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previous October (x = 41.7, N = 141 upper; x = 42.5, N = 1,102 lower) in <br />five out of six cases (t-tests, P < 0.05). <br />Discussion <br />Distribution and Hatching. Drift net and seine samples in 1987 <br />indicated that larval Colorado squawfish rapidly dispersed downstream from <br />the Yampa River to the Green River. This is supported by Nesler et al. <br />(1988) who stated that young Colorado squawfish were transported <br />downstream and out of the Yampa River within 3 to 15 d after hatching, and <br />may be present in a 6 km river reach for only 1 - 2 d. We did not capture <br />larvae in the lower Yampa and upper Green rivers between June 29 and July <br />3 1987, but they were present from the Yampa River spawning site <br />downstream to RK 362 on the Green River July 13-24. Drift net catch at the <br />mouth of the Yampa River showed peak larval abundance occurred 17 July, <br />and a back-calculated age of 11 d (average TL 9.0 mm).~I~f we assume that <br />the fish hatched at the midpoint of the spawning area (RK 29) and emerged <br />5 d after hatching (Hamman 1981), the larvae drifted 29 km in <br />approximately 6 d. By mid-August, age-0 postlarvae were not captured in <br />the Yampa River, although they were taken in the Green River immediately <br />below the Yampa River. Postlarvae were not detected in the Green River for <br />80 km below the Yampa River confluence in October. <br />We do not rule out a possibility that some age-0 fish in the two <br />nursery areas could be the result of some spawning below the two known <br />spawning areas. However, evidence is convincing that long distance drift <br />occurs, and we presume that concentrations of age-0 Colorado squawfish <br />found in the Green River are the result of downstream drift from the two <br />spawning areas. This is supported by the following: Most Yampa River <br />12 <br />