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<br />~ <br />0 <br />C-~ <br />C\J 19 <br />" <br />c.. <br /> <br />Temperature also affects egg development and hatching. In the laboratory. egg <br />mortality was 100 percent in a controlled test at 130 Co At 130 to 180 C. <br />development of the egg is slightly retarded. but hatching success and survival <br />of larvae was higher. At 200 to 260 C. development and survival through the <br />larval stage was up to 59 percent (Hamman 1981). Juvenile temperature <br />preference tests showed that preferred temperatures ranged from 21.9o.to 27.60 <br />C. The most preferred temperature for juveniJes and adults was estimated to <br />be 24.60 C. Temperatures near 240 C also are needed for optimal development <br />and growth of young (Miller et al. 1982). <br /> <br />Most information on Colorado squawfish reproduction was gathered from spawning <br />sites on the lower 20 miles of the Yampa River and in Gray Canyon on the Green <br />River (Tyus et al. 1984. Tyus and McAda 1984. Tyus 1985. Wick et al. 1985. <br />Tyus 1990). Colorado squawfish spawn after the peak runoff season from June <br />to September. Spawning begins when water temperatures reaches 180 to 250 C. <br />and peak spawning activity occurs between 220 to 250 C (Haynes et al. 1984. <br />Archer et al. 1986, Tyus 1990). During the decline in water level following <br />peak runoff. spawning adult fish move into run-riffle areas and occupy run. <br />eddy. and pool habitats (Tyus 1990). After spawning. adult Colorado squawfish <br />utilized a variety of riverine habitats including eddies. backwaters. <br />shorelines, and others (Tyus 1990). <br /> <br />Specific spawning sites of Colorado squawfish have not been identified outside <br />of the Green River basin. However, spawning has been confirmed by the <br />presence of larval squawfish in two reaches of the Colorado River: Black <br />Rocks to Lorna. and Grand Junction to Clifton (McAda and Kaeding 1991). Larval <br />Colorado squawfish also have been collected both upstream and downstream of <br />Redlands Diversion Dam (Burdick 1997). The presence of larval squawfish <br />aggregations and suitable spawning habitat in the Colorado River near Cataract <br />Canyon, Professor Valley. and upstream from the Dolores River confluence <br />indicate spawning is occurring in or near these areas as well (Archer et al. <br />1986. Valdez 1990). <br /> <br />Data indicate that clean cobble substrates are necessary for spawning and <br />incubation (Tyus and Karp 1989). Substrates are swept clean of finer <br />sediments by high flows scouring the bed prior to the spawning period. <br />O'Brien (1984) studied the hydraulic and sediment transport dynamics of the <br />cobble bar within the Yampa River spawning site and duplicated some of its <br />characteristics in a laboratory flume study. Based on field observations. he <br />reported: <br /> <br />"On the rising limb of the hydrograph. sands are deposited in the <br />cobble interstices. These sands are interchanged between the bed and <br />