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. . I larval stages of these fishes were completed at Colorado State University by Muth (1988). The San Juan River -- The Forgotten River Basin The San Juan River originates in the mountains of southwestern Colorado, flows southerly into Navajo Reservoir, then east through the deserts of New Mexico and Utah where it eventually joins the Colorado River in Lake Powell (Figure 8-1). Historically, the San Juan River provided habitat for the Colorado squawfish, the razorback sucker, and perhaps the bony tail. However, the common name II bony tail II was used for other Gila species, particularly the roundtail chub (~. robusta) in the upper basin so the presence of bony tail in ~ the San Juan is questionable. Limited surveys of the river resulted in the capture of one juvenile Colorado squawfish at the mouth of McElmo Creek near Aneth, Utah (VTN Consolidated, Inc. 1978). In addition, an effort was made to eradicate native "rough" fish prior to the closure of Navajo Reservoir (Olson 1962). Only four large Colorado squawfish were documented to have been killed during the eradication effort (Olson 1962). Similar to the impacts to the endemic fish in the Green River, the long-term changes in habitat, streamflow, and water temperature from construction and operation of Navajo Reservoir (and perhaps Lake Powell) are probably most responsible for the decline of the Colorado squawfish in the San Juan River. Until recently, the San Juan River was relegated to a relatively low priority in upper basin recovery efforts for the endangered fishes. The low priority is most attributable to the USFWS 1979 biological opinion on the proposed Animas-LaPlata Project. This opinion concluded that "because of the apparent small size of the San Juan River squawfish population and its