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. . . Acetone-dried CP has been used in all efforts to procure eggs of bonytail chub (Hamman 1982a, 1985b, Jensen 1983a). The injection rate was 4 mgjkg of body weight, and ovulation occurred in 18 - 20 hours (Table 2.5a). Wild bonytail chub produced greater numbers of eggs per female than domestic fish, perhaps because of age and fish size. Hamman (1982a) reported 25,090 eggs per female from 6 wild Lake Mohave fish, while Hamman (1985b) reported only 4,990 and 16,464 eggs per female for 2 and 3-year old fish, respectively. Similarly, Jensen (1983a) reported an average of 4,677 eggs per female for 2-year old hatchery fish. The lower fecundity of hatchery fish may be caused by the relatively young age (2 and 3-year old fish) and smaller size of the hatchery fish. Ninety percent of eggs hatched from wild Lake Mohave bonytail chubs that were incubated at 20 -210C, while 55% hatched at 16 - 1rC, and only 4% hatched at 12 - 130C (Hamman 1982a). Hatching times at these temperatures were 99 - 174 hours, 170 - 269 hours, and 334 - 498 hours, respectively (Table 2.5b). Hamman (1985b) also found that only 17.1 % of eggs hatched from 2-year old hatchery reared fish and 37.7% hatched from 3-year old fish, while Jensen (1983a) reported 67.5% hatching success of eggs from 2-year old domestic fish. Bonytail fry (Phase I) were held in lightly fertilized circulating troughs, while fed on natural zooplankton for 21 days, followed by a commercial trout starter (Table 2.5d). The size of these fish was 18.1 mm in 28 days and 49.5 mm in 70 days, with a survival rate of 71 % in 70 days (Hamman 1982a). Razorback Sucker The first recorded efforts at culturing razorback suckers were by Inslee (1981, 1982) at Dexter NFH. A summary of past culture efforts for razorback sucker is presented in Table 2.6. Using wild fish from Lake Mohave, Arizona, he injected females intraperitoneally with HCG (50 and 100 Lu.jlb) and CP (2 mgjlb) to accelerate timely maturation of eggs (Table 2.6a). The fish produced eggs in several days with samples of 130 eggs per gm and 233 fry per mI. Jensen (1983b) also injected female razorback suckers with 100 Lu. HCG per lb at 24-hour intervals with successful ovulation in several days. He also found that males could be injected once with 300 Lu. HCG per lb to insure a viable and timely production of milt. Hamman (1985b) used HCG at a rate of 220 Lu. per kg at 24-hour intervals, and reported successful ovulation after several days. 2.2 - 5