Introduction
The greenback cutthroat trout (Oncorhynchus clarki stomias) is native to the mountain and foothill waters of the South Platte and Arkansas river basins in Colorado (Behnke and Zarn 1976). This taxon was abundant in the late 19th century when large numbers of European immigrants arrived in and along the Front Range of Colorado. At that time, fish from 2 to 4.5 kg were relatively common historically and were notable for their extensive migrations to spawn, rear, and overwinter (Wiltzius 1985). Subsequent mining in the Arkansas River basin and southern tributaries of the South Platte River (Ubbelohde and others 1976) introduced large amounts of sediment and toxic runoff that reduced or exterminated many greenback cutthroat trout populations, as did agricultural development in river valleys because of water diversions (Jordan 1891). Furthermore, harvest of greenback cutthroat trout, often with explosives, was sufficiently widespread to have eliminated additional populations (Wiltzius 1985). Although by 1919 greenback cutthroat trout were still found in many tributaries of the upper Arkansas River (Carhart 1950), there are no reports on the status of populations in other locations at that time.
Concomitant with the extensive commercial and recreational harvest of greenback cutthroat trout in the late 1880s was the appearance of private and government fish hatcheries in Colorado. Initially, greenback cutthroat trout were frequently cultured, but their use diminished by the 1900s (Wiltzius 1985), possibly because few wild fish were still extant. Brook trout (Salvelinus fontinalis) were the first nonnative salmonids cultured in Colorado in 1872, but other species soon followed. Because cutthroat trout are often replaced by brook trout and brown trout (Salmo trutta) and readily hybridize with rainbow trout (O. mykiss) and nonindigenous subspecies of cutthroat trout (Behnke 1992; Behnke and Zarn 1976; Wang and White 1994), introductions of nonnative trout, or the invasion of stocked populations into new waters, are believed to have eliminated greenback cutthroat trout from nearly all of their remaining historical range.
By the 1930s, the subspecies was considered extinct (Green 1937), but an apparently pure population in a portion of the Big Thompson River in Rocky Mountain National Park was found in 1957 (U.S. Bureau of Sport Fisheries and Wildlife 1957). Though this population was later thought to be introgressed with nonnative species, additional populations detected in 1965 and 1970 were deemed pure. Consequently, the greenback cutthroat trout was listed as endangered in 1973 under the U.S. Endangered Species Act, and downlisted to threatened in 1978 (USFWS 1998). The original recovery plan was completed in 1977 (Greenback Cutthroat Trout Recovery Team 1977), and revisions were adopted in 1983 (USFWS 1983) and 1998 (USFWS 1998).
Although surveys for remaining populations continue and are occasionally successful, most recovery efforts have focused on establishing new populations (USFWS 1998). By 1999, introductions had been attempted in 44 waters (Harig and others 2000). Many of these attempts have been successful, to the extent that the greenback cutthroat trout may soon be proposed for delisting under the Endangered Species Act within all or part of its historical range (USFWS 1998).
A requirement for delisting is the completion of a long-term plan to guide management, and central to that plan is a compilation of the conservation and recovery history of this subspecies. Although some of this information is readily obtainable (USFWS 1998 and references therein), many data relevant to the discovery, establishment, and monitoring of wild populations and the establishment, maintenance, and distribution of hatchery broodstocks are difficult to find. Consequently, our objective was to compile existing data from 1957 to 1999 on population characteristics of greenback cutthroat trout in waters used for recovery and on hatchery participation in recovery. Additional information on habitat surveys, habitat modification, and fishing regulations was excluded. The bibliography contains materials cited in this document as well as available literature pertinent to the biology and recovery of greenback cutthroat trout.
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Title: RMRS-GTR-88WWW:
Introduction
Electronic Publish Date: January 2002
Last Update: January
20, 2010