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56 JOURNAL OF APPLIED AQUACULTURE A concern about population declines and lack of recruitment in ex- tant stocks (Lanigan and Tyus 1989; Marsh and Minckley 1989) has resulted in increased efforts to evaluate culture techniques to propa- gate this species. Although razorback sucker fry can be raised in ponds (Hamman 1987), their specific dietary requirements are un- known, and information about intensive culture on dry, formulated foods is scant. Maintenance of separate genetic stocks of endangered fishes re- quires raising separate lots of fish to a size large enough to bear permanent marks or tags. A lack of young (Lanigan and Tyus 1989; Marsh and Minckley 1989) and scarcity of mature fish in the wild have necessitated the development of hatchery techniques to pro- duce fry (Lanigan and Tyus 1988). In a previous study (Tyus and Severson 1990), razorback sucker fry were cultured for 45 days, utilizing commercial feeds as first exogenous foods~ However, dif- ferences in fish response to five diets indicated that a combination of diets may be required to obtain good growth and survival, espe- cially for larger fish. The objective of this study was to determine a combination of artificial diets that would allow raising of razorback suckers from sac-fry to fingerlings with high growth and survival. MATERIALS AND METHODS -~ Eggs and milt were stripped from wild razorback suckers from the Green River near Jensen, Utah in May, 1989. Eggs were fertil- ized in the field and were transported to the U.S. Fish and Wildlife Service hatchery at Ouray, Utah. Fertilized eggs were disinfected in a 10% betadine solution for 10 minutes, then flushed, tempered to 210C, and placed in Heath~1 incubators. Eggs began hatching 71 hours after fertilization, and hatching was complete at 95 hours. Sac-fry (N = 3,482) were placed in a 70-1 wooden tank supplied with heated, degassed and aerated, single-pass well water (flow = 41/minute; average temperature = 19.30C; average dissolved oxy- 1. Use of trade or manufacturer names does not imply endorsement by the U.S. Fish and Wildlife Service. I