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53 8.) Agencies should seek to establish regulatory review procedures regarding stocking of private waters and baitfish commerce to prevent undesirable introductions of nonnative fish species. 9) Endangered fish that are stocked should be large enough to avoid predation by most fishes. Minimum size should be determined by existing predator conditions and sizes. Predator free grow-out ponds should be used to obtain fish of suitable size. 10) Establish river reaches or entire rivers as natural preserves. Attempt to maintain these as refugia by providing historic flows and if possible exclusion of exotic fishes. Implementation strategy One of the objectives of this issue paper was to provide the Recovery Implementation Program (RIP) with guidance on how to approach the issue of nonnative fish impacts upon the recovery of endangered native fishes. A primary result indicated that documented evidence was severely lacking on the impacts and control of nonnative fishes. Given the 15 yr time frame set for the RIP, we are faced with two alternatives to proceed: 1) Accept the conceptual understanding that negative impacts of introduced fishes in the Colorado River Basin are significant without scientific documentation and proceed to negatively manage populations of introduced fish species perceived to be most harmful to the native fish fauna, or ' 2) Target research on introduced fish species perceived to be harmful and identify which life stages and in which habitats introduced species negatively affect endangered fishes; then manage toward reducing or eliminating the negative effect. The choices, however, are not as simple as selecting (1) or (2). Inherent within both alternatives is a subsequent decision as to whether management alternatives and field techniques exist, or can be developed, to reduce or eliminate the negative interaction. Most of the introduced fishes exist in the Colorado River Basin due to some human-related activity. Some of the nonnative species represent popular gamefish species; some represent selected species for management of forage bases for sport fisheries or common commercial bait products. In conjunction with conservation of the wildlife resource, an important mandate for state wildlife agencies is to provide public fishing recreation. Similar to water and land management activities, correction of perceived negative impacts from introduced fishes will undoubtedly restrict or eliminate certain human activities and choices, and will require documentation in order to proceed. Recommendations provided here comprise a strategy for approaching the issue of introduced fish impacts. Recommendations 1-6 for research attempt to direct this activity toward areas of major concern in a logical sequence. These activities start to answer