If they were in the Poudre, its because a bucket biologist planted them in there. I doubt there are any left after 20 years. They are only native to rivers that head toward the Pacific. The one exception are a few of the upper drainages of the Missouri river.
Biologists are using electrofishing and mark-recapture methods to evaluate mountain whitefish population size in Colorado drainages where fish are native (Yampa and White Rivers), as well as where these fish were relocated in the 1940s (Cache la Poudre and Colorado Rivers). Population monitoring is essential for evaluating the health of these fisheries.
The Cache la Poudre River has been positive for M. cerebralis since the late 1980’s, and is known to harbor very high numbers of the parasite. Natural recruitment failures in rainbow trout have occurred there since the early 1990’s. Whitefish samples had not been submitted for evaluation in the past primarily due to the scarcity of the species in the standard population estimate samples. The species has never been abundant in the Cache la Poudre River, with estimates of only 175 fish (>152 mm) per mile reported by Klien (1974) in the most populated reaches from 1962 through 1973.
Pretty bony, I was using them for dog food, I used to catch those glorified suckers in the Snake river in wyoming. We need lake Whitefish in some of our big reservoirs for forage like they have in Flathead lake.