EF - 5000-200,000 square km (about 2000-80,000 square miles) - EF - As defined by the USFWS (2004), the distribution of the West Coast distinct population segment (DPS) includes the Cascade Mountains and all areas west, to the coast in Oregon and Washington; and in California, the North Coast from Mendocino County north to Oregon, east across the Klamath (Siskiyou, Trinity, and Marble) Mountains, across the southern Cascade Mountains and south through the Sierra Nevada Mountains. The mountainous areas east of the Okanogan River in Washington and the Blue Mountains west to the Ochoco National Forest in eastern Oregon are not included in this DPS due to their geographical isolation from the remainder of the DPS. However, the southern Sierra Nevada and northern California/Oregon Siskiyou populations are the only naturally occurring, known breeding populations of fishers in the Pacific region from southern British Columbia to California (USFWS 2004). Zielinski et al. (2004) mapped the current range in California.
Grinnell et al. (1937) estimated extremely low population numbers for the fisher in California at a time when trapping for the fur trade had greatly reduced populations of furbearing animals. Although it is possible that fisher populations recovered somewhat immediately following the trapping prohibitions in the 1930s and 40s, Powell and Zielinski (1994) more recently noted population declines for fisher populations in the west. Fishers are believed to be extirpated from the lower mainland of British Columbia; however, they may still occupy the higher elevations of these areas in low densities (BC Species and Ecosystems Explorer, http://srmapps.gov.bc.ca/apps/eswp/, accessed November 17, 2003). In the Pacific States, fishers were historically more likely to be found in low to mid-elevation forests up to 8,200 feet (2,500 meters ) (Grinnell et al. 1937, Schempf and White 1977, Aubry and Houston 1992). In recent decades, the scarcity of detections in Washington, Oregon, and the northern Sierra Nevada in California indicates that the fisher may be extirpated or reduced to very low numbers in much of this area (Aubry and Houston 1992, Aubry and Lewis 2003). Source: USFWS (2004).
In Washington, the fisher historically occurred both east and west of the Cascade Crest (Scheffer 1938, Aubry and Houston 1992). Lewis and Stinson (1998) concluded that, ``Based on habitat, the historical range of fishers in Washington probably included all the wet and mesic forest habitats at low to mid-elevations. The distribution of trapping reports and fisher specimens collected in Washington confirms that fishers occurred throughout the Cascades, Olympic Peninsula, and probably southwestern and northeastern Washington.'' Aubry and Houston (1992) compared current and historical records of fishers in Washington and found 88 reliable records, dating from 1955 to 1991. West of the Cascades, fishers occurred at elevations of 100 to 1800 m, with most records from below 1,000 m. On the east slope of the Cascades where precipitation is lower, fishers were recorded from 600 to 2,200 m (Aubry and Houston 1992). Similar to elsewhere in the range, the upper elevational limit may be determined by snow depth (Krohn et al. 1997). Based on a lack of recent sightings or trapping reports, the fisher is considered to be extirpated or reduced to scattered individuals in Washington (Aubry and Houston 1992, Lewis and Stinson 1998). Source: USFWS (2004).
In 2008-2010, 90 fishers were released into Olympic National Park, Washington. Reproduction by the reintroduced fishers has been documented.
Based on extensive inquiry and review of records, Aubry and Lewis (2003) found that extant fisher populations in Oregon are restricted to two disjunct and genetically isolated populations in the southwestern portion of the state: one in the northern Siskiyou Mountains of southwestern Oregon and one in the southern Cascade Range. The fishers in the Siskiyou Mountains near the California border are probably an extension of the northern California population (Aubry and Lewis 2003). The population in the southern Cascade Range is reintroduced and is descended from fishers that were translocated to Oregon from British Columbia and Minnesota (Aubry and Lewis 2003). The Oregon Cascade Range population is separated from known populations in British Columbia by more than 650 kilometers (Aubry and Lewis 2003). Source: USFWS (2004).
In eastern California, the fisher historically ranged throughout the Sierra Nevada, from Greenhorn Mountain in northern Kern County northward to the southern Cascades at Mount Shasta (Grinnell et al. 1937). In western California, it ranged from the Klamath Mountains and north Coast Range near the Oregon border southward to Lake and Marin Counties (Grinnell et al. 1937). Substantial efforts to assess the status of fishers and other forest carnivores in California using systematic grids of baited track and camera stations. indicate that fishers appear to occupy less than half of the range they did in the early 1900s in California, and this population has divided into two remnant populations that are separated by approximately 420 km (Zielinski et al. 1995), almost four times the species' maximum dispersal distance as reported by York (1996) for fishers in Massachusetts. One population is located in northwestern California and the other is in the southern Sierra Nevada Mountains. Since 1990, there have generally been no detections outside these areas except for one in 1995 in Mendocino County and one in 1995 in Plumas County (CDFG 2002, updated November 13, 2003). Failure to detect fishers in the central and northern Sierra Nevada, despite reports of their presence there by Grinnell et al. (1937) and reports from the 1960s collected by Schempf and White (1977), suggests that the fisher population in this region has declined, effectively isolating fishers in the southern Sierra Nevada from fishers in northern California (Truex et al. 1998, Lamberson et al. 2000). However, prior to the recent development of a rigorous fisher survey protocol, differences in the type and quality of data available over the previous 60-year period make interpretation of distributional changes difficult (Zielinski et al. 1995). Source: USFWS (2004).
