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In. the Green River in Dinosaur National Monument, Vanicek and Kramer (1969) found that young bonytail and roundtaii chubs primarily ate chironomid larvae and mayfly nymphs. Small fish became more dependent on floating food items as they grew larger. Larger juvenile chubs ate a more diversified diet, including terrestrial and aquatic insects. During the summer, adult bonytail fed on terrestrial insects that probably were taken from the surface. No fish remains were found in bonytail stomachs. In the Gila River, Kirsch (1888) reported that food of the bonytail consisted . "almost entirely of gastropods and caddis-worms, which they crush with their powerful pharyngeals." Reservoir Life history data on bonytail in reservoirs have been collected by a number of biologists and summarized by Minckley (1985). Three specimens from Lake Mohave were estimated to be between 34 to 49 years old based on otolith examination (Minckley 1985). Bonytail in Lake Mohave generally occupy lacustrine habitat rather than upstream riverine habitat near Hoover Dam. W.L. Minckley (Arizona State University, pers. comm.) believes the cold hypolimnetic water from Lake Mead precludes use of the riverine habitat in Lake Mohave by bonytail. Wagner (1955) reported that the species was the most common one collected in gill nets and was usually found in areas over a clean, sandy bottom with reverse eddy current. The diet of bonytail chub in reservoirs appears to be primarily plankton and algae, although extensive food habit studies have not been carried out (Minckley 1973). Stomach analysis of specimens collected from Lake Mohave indicated they had preyed upon recently stocked rainbow trout fry less than 2.5 inches TL in size (Wagner 1955). Spawning behavior of bonytail was observed in Lake Mohave (Jonez and Sumner 1954), but no young have been reported. Shortly after impoundment of Lake Mohave, approximately 500 bonytail congregated over a gravel bar in water up to 30 feet deep. Generally, females were escorted by three to five males and fertilized eggs were apparently deposited randomly. No effort to guard the spawning areas by either sex was observed (Jonez and Sumner 1954). Based on egg development, Wagner (1955) concluded spawning began in late spring or very early summer. Hatche The majority of the collecting efforts in Lake Mohave since 1974 have been carved out to obtain bonytail for culture purposes, producing a total of 24 fish (Minckley 1985). Six female and five male bonytail obtained from Lake Mohave were spawned in water temperatures of 68°F at Willow Beach National Fish Hatchery (Willow Beach, Arizona), in 1981. Most eggs (90 percent) hatched 99 to 174 hours later. Only 55 percent of eggs placed in 60° to 63°F hatched between 170-269 hours) and 4 percent hatched at 54° to 55°F (between 334 and 498 hours) (Hamman 1982a). Marsh (1985) incubated bonytail eggs at 9°F intervals between 41 °F and 86°F. The hatching success was 35 percent at 59°F, 32 percent at 68°F, and 0.5 percent at 77°F; no eggs survived at 41 °F, 50°F or 86°F. Mean 35