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INTRODUCTION <br />Colorado pikeminnow (Ptychocheilus lucius) is a large piscivorus cyprinid endemic to <br />the Colorado River basin (Minckley 1973). The species was once widespread in the large <br />rivers of the Colorado River Basin, but it was eliminated from rivers downstream of Lake <br />Powell by the late 1960s (Minckley 1973). Although Colorado pikeminnow still exists in the <br />large rivers of the upper basin (Tyus 1991), its range has been reduced by construction of <br />large reservoirs that eliminated habitat and changed downstream water quality (e.g., Vanicek <br />et al. 1970), and construction of instream barriers that blocked access to historic range <br />(Burdick and Kaeding 1990). In addition, more than 40 exotic species have been introduced <br />to the rivers of the upper basin (Tyus et al. 1982a); many of these species are competitors with <br />or predators on native fishes (Hawkins and Nesler 1991). Loss of habitat in the lower basin, <br />unknown status of the species in the upper basin, and potential for further habitat loss through <br />construction of more reservoirs prompted Colorado pikeminnow to be included as endangered <br />when the first list of endangered species was published in 1967 (USFWS 1967). <br />Conflicts between water development in the upper basin and endangered fish began <br />soon after the Endangered Species Act (as amended) was passed in 1973 (Wydoski and <br />Hamill 1991). In an attempt to resolve those conflicts, the Recovery Program for the <br />Endangered Fishes of the Upper Colorado River (Recovery Program) was developed to fund <br />management actions to recover Colorado pikeminnow (and other listed fishes) and allow the <br />states of the upper basin to continue to develop water (Wydoski and Hamill 1991). During <br />formation of the Recovery Program, an Interagency Standardized Monitoring Program <br />(ISMP) was developed to monitor trends in the subadult and adult Colorado pikeminnow <br />(hereinafter maturity is not referenced) population in the upper basin (USFWS 1987; McAda <br />et al. 1994). The ISMP began in 1986 and used shoreline electrofishing to develop annual <br />catch-per-effort (CPE) indices that could track changes in relative abundance of Colorado <br />pikeminnow in these reaches. Participants recognized that large changes in CPE were <br />required to detect significant differences among years (McAda 1989a,b}, but felt that trend <br />data provided useful information to managers. <br />During development of quantifiable recovery goals for Colorado pikeminnow (USFWS <br />2002), the Recovery Program recognized that the sampling effort expended in ISMP was not <br />sufficient to develop robust population estimates for the species. As a result, a more intensive <br />program was initiated that was specifically directed at developing population estimates of <br />Colorado pikeminnow for each river in the upper basin. The revised sampling protocol called <br />for sampling all of the known range of Colorado pikeminnow three times each year to develop <br />mark-recapture population estimates. Because of the expanded effort, ISMP sampling for <br />adult Colorado pikeminnow was terminated. This report summarizes the results of the <br />shoreline electrofishing portion of ISMP for 1986 through 2000. <br />