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CHAPTER III AFFECTED ENVIRONMENT I B. Rare and Endangered Fishes Six endemic fishes are endangered or rare in the Upper Colorado River Basin. The Colorado squawfish, bonytail chub, humpback chub, and Kendall Warm Springs dace are federally listed as endangered (Table III-B-1). Two other fishes not listed, but identified by the Secretary of the Interior as candidates for listing, are the razorback sucker and the Colorado River cutthroat trout. As noted earlier the term "rare" will be applied to encompass both rare and endangered species. Two rare fishes are confined to restricted geographic areas: the Kendall Warm Springs dace and the Colorado River cutthroat trout. The Proposed Action is not directed toward these species. They are discussed in Sections III.F and IV.F, "Other Endangered and Threatened Species." The Proposed Action is directed toward the remaining four fish: Colorado squawfish, humpback chub, bonytail chub, and razorback sucker. These warmwater fish inhabit the mainstream and major tributaries of the Green and Colorado Rivers and are considered large river species. The remainder of this discussion describes these species. The past and present distribution and sensitive areas, geographic areas that are important for various life stages of the Colorado squawfish, humpback chub, bonytail chub, and razorback sucker in the Upper Basin, are illustrated in Figures III-B-1 through III-B-4, respectively. These illustrations, based on the Sensitive Areas Report by the Biological Subcommittee (1984) of the Coordinating Committee and more recent preliminary information and analyses, show the drastic reduction in the range of these fishes. An update to the 1984 Sensitive Areas Report is planned for 1988. The following is a review of present habitats used by these fishes in the Upper Basin (excluding the San Juan River). Colorado Squawfish Adult Colorado squawfish use a variety of habitat types, which vary depending on time of year. They use shoreline run, eddy, and backwater habitats during pre- and post-runoff periods. They utilize seasonally flooded bottoms and side canyons, eddies, runs, and backwaters during high flow periods. Adult Colorado squawfish are most abundant in the upper Green River (between the mouth of the Yampa River and head of Desolation Canyon) and lower Green River (between the Price and San Rafael Rivers) (Figure III-B-1). Other concentration areas include the Yampa River, the lower 21 miles of the White River, and the Ruby and Horsethief Canyon area between Westwater, Utah, and Loma, Colorado. Spawning occurs in July-August in the lower 30 miles of the Yampa River and in Gray Canyon in the lower Green River. Suspected spawning sites are shown in Figure III-B-1. III-6