Crowsnest River Drainage Sport Fish Population Assessment 2010
The Crowsnest River is one of the most popular trout fisheries in Alberta. However, increased angling pressure, habitat degradation from recreational and industrial activities, and the invasion of less popular introduced species threaten the fishery. This study monitors populations of rainbow trout and native mountain whitefish, the two primary species in the sport fishery, using electrofishing and mark-recapture techniques.
Of 3,979 salmonid fish captured in the Crowsnest River, 65% were rainbow trout and 30% were mountain whitefish. The proportion of the mountain whitefish catch that was legal-harvest-sized, quality-sized, and above the slot size was 44%, 25% and 6%, respectively; greater than the proportion of the rainbow trout catch in these size categories at 11%, 7%, and 2%, respectively. The total tributary catch was 1,085 fish, and was dominated by Westslope cutthroat trout, rainbow trout, and their hybrids (Oncorhynchus species) at 84% combined, and respectively at 42%, 27%, and 14% of the catch. Estimated abundance of rainbow trout in the main-stem of the Crowsnest River was 80,131 fish of which 8,501 were legal-harvest-sized, 5,290 were quality-sized, and 1,445 were above the slot size. Estimated mountain whitefish abundance was 16,517 fish, with 7,340 legal-harvest-sized, 3,816 quality-sized, and 1,743 above the slot size. While the total estimated main-stem abundance was nearly five times greater for rainbow trout, the proportion of legal-harvest-sized fish, quality-sized fish, and fish above the slot size was greater for mountain whitefish. Total estimated tributary populations of Oncorhynchus trout species was 60,637 individuals, of which 34% resided
in Blairmore Creek.
Both the highest main-stem fish densities and the highest incidence of hooking damage occured between the Highway 507 and the East Hillcrest bridge crossings. Incidence of hooking damage for all rainbow trout, those of legal-harvest-size, quality-size, and above the slot size averaged 3%, 16%, 9%, and 9%, respectively; whereas mountain whitefish hooking damage averaged 3%, 3%, 3%, and 4%, respectively.
Invasive brook trout and brown trout were most abundant in the upper reaches of the main-stem river, upstream of the town of Frank, and in the tributaries of Drum Creek, Gold Creek, and Allison Creek. Bull trout were captured only in the main-stem river, downstream of Lundbreck Falls.
Westslope cutthroat trout populations were most intact in the tributaries of Island, Giardi, Star, upper Blairmore, upper Gold and upper Rock Creeks. Upstream of Lundbreck Falls, rainbow trout and mountain whitefish were the dominant species, whereas downstream of Lundbreck Falls sucker species were dominant. Small sized fish were most strongly represented in the main-stem population of rainbow trout, whereas the mountain whitefish population structure showed no trend in capture
frequency by size, with a relatively homogenous representation of fish across the full range of sizes.