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ACKNOWLEDGEMENTS This project was funded through the U.S. Fish and Wildlife Service under Section 6 authorization of the Endangered Species Act We thank the many colleagues who contributed to the literature review and participated in the expert opinion questionnaire. Reviews from J. Bennett, K. Bestgen, B. Haines, P. Martinez, C. McAda, R. Muth, D. Osmundson, R. Valdez, E. Wick, and D. Young improved an earlier draft of this report. J. Reeve assisted in questionnaire mailing and report preparation. PREFACE Potential impacts of introduced fishes on endangered and other native fishes in the Upper Colorado River Basin (upper basin) are major concerns of the Biology Committee within the Recovery Implementation Program for Colorado River Endangered Fishes. This committee solicited development of an issue paper to provide necessary guidance for research and management of problems posed by introduced fishes. This report addresses this need. Study objectives were to: 1) assess known or suspected negative impacts of nonnative fishes on the four endangered or threatened fishes, 2) determine avenues of research necessary to provide needed data, and 3) determine management options available to minimize negative impacts and develop an overall strategy for implementation of related recovery efforts. This paper consists of three parts: a literature review, a summary of expert opinion through a questionnaire, and a synthesis with recommendations. Recommendations for research and management strategies for introduced fishes were derived from the literature review and researcher questionnaire. The terms exotic, introrJ.uced, and nonnative are often used interchangeably when describing a species not histori~lly found in a drainage. The American Fisheries Society (APS), Exotic Fishes Section (now called Introduced Fishes Section) adopted definitions in 1983 that categorized nonnative fishes by political boundaries of their origin (Shafland and Lewis 1984). An introduced or nonnative species is a broad category for any animal that occurs in a location due to man's actions. An exotic species is "an organism introduced from a foreign country (i.e., one whose entire native range is outside the country where found)lI. A transplanted species is lIan organism moved outside its native range, but within a country where it occurs naturally (i.e., one whose native range includes at least a portion of the country where found)". The AFS terminology is followed in this paper. The terms introduced or nonnative are used over the commonly, although often incorrectly, used term exotic. Papers cited may have used the term exotic in reference to introduced species, but, except within direct quotes, the correct terminology is used VI