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I I I I I I I I I I I I I I I I I I I during high spring runoff so their apparent preferred habitat at that time is areas of low velocity and a sand-silt substrate (Wick et al 1982). Other times of the year they are not taken as commonly and use a variety of habitats, but still are usually caught in slow areas. They spawn in May at river temperatures of 120 to 160C. They apparently spawn over gravel bars in the river, although ripe adults have been taken from slow water areas (Wick et al 1982). Few young razorbacks have been found in the Upper Colorado Basin, indicating poor reproductive success, or the inability to catch the young. Therefore, habitat for young is not known. One potential larval razorback was collected at Parachute in 1983, about 10 miles above De Beque (Woodward- C 1 yd e 1983). Razorback reproduction was never well documented in the lower Co 1 orado River, although recruitment has been suspected, espec ia lly in riverine habitats. It appears that 1984 was an unusual year in that 1 arval razorback were found in lake Mohave, as well as riverine portions of the lower Colorado River (Johnson 1984). Flows in the lower Colorado River were at record flood levels throughout 1983 and 1984 due to 1983 and 1984 runoff. It appears that the high flows may have st imul ated reproduction of the razorback sucker. Engineering-Science (1983) conducted larval fish surveys in the Colorado River at De Beque in the sunmer of 1983. They did not find any larval razorbacks or other candidate or listed species at any of their stations. Major reasons for the decline of the razorback are those mentioned above, alteration of habitat by dams and impoundments. In the upper basin and the upper Colorado River, lack of reproduction appears to be the irrmediate problem (Wick et al 1982). Reasons for this are not - 30 -