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Cl (".~ ...... Colonel John N Reese DRAFT 12 ....1 hydrograph from mid-April through June and are associated with coarse gravel en substrates (depending on the specific location). Outside of the spawning season, adult razorback suckers occupy a variety of shoreline and main channel habitats including slow runs, shallow to deep pools, backwaters, eddies, and other relatively slow velocity areas associated with sand substrates (Tyus 1987; Tyus and Karp 1989; Osmundson and Kaeding 1989; Valdez and Masslich 1989; Tyus and Karp 1990; Osmundson and Kaeding 1991). The virtual absence of any recruitment sU9gests a combination of biological, physical, and/or chemical factors that may be affecting the survival and recruitment of early life stages of razorback suckers. Within the Upper Basin, recovery efforts endorsed by the "Recovery Implementation Program for Endangered Fish Species in the Upper Colorado River" (U.S. Fish and Wildlife Service 1987), include the capture and removal of razorback suckers from all known locations for genetic analyses and development of discrete brood stocks if necessary. These measures have been undertaken to develop refugia populations of razorback sucker from the same genetic parentage as their wild counterparts such that, if these fish are genetically unique by subbasin or individual population, then separate stocks will be available for future augmentation. Such augmentation may be a necessary step to prevent the extinction of razorback suckers in the Upper Basin. Habitat requirements of young and juvenile razorback suckers in the wild are largely unknown, particularly in native riverine environments. Life stages, other than adults, have been extremely rare in the upper basin in recent times. One confirmed capture of razorback sucker juveniles in the upper basin was in the Colorado River near Moab, Utah (Taba et. al. 1965). The only capture.in recent years was the 1991 collection of two early juvenile razorback suckers in the lower Green River, 89.5 km above the confluence with the Colorado River. (Gutermuth et. al. 1994). Razorback Sucker Activitv in the San Juan River Because razorback suckers are so rare in the San Juan River and spawning or recruitment have not been documented, an experimental stocking program was initiated. In March of 1994, 15 radio-tagged razorback suckers were stocked in.the San Juan River at Bluff, Utah (RM 79.6); near Four Corners Bridge (RM 117.5); and above the Mixer in New Mexico (136.6). In November 1994 an additional 15 radio-tagged adults and 656 PIT-tagged fish were stocked in the same locations as well as an additional site just below the Hogback Diversion in New Mexico (RM 158.5). Monitoring found that these razorback suckers used slow or slackwater habitats such as eddies, pools, backwaters, and shoals in March and April and fast water 92.2 percent of the time in June and August (Ryden and Pfeifer 1995b).. During 1995 both radio-tagged fish and PIT-tagged fish.were contacted or captured. Razorback suckers were found in small numbers from the Hogback Diversion (RM 158.6) to 38.1 river miles above Lake Powell (D. Ryden, pers. comm.).