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1991. During this same period, 95 razorback sucker were collected from the Green River (Table 1). Total numbers of razorback sucker collected from the upper Colorado River declined dramatically from 1979 through 1992. Fifty-two razorback sucker were collected during 1979-1981 from Lake Powell to Rifle, Colorado (Valdez et al.1982); 35 razorback sucker were collected during 1982- 1985 (Archer et al. 1985); and seven fish were collected from 1986-1989 (Osmundson and Kaeding 1989a) (Appendix Table 2; Figure 2). In 1990 and 1991, an effort was undertaken to collect razorback sucker from portions of the upper mainstem Colorado River to establish a broodstock refugia population. Areas that were searched included stream reaches from Rifle to the Utah/Colorado state line, Highline Reservoir (near Loma, Colorado), and ponds adjacent to the river in these stream sections. Despite extensive effort, no razorback sucker were collected or observed in the river sections searched. So few adult riverine fish remain that it is unlikely that a mature male and female razorback sucker would be concurrently attracted to the same spawning area. However, four adult razorback sucker were captured from Highline Lake in 1990. Fourteen additional razorback sucker were captured in 1991 from two different isolated ponds between Rifle and Government Highline Diversion Dam. One was captured in April from an isolated gravel-pit downstream of Rifle and 13 razorback sucker were collected from the second pond near Debeque, Colorado in August. Twelve additional adult razorback sucker were captured by Colorado Division of Wildlife (CDOW) personnel from this same pond in April 1992. These fish were released back into this pond. The genetic structure of the various razorback sucker populations has not yet been defined. Assessing the existing genetic material for all possible 4 r