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<br />stem Bighorn River from the town of Kirby downstream was not considered as historical Yellowstone <br />cutthroat habitat, even though cutthroat trout may have been present to a limited extent. <br /> <br />Approximately 4,624 miles of stream habitat, in Wyoming, are presently inhabited by Yellowstone <br />cutthroat trout (Table 5). Here again the mileage estimates are likely inflated as a result of the <br />information from the Bighorn and Clarks Fork basins and how that information was used. Included <br />within the total are 1,751 miles of stream habitat occupied by the "fine spotted" form. The current <br />extent of "fine spotted" Yellowstone cutthroat occupancy has actually increased as a result of stocking <br />of hatChery reared fish into habitats outside of the "fine spot" range. Based on this information, <br />approximately 42% of the historic habitat was felt to be currently occupied by Yellowstone cutthroat <br />trout. Even though this occupancy value appears to be relatively high, caution should again be <br />applied before arriving at any final conclusions. For most sub-basins, genetic integrity has been <br />determined by meristic and/or visual techniques which have limited ability to detect hybridization with <br />rainbow trout. Coupled with this is the acknowledgement that 96% of the sub-basins have exotic <br />species present, including rainbow trout, or they have received past plants of rainbow trout (Table <br />6). Until a more detailed assessment of genetic purity is undertaken it is probable that current <br />occupancy estimates are too high. The origins of existing populations were identified as being <br />remnant of historic populations or they were linked to recent hatchery introductions, as in the case <br />of "fine spotted" Yellowstone cutthroat trout. Within the sub-basin areas, the majority of cutthroat trout <br />populations were determined to be secure and stable (Table 6), with a lesser number of sub-basins <br />having populations described as being stable but at risk. Even though twenty four of the sub-basins <br />indicated the presence of exotic trout species, only twelve indicated a concern that exotic species <br />could be a threat to cutthroat trout. <br /> <br />Historical references of aquatic habitat conditions, within Wyoming, are limited to information sup- <br />plied by naturalist visits directed by the U.S. Commission of Fish and Fisheries (Jordan 1891, <br />Evermann 1891, Gilbert and Evermann 1894). These early accounts of habitat condition were usually <br />qualitative, but they provide a reference point for comparison. Jordan (1891) alluded to the numerous <br />falls, within the Yellowstone National Park area, which maintained a substantial amount of area <br />(estimated at 1500 sq. mi.) in a fishless condition. Jordan also mentioned the influence of thermal <br />features on fish and water quality. Evermann's (1891) habitat descriptions of the Snake River above <br />Jackson Lake (President's Camp) and within the Yellowstone River drainage included references to <br />water temperatures, water clarity , substrate composition and, in some instances, width and depth <br />characteristics. Gilbert and Evermann (1894) revisited the upper Snake River in 1892 and they <br />provided similar qualitative observations. For all habitats supporting trout, historic abundance obser- <br />vations would likely correlate with excellent habitat. <br /> <br />Assessment of current habitat conditions in Wyoming indicates a slightly different picture with only <br />a minor portion of the sub-basins reflecting excellent habitat condition. A substantial number of the <br />sub-basins reflected conditions ranging from good to poor (Table 7). Trends associated with current <br />habitat condition were generally considered to be stable for both the habitats on National Forest <br />administered land and those found in other ownership. The factors affecting aquatic habitat quality <br />and some of the associated land uses are identified in Table 8. It is important to note that information <br />contained in Tables 7 and 8 may at times seem inconsistent. For some sub-basins more than one <br />condition and/or trend was identified and for other sub-basins condition and/or trend may have been <br />omitted. The same is true for the information associated with factors linked to degradation and the <br />land-use activities associated with those factors. Grazing, mining, logging, road construction and <br />agriculture were the land-uses identified as contributing to channel dewatering, channel modification, <br />limited large wood and increased sediment. <br /> <br />19 <br />