Bull trout are one of the management indicator species for the forest. Population monitoring efforts are undertaken every year to provide an assessment of forest health. They were selected because they are dependent upon specific habitat conditions and are sensitive to habitat changes. Bull trout are only found in parts of the Salmon, Boise, and Payette river watersheds on the Fairfield District and the SNRA. The forest is home to the longest salmon migration in the continental United States, but with the damming of the Columbia River, salmon populations have collapsed. Redfish Lake was named for the sockeye salmon that would return to breed in the lake and its tributaries and historically had 10,000 to 35,000 adult fish return to the lake annually. Between 1990 and 1998 a total of 16 adult fish returned to Redfish Lake, but populations have recovered somewhat, and in 2014 approximately 1400 adult fish returned, up from 1100 in 2011. Repeated efforts to repopulate the sockeye salmon have taken place in the Columbia River watershed, and in 2008 the first salmon season in 31 years was held for chinook salmon in the upper Salmon River. Brook trout have been introduced to the forest and are now an invasive species that compete with the threatened bull trout. The Wood River sculpin is a fish species that is endemic to the Big Wood River and its tributaries on the Ketchum District and is listed as vulnerable by the International Union for the Conservation of Nature (IUCN) Red List. Rainbow trout, cutthroat trout, and mountain whitefish are all native to portions of the forest waterways.