Currently, the lower quarter mile of Crawford Creek, downstream from an old water diversion structure, supports mixed populations of rainbow trout (Oncorhynchus mykiss), westslope cutthroat trout, rainbow trout x westslope cutthroat trout hybrids, and brook trout (Salvelinus fontinalis). The next two miles (upstream) of the creek supports rainbow x westslope cutthroat trout hybrids and a few brook trout. The uppermost reaches of Crawford Creek (approximately 0.5 miles), above a natural waterfall barrier, supports a small population of genetically pure native westslope cutthroat trout. A new permanent barrier to upstream fish migration was constructed near the downstream end of Crawford Creek in 2005. The proposed action involves removing non-native fishes from the 1.5 miles of stream between the natural upstream barrier and the recently constructed downstream barrier using piscicides. Crawford Creek will then naturally be re-colonized by genetically pure WCT drifting in from upstream areas.