Rock Creek is located 25-east of Missoula, Montana off Interstate 90. Rock Creek headwaters originate from three-Mountain Ranges. The North Fork of Rock Creek and the West Fork of Rock Creek originate from the Sapphire Mountain Range. The East Fork of Rock Creek and the Middle Fork of Rock Creek originate from the Anaconda Mountain Range and the Anaconda – Pintler Wilderness Area. The Upper Willow Creek originates from the John Long Mountains. There are numerous small streams flowing into Rock Creek on its journey north to its confluence with the Clarkfork of the Columbia River. In the 1980’s Rock Creek contained roughly 2,000 Rainbow Trout per mile of stream in the lower 28-miles of Rock Creek; from Gillies Bridge downstream to the mouth of Rock Creek. In the 1990’s the Rainbow Trout population in Rock Creek plummeted to just 300 Rainbow Trout per mile of stream. This drastic decline in the Rainbow Trout population was caused by Whirling Disease and by the Montana Department of Fish, Wildlife and Parks decision to halt the stocking of Hatchery Rainbow Trout into the East Fork of Rock Creek Reservoir. To this day there has been no significant increase in the Rock Creek Rainbow Trout population. However, the Native Westslope Cutthroat Trout population in Rock Creek has rebounded somewhat to fill the void of lost Rainbow Trout population. Also the non-native Brown Trout population is on the increase. The Rock Creek fishery consists of native Westslope Cutthroat Trout up to 24-inches in length, native Bull Trout up to 36-inches in length, native Mountain Whitefish up to 24-inches in length, non-native Brown Trout up to 26-inches in length, non-native Rainbow Trout up to 24-inches in length and non-native Brook Trout up to 14-inches in length. Important Entomology And Forage Fish on Rock Creek are: Stone Flies: 1. Skwala (Skwala parallela) March – April (Size 8-10-12-14) 2. Salmon Fly (Pteronarcys californica) May – July (Size 2-4-6-8) 3. Western Big Golden Stone (Calineuria californica) May – August (Size 4-6-8-10-12) 4. Western Medium Golden Brown Stone (Isoperla sp.) June – September (Size 4-6-8-10) 5. Little Yellow Stone (Alloperla pallidula) June – October (Size 12-14-16-18) 6. Little Olive Stone (Alloperla delicata) May – August (Size 12-14-16-18) 7. Winter Stone (Capina sp.) January – March (Size 14-16-18) May Flies: 1. Western Black Quill (Rhithrogenahageni) March – April (Size 12-14) 2. Early Blue-Winged Olive (Baetis tricaudatus) March – April (Size 14-16-18) 3. Late Blue-Winged Olive (Baetis parvus) June – November (Size 16-22) 4. Little Western Blue-Winged Olive (Ephemerella margarita) July – September (Size 16-22) 5. Western Green Drake (Drunella grandis) June – July (Size 10-12) 6. Pale Morning Dun (Ephemerella inermis and Ephemerella infrequens) May –September (Size 14-16-18) 7. Small Western Green Drake (Ephemerella flavilinea) June – August (Size 14-16) 8. Western Leadwing (Isonychia sicca) June – July Size (Size 10-12) 9. Dark Gray Quill (Ameletus connectus) May – June (Size 12-14) 10. White Winged Black (Tricorythodes minutus) July – October (Size 18-20) 11. Midges (Diptera / Chironomous) Caddis Flies 1. Grannom (Brachycentrus occidentalis) April – May (Size 12-14-16) 2. Green Sedge (Ryacophila sp.) April – October (Size 10-12-14-16) 3. Great Gray Spotted Sedge (Arctopsyche grandis) May – August (Size 8-10-12) 4. Little Tan Short Horn Sedge (Glossosoma sp.) June – August (Size 14-16-18) 5. Spotted Sedge (Hydropsyche sp.) July – October (Size 12-14-16) 6. Little Plain Brown Sedge (Lepidostoma pluviale) June – August (Size 14-16-18) 7. Giant Orange Sedge (Dicosmoecus sp.) September – October (Size 6-8-10-12) 8. Spruce Bud Worm Moth July – August (Size 10-12-14) Forage Fish 1. Mottled Sculpin (Cottus bairdi) Year Round (Size 3/0-2/0-1/0-2-4-6-8) 2. Slimy Sculpin (Cottus cognatus) Year Round (Size 3/0-2/0-1/0-2-4-6-8) 3. Black-Nose Dace (Rhinichthys cataractae) Year Round (Size 3/0-2/0-1/0-2-4-6-8)