Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 81 to >300
Comments: Hovingh (2004) found it in the upper Snake River in Wyoming and Idaho, upper Bear River in Wyoming, and Malheur Basin in Oregon. It was recently confirmed in the Middle Fork John Day River in Oregon (Brim Box et al., 2003; 2006). In Montana, it is found throughout the Missouri River headwaters, Kootenai River, Flathead River, Clark Fork River, Madison River, and Jefferson River (Gangloff and Gustafson, 2000) but Stagliano (2010) found 25 of the ~40 reported sites were extirpated or not viable and only 5 new viable sites were found. In Idaho, historical range includes sites in the Snake, Coeur d'Alene, Lost, and Salmon River drianages (Frest and Johannes, 1999) and populations persist in north Idaho in the Coeur d'Alene, St. Joe, and St. Maries Rivers (Stagliano et al., 2007). In central Idaho, populations with good viability occur in the Clearwater, Selway, Lochsa, Pahsimeroi, Lost, Salmon, and Little Salmon Rivers and in Hells Canyon while in south Idaho, populations are thought extant in the upper tributaries of the Snake River, including the Blackfoot River (Frest and Johannes, 1997). Lysne and Pierce (2009) found it rare in Crystal Creek-Spring Creek, Blaine Co., Idaho. Populations exist in the Lower Salmon River, Idaho (Vannote and Minshall, 1982; Davis and Muehlenbachs, 2001). It was believed extirpated in Utah until it was recently found in a tributary of the Weber River near Provo (C. Tait, USFS, pers. comm., 2010). Declines were noted in streams in western Washington (Hastie and Toy, 2008). Populations are also known from throughout California (see Howard and Cuffey, 2006), including the Pit River (Spring Rivers Ecological Sciences, 2001) and at least historically in the Truckee River (Murphy, 1942). A recent survey of 115 sites in the Plumas, Tahoe, and Eldorado National Forests plus Lake Tahoe Basin management unit found it in 15 sites (10 of 70+ streams) (Howard, 2008). Recently in California: McCloud River, Hat Creek, Pit and S Fork Pit River, Spanish Creek, Truckee River, Scott River, S Fork Eel River, Shasta River, San Antonio Creek, N Fork Stanislaus River, N, M, and S Fork Tuolumne River, S Fork American River, and M Fork Feather River (Howard, 2010). It is sparingly documented in southeast Alaska and questionably the Chukotski Peninsula in Russia (Baxter, 1987); including Revillagigedo Island and north to Naha Bay at 55 degrees latitude at Naha Bay, Alaska (Gustafson et al., 1997) and Prince of Wales Island (Metcalfe-Smith and Cudmore-Vokey, 2004). In Wyoming, Beetle (1989) lists occurrences in streams in Lincoln, Sublette, Teton, and Uinta Cos.; while Cvancara (2005) lists occurrences in the Snake and Missouri River drainages in Yellowstone National Park, the Snake River drainage in Teton, Lincoln, and Sublette Cos., and Bear River drainage in Lincoln and Uinta Co. Sites in the upper Columbia River in Washington still maintain viable populations (WA NHP, pers. comm., 2007). Taylor (1952) cites occurrences in the Snake Headwaters, Upper Snake (into Idaho), Upper Yellowstone, and Missouri headwaters (into Montana). In Canada, healthy populations occur in northern British Columbia and on southern Vancouver Island (Metcalfe-Smith and Cudmore-Vokey, 2004). In British Columbia, it occurs on the islands and as far east on the mainland as the Kettle River and as far north as the Babine Lake area at 55 deg latitude (Metcalfe-Smith and Cudmore-Vokey, 2004). Clarke (1981) cites northern distribution as southern interior of British Columbia, and farther north near the coast to Revillagigedo Island in southern Alaska.
