Class II sport fishery value. T' is was due to decreased 

 aesthetics resulting from Interstate 90 bordering the river, and 

 lower use levels. As the river continues downstream through 

 Billings to the Bighorn River confluence, the waters slow, 

 turbidity increases, and temperature rises, causing trout 

 populations to disappear. The river received a Class III sport 

 fishery value in this 81-mile reach, with sauger, channel catfish 

 and burbot up to 10 pounds contributing to the sport fishery. 



Major tributaries to the Yellowstone receiving a Class II 

 sport fishery included reaches of Rock Creek and the Boulder 

 River, and the entire Stillwater River, the latter two of which 

 are threatened by the largest platinum mining operation in the 

 country. The Shields River, the only northern tributary, received 

 a Class III throughout its length due to a lack of large trout, 

 low fishing pressure and an average aesthetics rating. 



The Bighorn River of southeastern Montana received a Class I 

 resource value in its first 31 miles below Yellowtail Dam. Until 

 1965, the Bighorn was a silty prairie stream with a sauger, 

 catfish and burbot fishery. After the construction of Yellowtail 

 Dam 84 miles above the mouth, waters emerging from the dam were 

 cold, clear and productive. Trout production exploded and a trout 

 stream of national importance was created. Although the brown 

 trout population of the upper Bighorn has been found to fluctuate 

 with environmental factors, including flows, water temperature and 

 gas supersaturation, the river below the dam holds 5,000 to 10,000 

 trout per mile. The latest estimate indicated 5,000 of those were 

 between 15 and 18 inches and 500 were larger than 18 inches, the 

 greatest biomass of any trout river in the state. As a result of 

 these outstanding fisheries and precipitated somewhat by an 85 

 percent increase in angler use between 1985 and 1986, a river 

 management plan for the Bighorn was drafted by the MDFWP in 1987, 

 with extensive public involvement. 



Wildlife 



The upper Yellowstone River drainage supports a valuable 

 wildlife resource. Nineteen (40 percent) of its 48 river units 

 received Class II final resource values, and two others along the 

 Big Horn and East and West Rosebud Creeks received Class I final 

 resource values (Table 57). In all, 38 percent of the river 

 basins received Class I or Class II habitat ratings. About 33 

 percent achieved Class I or II species ratings. 



Substantial wildlife values resulted from extensive riparian 

 zones found along five Yellowstone main stem units and several 

 important tributaries such as the Sweetgrass and Boulder Rivers. 

 Although extensive development has occurred along most of the 

 Yellowstone, its lower 142 miles from Bridger Creek to the 

 Bighorn, earned an outstanding value because of extensive gallery 

 forests, abundant backwater sloughs and wetlands, and islands. 



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