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"In Lake Mojave, males stage over coarse, wave washed cobble in water 0.5-5 m deep. Groups of up to several hundred fish ... move slowly a meter or less from the bottom or lie immobile near or on the substrate for hours. Based on trammel netting, females remain in deeper water until ripe, then appear singly on the spawning grounds ... When she is ready to spawn, a female, flanked by two or more males, separates from a group and moves to the bottom The males press closely against the female's posterior abdomen and caudal peduncle, and all contact and agitate the substrate for three to five seconds in apparent spawning convulsions after which they typically return to a larger group... The entire sequence lasts from a few seconds to three minutes, usually the former. Females recognizable because of an injury or some other distinctive feature have been observed to spawn repeatedly in a given hour and day, and on successive days within a week." Riverine habitats. The reproductive ecology of riverine razorback suckers has been most intensively studied in the Green and Yampa rivers (McAda and Wydoski 1980, Tyus 1987, Tyus and Karp 1990, Modde and Irving 1998). Staging occurs in flooded lowlands and eddies formed in the mouths of tributary streams, and then the fish move to main-channel sand, gravel and cobble bars for egg deposition (Tyus 1987, Tyus and Karp 1990). Radiotracking and recaptures of tagged fish indicated that fish were homing to two spawning sites in Dinosaur National Monument: one in the Green River near Jensen, Utah, and one at the mouth of the Yampa River (Tyus and Karp 1990). Larval razorback suckers recently have been captured below these two areas, and in others (Muth et al 1998). Although some radiotagged fish have been monitored on more than one known or suspected spawning areas (Tyus and Karp 1990, Modde and Irving 1998), it is not known if individual fish actually spawn at more than one site, or whether fish residing in locations distant from their preferred spawning area are only moving through one spawning area in route to another (noted by Tyus and Karp 1990). 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 increasing spring flows and average water temperatures of 14°C. (range 9-17°C or 48-63°F; Tyus and Karp 1990). Thus, the time of spawning is later than that observed for the lower basin populations, but the temperature range 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 precluded by high turbidity prevalent during spring flows. 9