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December 1990 Tyus and Karp-Spawning and movements of Xyrauchen texanus 429 FIG. I-Map of study area, Green River basin. Ripe razorback suckers were usually captured in runs associated with submerged bars of cobble, gravel, and sand substrates. The average depth of these bars was 0.63 m (n = 118, SD = 0.15) and average water velocity 0.74 mls (n = 40, SD = 0.21). Although spawning behavior was not observed due to high water turbidity, the simul- taneous capture of ripe males and females indi- cated that razorback suckers were using certain riffles for spawning. Based on repeated captures over the 3 year period, locations specifically iden- tified as spawning microhabitat for razorback suckers included: Yampa River, left channel at mouth (km 0.8) and left shoreline just above Echo Park Campground (km 0.16); and Green River, right shoreline and channel below Green River Campground (km 491.2 to 500.8; directions refer to downstream orientation). Three ripe razorback suckers were also cap- tured in quiet-water habitats associated with his- torically-flooded lowlands in the Ouray area (Old Charley Wash) and flooded mouths of tributary streams (e.g., Ashley Creek and Duchesne River, 2% of all breeding captures; Fig. 1). These areas were typically low-velocity habitats of sand-silt and vegetated substrate. Razorback suckers spawned during increasing and highest spring flows as indicated by capture of ripe fish from mid-to-Iate April through May (Table 1, Fig. 2). Water temperatures were vari- able during this period but averaged about 140C (Yampa site; X = 13.80C, range of 10.5 to 160C; Jensen site; X = 14.10C, range of 9 to 170C). Ripe females were captured over an average of 27 days (range of 24 to 28 days) and ripe males over 34 days (range of 26 to 41 days; Table 1, 1987 to 1989). Some recaptured male razorback suckers (n = 25) were collected "running ripe" (sex products issuing with little or no manual pressure) for 2 to 28 days, but four recaptures of TABLE 1-Numbers of captures and capture dates of razorback suckers in the Green River basin, 1981 to 1989. N = total number of captures, n = number of ripe or tuberculate but unripe captures, numbers in parentheses indicate the number of recaptures. Ripe females Ripe males Tuberculate fish2 Year' N n Date n Date n Date 1981 73 2 (1) 6-14 May 3 (0) 6-7 May 1982 36 1 (0) 19 May 1 (0) 19 May 1983 3 2 (0) 20 Apr 1984 100 11 (1) 3 May-14 Jun 16 (2) 3 May-13 Jun 28 (9) 3 May-21 Jun 1985 18 1986 70 10 (3) 29 Apr-28 May 21 (11) 22 Apr-5 Jun 12 (3) 13 May-18 Jun 1987 64 18 (7) 20 Apr-13 May 29 (9) 20 Apr-15 May 2 (0) 7-15 May 1988 64 10 (5) 4-31 May 47 (24) 27 Apr-31 May 3 (2) 16-25 May 1989 102 22 (5) 28 Apr-25 May 68 (36) 20 Apr-30 May 1 (0) 18 May Total 530 74 (22) 185 (82) 48 (14) 'Fish captures 1981 to 1984,1985, and 1986 from Tyus, 1987. 2 Presence of breeding tubercles but no expression of sex products.