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zl Boaytail 4n ; a~j-i ti d Habifa D a ~ ion Bonytail are medium-sized (less than 600 mm) fish in the minnow family. Adult bonytail are gray or olive colored on the back with silvery sides and a white belly. The adult bonytail has an elongated body with a long, thin caudal peduncle. Critical habitat was designated in 1994 within the bonytail's historical range in the following sections of the Upper Colorado River (59 F.R. 13374). The primary constituent elements are the same as those described for the Colorado pikeminnow. LTt ah. Grand Coln ty: and ofo ado. MPSa Co ,n ty. The Colorado River from Black Rocks (river mile 137) in T. 10 S., R. 104 W., section 25 (6th Principal Meridian) to Fish Ford in T. 21 S., R. 24 E., section 35 (Salt Lake Meridian). T.ah. ,art; ld nd can T,an o,*, ;.a, The Colorado River from Brown Betty Rapid in T. 30 S., R. 16 E., section 34 (Salt Lake Meridian) to Imperial Canyon in T. 31 S., R. 17 E., section 28 (Salt Lake Meridian). S a ,s and Dis i b , inn The bonytail is the rarest native fish in the Colorado River. It was listed as endangered April 23, 1980. Formerly reported as widespread and abundant in mainstem rivers (Jordan and Evermann 1896), its populations have been greatly reduced. The fish is presently represented in the wild by a low number of old adult fish in Lake Mohave and perhaps other lower basin reservoirs (USFWS 1990a). The last known riverine area where bonytail were common was the Green River in Dinosaur National Monument, where Vanicek (1967) and Holden and Stalnaker (1970) collected 91 specimens during 1962-1966. From 1977 to 1983, no bonytail were collected from the Colorado or Gunnison Rivers in Colorado or Utah (Wick et al. 1979, 1981; Valdez et al. 1982b; Miller et al. 1984). However, in 1984, a single bonytail was collected from Black Rocks on the Colorado River (Kaeding et al. 1986). Several suspected bonytail were captured in Cataract Canyon in 1985-1987 (Valdez 1985, 1987, 1988). The existing habitat has been modified to the extent that it impairs essential behavior patterns, such as breeding, feeding, and sheltering. The bonytail is considered a species that is adapted to mainstem rivers, where it has been observed in pools and eddies (Vanicek 1967;