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lower Green River do not decline significantly, (2) estimated mean recruitment of fish 400 to <br />449-mm TL (recruit-sized fish) equals or exceeds estimated mean annual adult mortality for the <br />sub-basin, and (3) each abundance estimate for the sub-basin exceeds 2,600 adults (U.S. Fish and <br />Wildlife Service 2002). <br />Our goal was to obtain accurate and precise abundance estimates for Colorado <br />pikeminnow in the Green River sub-basin. Study objectives listed in separate research proposals <br />for the middle and lower Green River abundance estimates to achieve that goal were summarized <br />as follows: <br />1. Complete three or more sampling passes through the study area to capture recruit- <br />sized and adult Colorado pikeminnow, <br />2. Obtain highest possible rates of capture of Colorado pikeminnow within <br />concentration habitats and maximize number of individuals marked on each <br />sampling occasion, <br />3. Obtain estimates of probability of capture and abundance for Colorado <br />pikeminnow in each reach and for the entire study area, <br />4. Evaluate abundance of Colorado pikeminnow in canyon reaches relative to other <br />more intensively sampled reaches, and <br />5. Design a procedure for monitoring population abundance, survival, and <br />recruitment, using data collected during the study. <br />This paper describes the first efforts to quantify abundance, survival rates, recruitment, and <br />population trends for Colorado pikeminnow in the Green River sub-basin, based on sampling <br />conducted from 2000-2003. <br />11