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control measures must be implemented through concurrent experiments by application of adaptive management (Walters 1986; Walters and Hillborn 1978). Caotive Prooaaation may be the Only Short-Term Solution. The razorback sucker was considered the highest priority for propagation among the four endangered Colorado River fishes (Wydoski 1994) because the stocks are declining and little or no recruitment has been documented for this species in the Upper Colorado River Basin. The Recovery Program Biology Committee agreed that augmentation stocking was required in the middle Green River to increase and stabilize the present population (Wydoski 1994) that is estimated to be 500 razorback suckers (Modde et al. 1995). A dramatic decline in razorback suckers occurred between 1974 and 1991 in river miles 152.8-185.1 of the Upper Colorado River (Burdick 1992). A high capture of 206 razorback suckers in this reach during 1974 declined until no fish were captured during 1989-1992. Three adult razorback suckers were captured in this reach in 1993 and one in 1995. The Recovery Program Bi 01 ogy Committee agreed that restoration stocki ng of the razorback sucker was a high priority. The bony tail is nearly extirpated from the upper basin. Only occasional specimens are captured at infrequent intervals with great distances between captures. Therefore, captive propagation will be an important fishery management tool in augmentation and restoration stocking of razorback sucker and bony tail in the Upper Colorado River Basin. Human intervention may be required to maintain razorback suckers in the Upper Colorado River Basin by rearing the fish in predator-free off-channel habitats similar to the approach being used in Lake Mohave (Minckley et al. 1991; Mueller 1995). Razorback suckers could be reared in predator-free off-channel habitats such as oxbow lakes or wetland habitats in floodplain depressions to a size that predation by nonnative fishes would be considerably reduced. Large blue heron (Ardea herodias) rookeries in floodplain habitats of the upper basin. While blue herons are not expected to feed on larval razorback suckers, they are effective predators on juvenile fishes in shallow water. About one-half meter of water would preclude predation by blue herons since they are only effective piscivores in shallower waters (Table 3). Although reari ng razorback suckers in predator-free off-channel habitats does not const itute recovery since the popul at ions woul d be ma i nta i ned through human i ntervent ion, it woul d be a vi abl e pract ice to prevent ext i nct ion unt il sol ut ions for recovery are determined. The genetic integrity of endangered fish stocks in the Upper Colorado River Bas in wi 11 be ma i nta i ned by app 1 yi ng sound genet i c guidelines (Williamson and Wydoski 1994) to prevent irreversible losses of genet i c di vers ity that may result from management i ntervent ions or 1 ack of action. XIV. IMPORTANT BOTTOMLAND HABITATS IN THE UPPER COLORADO RIVER BASIN Bottomland habitat sites (135 sites in the Green River Subbasin [Green River - 132 sites; potential area of 18,430 acres or 7,458 hectares, Yampa River - 1 site; potential area of 21 acres or 8.9 hectares, and White River - 2 sites; potential area of 634 acres or 256 hectares] and 158 sites in the Colorado River Subbasin [Colorado River - 110 sites; potential area of 12,222 acres or 4,948 hectares] and Gunnison River - 48 sites; potential area of 3,223 acres or 1,305 hectares) that could provide nursery areas for recovery of the razorback sucker 16