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<br />habitat, The use of spring backwaters by adult Colorado <br />squawfish prior to spawning migration or spawning has been <br />observed in both the Yampa and colorado rivers (Nesler 1989, <br />1990,) The significant use of complex river channels by adult <br />Colorado squawfish over simple mainchannel habitat has been <br />documented in the Colorado River by USFWS in Grand Junction, <br />Colorado (Osmundson and Kaeding 1990), The use of summer <br />backwater nursery habitat for young-of-the-year Colorado <br />squawfish has been widely documented in the Green River (Tyus <br />et al. 1982, Haynes et aI, 1984, Tyus and Haines, in press), <br />fall-winter baseflow conditions in low flow years may resuit <br />in pools connected by shallow riffles that mayor may not b e <br />passable for adult fish. Pool and run habitat were often used <br />by adult Coloradosquawfish overwinter (~aldez and Masslich <br />1989, Wick and Hawkins 1989,). The presence and amount. of <br />pool and deep run habitat in the fall would indicate if this <br />habitat might be limiting. <br />A second part of the physical habitat assessment would be <br />the location of suitable spawning sites within the target <br />reaches, An hypothesis regarding historic Colorado squawfish <br />spawning ecology in the upper mainstem colorado River is that <br />the instream barriers located on the colorado River are <br />between adult fish and their spawning areas, or are between <br />historic adult habitat and spawning habitat located upstream <br />and nursery habitat downstream in the Grand Valley. As stated <br />in the. FWS Work Plan, "the reintroduction site would. be <br />carefully chosen for its adequacy as a future spawning and <br />rearing area...". It is suspected that suitable spawning <br />sites may be found in Debeque Canyon above the influence of <br />Highline Diversion Dam. For this study it would also be <br />necessary to evaluate the influence of the diversion structure <br />upon the reintroduced population and it spawning success. <br />Flow regime within the target reach will be monitored <br />using USGS gage records at Glenwood Springs (09085100), <br />Debeque (09093700), and Cameo (09095500), and Stateline <br />(09163500) . Temperature regime will be monitored in the <br />target reach using instream thermographs to complement USGS <br />data collected at Cameo, Each thermograph will be located <br />upstream of the USGS gage station. Flow and temperature <br />regime data collected in the historic, unoccupied reach will <br />be compared to similar information in the Yampa, Green and <br />mainstem Colorado rivers, <br />The reach will be surveyed annually by boat at <br />three different flow levels to determine number and area <br />of the physical habitat types listed, <br />Potential spawning habitat in current unoccupied reaches <br />will be determined from descriptions of known spawning areas <br />in the Yampa and Green rivers and comparison with similar <br />attributes sampled on site (e,g, in Debeque Canyon), Mapping <br />of potential spawning sites for flow and habitat types will be <br />conducted during the suspected spawning period and examination <br />of substrate type suitability will occur during exposure of <br /> <br />3 <br />