in 400 miles could not be rated due to insufficient fisheries 

 information (Tables 55 and 56). In the habitat and species 

 category, 12 reaches in 40 miles received a Class I, including two 

 nationally renowned spring creeks, Armstrong and Nelson, and main 

 stem essential spawning habitat. Of the 19 reaches rated Class II 

 in the habitat and species values, nine contained Yellowstone 

 cutthroat populations, but their genetic purity was unknown. Two 

 others were high-valued spring creeks, four reaches were important 

 to local communities in addition to having high species diversity, 

 and three were essential spawning streams to Class II reaches of 

 the Yellowstone. 



Surprisingly, only Crooked Creek in the Pryor Mountains 

 received a Class I species and habitat value due to the presence 

 of pure native Yellowstone cutthroat trout. The species reached 

 Montana nearly 75,000 years ago from the upper Snake River via Two 

 Ocean Pass in the southeastern corner of what is now Yellowstone 

 National Park. Once reaching the pass, the cutthroat spread 

 downstream, extending their range in all tributary streams east to 

 the Tongue River, where Lewis and Clark reported catching 800 in 

 a matter of a few days. By the late 1800s, however, fishing 

 pressure and increased water and land use had decreased the 

 populations throughout their range. By the 1950s, their range had 

 been reduced to upper river tributaries mostly in headwater areas. 



Recent genetic analysis of populations from the upper river 

 and the Shields drainage found more pure populations of cutthroat 

 trout than was previously thought. Of the 27 streams analyzed in 

 1986 and 1987, 17 contained pure populations, but none were 

 isolated from contaminating species such as rainbow trout. 



The upper Yellowstone drainage also contained 128 miles of 

 Class I sport fisheries. The upper river was tied with the lower 

 Yellowstone for the largest number of Class I sport fishery stream 

 miles in the state. Included were the 99 miles of the upper 

 Yellowstone River from the Yellowstone National Park boundary to 

 the Boulder River, the longest stretch of "blue ribbon" trout 

 stream in the state. Populations of Yellowstone cutthroat, brown 

 and rainbow trout, with numerous trophy-sized fish, the pristine 

 beauty of the Paradise Valley and a river accessible to the public 

 contributed, to the Class I sport fishery value. Recent fisheries 

 data indicate trophy-sized cutthroat are declining in the main 

 stem and recruitment is controlling the population. For the 

 Yellowstone cutthroat, a tributary spawner, dewatering of spawning 

 habitat appears to be the major problem reducing recruitment. 

 Largest main stem cutthroat populations are found in the vicinity 

 of tributaries unaffected by irrigation withdrawals. 



The sport fishery value decreases as the river journeys out of 

 the mountainous Paradise Valley, even though the trout populations 

 remain abundant with numerous large fish down to the Stillwater 

 River confluence. The 74 miles of the Yellowstone from the 

 Boulder River to its convergence with the Clark's Fork received a 



146 



