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as would additional sampling passes. Thus the humpback chub population in Yampa Canyon seems to be between 100 and 2000 adults and our best estimate is about 400 fish> 150 mm TL. An estimate with reliable confidence will be difficult to obtain without extraordinary effort. Population status. The Yampa Canyon humpback chub population appears to be persistent, successfully recruiting, but sparsely distributed, consisting of only a few hundred to a few thousand adults. Tyus (1998) stated that the Yampa River population may have declined over the past 50 years, citing the apparent reduction in range in the Castle Rock area and the proliferation of channel catfish since the mid-1940s, but little supporting information on chub densities is available. The 1987-1989 Colorado River Fish Project survey (Karp and Tyus 1990) showed angler catch of 0.65 fish per h and electro fishing catch of 1.03 fish per h compared with the current study of angling catch of 0.04 fish per h and electrofishing catch of 0.8 fish per h. But, as pointed out above, we are hesitant to draw conclusions about the population trend by comparing the catch rates of these two studies. The size distribution in the lower portion of the river consisted of both adult and juvenile fish indicating some level of recruitment. Proposed monitoring. An efficient monitoring plan is a critical part of any recovery program. It provides feedback on the change of status of the population for possible downlisting or for need of further protection, and it provides information on population response to management activities, like non-native fish control. However, an intensive capture-recapture study that results in a precise population estimate for humpback chub is not feasible for Yampa Canyon, without extraordinary effort, primarily because of low probability of capture. Similarly, 15