetic analyses in the coming months; a final report is expected in 2015.

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