9720

• UCREFRP Catalog Number: 9720
• Author: U.S. Fish and Wildlife Service.
• Title: Razorback sucker ‎(Xyrauchen texanus)‎ genetics management and captive propagation plan, Dexter National Fish Hatchery and Technology Center.
• USFW Year: 2004.
• USFW - Doc Type: Dexter National Fish Hatchery and Technology Center
• Copyright Material: NO

Geography of Razorback Sucker Distribution
Upper Colorado River Basin Recovery Unit
Green River/Yampa River System
Today, the RBS in this system exist as a small, non-recruiting, riverine population
supporting 500 to 1000 individuals (Lanigan and Tyus 1989; Modde et al. 1995), and a diminishing
riverine population of less than 100 adults in the middle Green River, between the confluences of
the Yampa River and the Duchesne River-(Modde et al. 1996; Bestgen et al. 2002). Historically,
the lower Yampa River and Green River provided numerous spawning and rearing sites for RBS
(Holden 1973; Minckley et al. 1991). It is unknown if this reach supported RBS populations that
were genetically isolated from the mainstem Colorado River population. Evidence is provided that
as recently as the late 1980s several putative spawning aggregations were present in the middle
Green River and lower Yampa River (Tyus 1987; Tyus et al. 1982). Recently, a few larval and
juvenile razorbacks were collected in the Green River, and it appears that these fish originated from
the middle section (Chart et al. 1999, Muth et al. 2000). In 1989, wild adults were collected from
the middle Green River at Jensen, Utah, downstream of the Ouray National Wildlife Refuge, and 20
adults from the San Juan arm of Lake Powell were also collected to begin development of a captive
broodstock at the Ouray National Fish Hatchery (Ouary NFH) on the Green River near Vernal,
Utah. The San Juan adults were later transferred to the Grand Valley Endangered Fish Facility.
Captive spawning strategies used at Ouray are those identified in the Genetic Guidelines, Recovery
Implementation Program for Endangered Fish Species in the Upper Colorado River Basin (U.S.
Fish & Wildlife Service 1994). From 1989 to 1991 three lots of future broodstock (one annually)
were created using a mixed stock of 15 females and 13 males of Green River origin. From 1993 to
2001, 25 unique family lots were created using predominantly the Green River stock. Two of the
lots created in 2001 are from F 1 parents of the San Juan and Colorado River arms of Lake Powell.
Fish were obtained for these matings from the Grand Valley Endangered Fish Facility. Each family
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