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ISMP backwater sampling evaluation <br />Colorado pikeminnow portion of ISMP employs seining in autumn to sample fishes in a subset <br />of the backwaters present in four main Upper Colorado River reaches, including one in the <br />Colorado River in the Grand Valley. The main goal of that sampling was to "provide an annual <br />index of the relative reproductive success of Colorado pikeminnow and survival of the young <br />fish through their first growing season" (McAda et al. 1994). Abundance data for fishes other <br />than the target endangered ones were also gathered. However, it was unknown if the ISMP <br />protocol was capable of detecting the presence and estimating abundance and size-structure of <br />centrarchids with the accuracy and precision needed to monitor trends in fish escapement from <br />floodplain ponds. This was especially true given that ISMP seine sampling was more suited to <br />capture open-water cyprinids than cover-dwelling centrarchids (Larimore 1961, Dauble and Grey <br />1980, Bayley et al. 1989). Therefore, the goal of this study was to quantify the bias of the <br />relatively low effort ISMP sampling to detect the presence and estimate the abundance of fishes <br />in backwaters. This study had a collateral benefit because we quantified the abundance of select <br />non-native fishes and removed large numbers of them from the Colorado River. Reducing the <br />negative effects of non-native fishes by removing them from backwaters is a goal of the <br />Recovery Program for Endangered Fishes in the Upper Colorado River Basin (Tyus and <br />Saunders 2000). Data gathered in this study was also used to examine the efficacy of mechanical <br />removal as a tool to control non-native fishes in backwaters. <br />-2-