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METHODS Fish Propagation and Stocking The Genetics Management Plan (Williamson and Wydoski 1994; Wydoski 1995; Czapla 1999) identified the need for 25 fanvly lots for razorback sucker propagation efforts. Ultimately, razorback sucker produced from such propagation efforts would be stocked in two stream reaches in the Upper Colorado River (Rifle to Debeque Canyon [RM 240-203] and Palisade to Westwater [RM 185-128]) and one river reach in the Gunnison River (Hartland Diversion Dam to Redlands Diversion Dam [RM 60-3]). However, in the Upper Colorado and Gunnison rivers, numbers of wild razorback sucker were insufficient for collection and use in a 5 X 5 di-allele breeding matrix to even attempt to develop broodstock. Additionally, razorback sucker located in Etter Pond near Debeque, Colorado, were determined to be dominated by potential siblings from a very small number of parents, and potentially hybridized with flannelmouth sucker. Therefore, mating crosses between any two individual fish from Etter's Pond were determined to be genetically unacceptable due to the risk of inbreeding. However, since there was an insufficient number of razorback sucker broodstock, managers decided that a limited number of Etter Pond razorback sucker could be used if they were crossed only with wild Colorado River broodfish (personal communication, Mike C. Baker, FWS, Grand Junction, Colorado). Therefore, the RP approved development of a "blended stock" of razorback sucker to serve as the broodstock for the Upper Colorado and Gunnison rivers. A captive breeding strategy for these fish was described in Burdick et al. (1995) which followed the RP's Genetics Management Guidelines (Williamson and Wydoski 1994; Wydoski 1995). Fifteen wild adult razorback sucker obtained from four different sources in the Upper Colorado River Basin were used to produce offspring for stocking and for future broodstock (Appendix; Table A.1.). These fish were collected from the Colorado River arm of Lake Powell (4 fish), the Upper Colorado River near Grand Junction (4 fish), the San Juan River arm of Lake Powell (4 fish), and Etter Pond (3 fish). All adult fish used in the breeding scheme were PIT tagged to identify pedigree of offspring produced. The initial breeding matrix used is provided in Appendix; Table A.2. Most of the razorback sucker stocked in the Upper Colorado and Gunnison rivers were produced from wild and first generation (F,), domestic-reared broodstock. The progeny were obtained from paired matings of these captive wild fish, of wild and captive domestic-propagated broodfish (F,), and of captive (F,) broodfish. Between 1992 and 2001, eight year classes comprising eighty-one different family lots of razorback sucker were produced (Appendix; Table 9