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mainstem river are teeming with catfish, carp, black bass, striped bass, sunfish and other non-native fishes. Implications of these introductions are difficult to quantify; however, predation is considered the single most important factor limiting recruitment in Lake Mohave (Minckley 1983; Marsh and Langhorst 1988; Minckley et al. 1991). Figure 1. The razorback sucker (Xyraucltell texallus) is endemic to the Colorado River of the southwestern region of the United States. Efforts to restore the razorback sucker and other native fish began in the late 1960's and since then, there have been three different restoration approaches within the river basin. Between 1980 and 1990, a massive stocking effort attempted to reintroduce razorback suckers to historic habitat in Arizona, without improving habitat conditions. A IS-year program began in 1988 to recover the endangered fish in the upper portions of the Colorado River Basin, where conditions were believed to be more pristine. Activities have focussed on improving habitat conditions, while minimizing stocking augmentation. It's believed that fish populations should expand on their own accord as a result of habitat improvements. The last major program being attempted is in the lower basin where environmental impacts are the most severe, and recovery, or the development of self-sustaining populations, is unlikely. Here, resource managers are maintaining populations of razorback suckers by capturing and rearing wi Id sucker larvae to a size large enough to insure their survival. The continued presence of razorbacks in highly modified habitats will depend upon continued maintenance and integration into long-term management plans. This paper discusses those projects and focusses on the Lake Mohave program. RESTORA nON EFFORTS Restoration efforts have evolved along with our understanding and acknov..ledgment of the complexity of the river's ecosystem. The management philosophy during the 1970's, 1980's, and early 1990's was primarily based on the assumption that restoration might be possible \vith a simple physical fix. The physical changes have been the most obvious. Efforts continue to minimize the impacts caused by fluctuating hydroelectric power generation and to operate regulatory reservoirs in a manner that more closely mimics historic seasonal flows. Levee systems and other flood protection features are being reevaluated, taking into account the loss and importance of historic