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Yampa and Green rivers (Vanicek et al. 1970; Holden and Stalnaker 1970, <br />1975a, 1975b). <br />This study was initiated as part of a larger program to assess <br />status and habitat needs of endangered fishes in the Yampa River. Our <br />objectives were to locate humpback chubs in DNM, and if successful, <br />identify their spawning areas, and evaluate habitat use (including flow <br />and temperature requirements) and species associations during spring and <br />early summer. We provide the first published account of a reproducing <br />population of humpback chub in the Yampa River, as evidenced by capture of <br />ripe adults and young fish. <br />Methods <br />The lower 73.6 km of the Yampa River (i.e., Yampa Canyon: Echo Park <br />to Deerlodge Park) were sampled in July 1986 and May through early July <br />1987 - 1989 (Figure 1). Whirlpool and Split Mountain canyons of the Green <br />River (km 515-550) were also sampled in late June and July 1986 and <br />several times May through July 1987 and 1988. Sampling was designed to <br />precede peak flows and follow thereafter at weekly intervals (depending on <br />river level), so to insure an accurate assessment of humpback chub <br />spawning period. Thus, sampling was not conducted during peak runoff (2-4 <br />week period depending on water year), and was terminated each summer with <br />attainment of low base-flows. Sampling was initiated late during spring <br />runoff in 1986 and therefore, 1986 was excluded from our evaluation of <br />humpback chub spawning period. <br />Riffles, small rapids, runs, eddies, pools, and backwaters were <br />sampled with electrofishing, trammel nets, and angling with baited hooks. <br />All habitat types were sampled each year, but effort was allocated in <br />4