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4 Ecology of Bonytail and Razorback Sucker confirmed wild bony tail was taken in the Lower Basin in the mid-1990's, and the last capture in the Upper Basin occurred in 1985 (Valdez and others, BIO- WEST, Inc., written comm., 1994; Marsh, 1997a). Bony tail are being supplemented by stocking with no recruitment in nature reported except volun- teer spawn in rearing ponds (Pacey and Marsh, 1998). Status of the Razorback Sucker This fish was federally listed as endangered on 23 October 1991 (56 FR 54957). A final rule designating criti- cal habitat was published on 21 March 1994 (59 FR 13374). Wild fish have been reduced (circa 2005) to about 500 in Lake Mohave, 300 in Lake Mead, <50 in Senator Wash Reservoir (Ulmer and Anderson, 1985), and 100 in the Green River, Utah (Holden and others, 1997; Bestgen and others, 2002; Paul Marsh, Arizona State University [ASU], oral commun., unpublished data, 2004). Wild populations are extirpated from the Salt, Gila, Gunnison, San Juan, and Upper Colorado Rivers and portions of the basin south of the international border (USFWS, 2002b). Relic populations are in rapid decline and are being augmented or reestablished through stocking. Natural sustainable recruitment in the mainstem river has been absent or minimal for several decades. Propagation and Stocking Propagation and stocking are the only actions that have prevented the extirpation of bony tail and razorback sucker from the Colorado River. Initially, literally millions of small fish were stocked. Today, fewer but larger fish are stocked to increase survival (Mueller, 1995; Burdick and others, 1995; Ryden, 1997). Propagation efforts were started almost too late for bony- tail. This species was allowed to become so rare that it nearly became extinct. The existing hatchery stocks can be traced back to possibly three females (Minckley and others, 1989; Hedrick and others, 2000). Potential problems associated with genetic bottlenecks in such a small broodstock have resulted in recommendations to maintain better genetic diversity in hatch- ery broodstock (Dowling and DeMarais, 1993; Hedrick and others, 2000). Propagation of razorback sucker proceeded with greater caution, resulting in three separate efforts designed to maintain the remaining genetic diversity for that species. These include two locations in the Upper Colorado River Basin and one in the Lower Basin. Seven facilities are being used to propagate either bony- tail, razorback sucker, or both to be stocked into the Colorado River Basin (table 1). Wild bony tail and razorback sucker were first collected from Lake Mohave beginning in 1974 and trans- ported to Willow Beach National Fish Hatchery (WBNFH) (Toney, 1974; Minckley and others, 1991). Dexter National Fish Hatchery and Technology Center (Dexter NFHTC) began operation in 1980, where broodstock were developed for both species (Minckley, 1985) (fig. 2, table 1). Dexter NFHTC maintains the only existing broodstock for bony tail. Stocking in the Lower Colorado River Basin began in 1981 (Johnson, 1985; USFWS, 2002a), and during the past 25 years, Dexter NFHTC alone has produced more than 2.1 million bony tail and 15 million razorback sucker (Dexter NFHTC, unpublished data, 2004). Dexter NFHTC maintains a broodstock of 300 razorback sucker and produces young suckers that are either directly stocked downstream of Davis Dam (USFWS, 1993) or are grown out at other facilities to be stocked elsewhere. The Upper Basin Recovery Implementation Program (RIP) identified a minimum of three and possibly five unique genetic strains of razorback sucker in the Upper Colorado River (Tom Pitts, Hall Pitts and Assoc., written commun., 1997; Czapla, 1998). There were only sufficient numbers of surviving fish to attempt development of two separate broodstocks of Upper Basin fish: one at Ouray National Fish Hatchery (Ouray NFH) located near Vernal, Utah (fig. 3), and the other at the Grand Valley Facility at Grand Junction, Colorado. The Ouray NFH broodstock was established on the premise that fish surviving in the Green River possessed unique survival characteristics worth preserving (Williamson and Wydoski, 1994). Their broodstock was made up primarily of wild fish taken from the Green River or their progeny. The facility has 36 ponds, isolation tanks, and a hatchery building. Razorback sucker produced there are stocked in the Green River, with surplus fish going toward Grand Valley stocking commitments. The Grand Valley Facility maintains approximately 300 razorback sucker for broodstock that represent a mixture of fish originating from stock taken from the Green River, fish from the Lower Basin, and a few surviving fish from the Upper Colorado River. Production meets stocking goals for the Gunnison, Colorado, and San Juan Rivers. In addition, there are several facilities in the Upper Colorado River Basin that utilize fish produced from the two facilities. The San Juan "="'.- - c~."" .-:.:.,,,,,",""'..."W,,..,,.,,,__. .c-:,,,'! - ~~~~ Fig. 2. Aerial photograph of Dexter National Fish Hatchery and Technology Center's rearing ponds located near Dexter, New Mexico. Photo courtesy of Manuel Ulibarri, U.S. Fish and Wildlife Service.