2004-06-29_PERMIT FILE - C1981038 (3)

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Bioloov The life-histon• phases that appear to be most critical for the Colorado pikeminnow include spawning, egg fertilization, and development of larvae through the first year of life. These phases of Colorado pikeminno~v development aze tied closely to specific habitat requirements. Natural spawning of Colorado pikeminnow is initiated on Lhe descending limb of the annual hydrosraph as water temperatures approach 20° C. Spawning, both in the hatchery and in the field, generally occurs in a 2-month timeframe between July 1 and September 1, although high flow water yeazs may suppress river temperatures and extend spawning in the natural system into September. Conversely, during low flow yeazs when the water warms eazlier, spawning may occur in late June. Temperature also has an effect on egg development and hatching. In the laboratory, egg mortality was 100 percent in a controlled test at 13° C. At 16° C to 18° C, development of the egg is slightly retarded, but hatching success and survival of larvae was higher. At 20° C to 26° C, development and survival through the larval stage was up to 59 percent (Hamman 1981). Juvenile temperature preference tests showed that preferred temperatures ranged from 21.9° C to 27.6° C. The most preferred temperature for juveniles and adults was estimated to be 24.6° C. • Temperatures neaz 24° C aze also needed for optimal development and growth of young (Miller et al. 1982). Most information on Colorado pikeminnow reproduction was gathered from spawning sites on the lower 20 miles of the Yampa River and in Gray Canyon on the Green River (Tyus et al. 1982; Tyus and McAda 1984; Tyus 1985; Wick et al 1985; Tyus 1990). Colorado pikeminnow spawn after the peak runoff season from June to mid-August. Spawning begins when water temperatures reaches 18° to 2S° C, and peak spawning activity occurs between 22° to 2S° C (Haynes et al. 1984; Archer et al. 1985; Tyus 1990). During the decline in water level following peak runoff, spawning adult fish move into run-riffle aeeas and occupyrun, eddy, and pool habitats (Tyus 1990). Afrer spawning, adult Colorado pikenunnow utilized a variety of riverine habitats including eddies, backwaters, shorelines, and others (Tyus 1990). Specific spawning sites of Colorado pikeminnow have not been identified outside of the Green River Basin. However, spawning has been confirmed by the presence of larval pikeminnow in two reaches of the Colorado River; Black Rocks to Loma, and Grand Junction to Clifton (McAda and Kaeding 1991). The presence of larval pikeminnow aggregations and suitable spawning habitat in the Colorado River neaz Cataract Canyon, Professor Valley, and upstream from the Dolores River confluence indicate spawning is occurring in or neaz these areas as well (Archer et al. 1985; Valdez 1990). Data indicates that clean cobble substrates aze necessary for spawning and incubation (Tyus and Karp 1989). Several studies on the cobble cleaning process have been conducted at a knowtt spawning location in Yampa Canyon. O'Brien (1984) studied the hyd:-aulic and sediment transport dynamics of the cobble baz within the Yampa River spawning site and duplicated some