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Within Old Charley Wash, spatial and temporal resource partitioning may have occurred. Although high variation was observed in capture rates, red shiners tended to be captured more frequently in deeper, open water environments. Conversely, fathead minnows and green sunfish showed little habitat preference, being collected in most habitats in equivalent numbers within gear types. Sm~ll carp tended to be captured more frequently in shallow emergent and flooded terrestrial vegetation than in deeper open water environments. Use of emergent vegetative habitats by small carp is advantageous to avoid predators and also provides access to high invertebrate/prey densities associated with macrophytes. Use of increased structural complexity would reduce encounter rates with predators (Savino and Stein 1982). In addition, high densities of small invertebrate organisms are associated with macrophytic vegetation that would provide high prey densities (Whiteside et al. 1978). If age-O razorback sucker use similar habitat, predation pressure from adult red shiners, green sunfish, and other predators would be reduced. From a temporal prospective, age-O fathead minnows, red shiners and green sunfish appeared in Old Charley Wash in late June or July, following peak numbers of zooplankton and after the appearance of larval razorback sucker. Despite the low numeric percent of juvenile razorback sucker collected in Old Charley Wash, their collection was significant because, 1) they represent the greatest number of juvenile fish ever reported in the Upper Colorado River Basin, 2) fish were collected in two successive years, and 3) fish were able to survive through the period of greatest mortality among age-O fish. Although it is likely that nonnative fishes reduced the numbers of age-O razorback sucker that survived in Old Charley Wash, without the nursery habitat provided by the floodplain wetland it is probable that no razorback sucker would have survived to the juvenile lifestage. Thus, age-O razorback sucker survival may be first limited by habitat and secondarily influenced by predation and competition. Capture of juvenile razorback sucker in successive years in Old Charley Wash suggest a pattern of wetland use by razorback sucker larvae and that fish will continue to use floodplain wetlands as nursery sites in the future if flows and access are provided. Lastly, because razorback sucker survived and grew at similar rates to carp in the wetland indicated that these fish can survive and grow in a floodplain wetland dominated by nonnative predators and competitors. In 1994, three confirmed wild yearling razorback sucker were captured by Fish and Wildlife Service personnel from L-3 pond in the Leota Bottoms complex on the Ouray National Wildlife Refuge in 1994 (Vernal CRFP, unpublished data) in the presence of nonnative fishes in depression wetlands. Because wild juveniles have been collected from multiple years from at least two large wetlands, it is possible that razorback sucker recruitment may occur in other large floodplain wetlands, despite the presence of large numbers of nonnative fishes. If it is assumed that the same production of age-O razorback sucker per acre occurred in all large depression wetlands in the Uintah Basin (according to the surface acreage listed. in Irving and Burdick 1994),362 and 582 wild, age-O razorback sucker would have been produced in the Unitah Basin in 1995 and 1996, respectively. Although the size of fish collected while draining Old Charley Wash (i.e. <125 nun) does not represent recruitment to the adult spawning population, this size of fish has passed the age of greatest mortality (Weatherly and Gill 1987) and offers a potential for recruitment heretofore considered absent. Despite successful reproduction of razorback sucker in the Lower Colorado River Basin reservoirs (Minckley et al. 1991), natural recruitment is prevented largely due to nonnative predation (Marsh and Langhorst 1988). The majority of juvenile and wild recruited adult razorback sucker that have been collected in the Lower Basin since the 1980's were found in 43