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road construction, mining, and grazing, is seen as the major contributor to habitat degradation (Rieman and Apperson 1989). Montana The historic range of westslope cutthroat trout in Montana is the upper Missouri River drainage and the headwaters of the Marias, Judith, Musselshell, and Milk rivers east of the Continental Divide, the South Saskatchewan drainage, and the upper Columbia River basin west of the Continental Divide. Cutthroat trout were first recorded in 1805 by the Lewis and Clark expedition near the "Great Falls of the Missouri" (Behnke 1992). Trotter and Bisson (1988) reviewed early western explorers' journals and concluded that cutthroat trout were extremely abundant where they occurred. Uknes and Graham (1988) summarized the status and management of westslope cutthroat and estimated that the species occupied 27% of its historic range in Montana Biologists using the Montana Rivers Information System (MRIS) estimate that in Montana, westslope cutthroat trout occupy 19% of their historic range of 57,184 stream miles as derived from the 1:100k hydrography layer. Estimates were based upon the 1994 update of the database and historic occupancy assumed this subspecies occurred in all perennial streams, which may be an overestimate. Further refinement of this assumption is needed through record searches, interviews etc. to more realistically document historic range. Westslope cutthroat trout populations in Montana are abundant in 2% of their historic range and would be considered viable (abundant and common) in 8% of their historic range. Of the remaining populations, 11 % are abundant and 45% are considered viable. Northwestern Montana is considered the stronghold for genetically pure and strong populations. The distribution and abundance of this subspecies is continuing to decline across the state. Decline of wests lope cutthroat trout populations is not a recent phenomenon; Hanzel (1959) concluded that this subspecies was restricted to headwa- ter streams where they originally occurred and most populations were in streams above barriers. In 1988, Uknes and Graham (1988) estimated that genetically pure populations were present in about 2.5% of the historic range and 9% of the current range. Currently, about 33% of the remaining 10,830 stream miles occupied by wests lope cutthroat trout have have been electrophoretically sampled, of those tested, 59% are pure. In other words, about 20% of the current populations are known to be pure. Another 13% are suspected to be pure without potential introgression, but remain untested. A much higher proportion of pure populations have been tested because biologists have emphasized testing of those waters where pure populations are suspected. Biologists with the Forest Service, Bureau of Land Management, and Montana Department of Fish, Wildlife, and Parks are conducting a broad scale assessment on upper Missouri River basin wests- lope cutthroat populations. They have found that westslope cutthroat trout occupy about 7% of their historic range while pure populations exist in about 1 % of their historic range. As a general rule, populations have been isolated into small, fragmented headwater streams (Brad Shepard, Montana Fish, Wildlife and Parks, personal communication). Reasons for decline of westslope cutthroat trout populations in Montana have not been quantified, however, biologists identified factors similar to those in Idaho. Liknes and Graham (1988) feared that hybridization, mainly with rainbow trout, was the greatest factor, but habitat degradation, angling, and competition also contribute to. decline. Table 1 presents westslope cutthroat range, abundance, and genetic analysis in Montana. 4