7990 - Laserfiche WebLink

Home Browse Search

Ripe razorback suckers were captured in suspected spawning areas in the Green River from mid to late April through May (Tyus 1987, Tyus and Karp 1990). In the Grand Valley, near Grand Junction, Colorado, 40 of 42 running ripe adults were captured between May 24 and June 17 (Osmundson and Kaeding 1990). Spawning movements and the appearance of ripe fish were associated with increasin s rin flows and 9 P g average water temperatures of 14°C. (range 9-17°C or 46-63°F; Tyus and Karp 1990). Thus, the time of spawning is later than that observed for the lower basin populations, but the tem nature ran pe ge is very similar. Tyus (1987) and Tyus and Karp (1990) collected ripe adults over coarse sand substrates and in the vicinity of gravel or cobble bars submersed by an average depth of water of 0.63 m. Average velocity of water over the bars was 0.74 m/s. Direct observation of spawning behavior and gametic release was preluded by high turbidity prevalent during spring flows. Razorback sucker spawning also has been observed in riverine sections of the Colorado River below Hoover Dam (Minckley 1983). Mueller (1989) gave the following akxount of reproductive behavior in that riverine habitat: ' "Spawning behavior was similar to that reported for populations in reservoirs. However, spawning appeared to be less mobile in the river. The ' majority of fish, which appeared to be "small" (approximately 40 cm total length) males, maintained stationary positions on the downstream end of the site. This behavior was different from the roving nature previously observed and reported for reservoir-spawning groups (Minckley, 1983). Larger fish, presumably females, periodically moved into the area from the adjacent river, attracting some of the otherwise stationary males to form spawning groups of three to eight fish. These groups, composed of one female and 14 ,