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13376 Federal Register / Vcl. 59, No. 54 / Monday, March 21, 199-1 / Rules and Regulations 4'` 1 ephemeral Along-share embayments that develop as spring flows decline. Humpback Chub Remains of humpback chub have been found in archaeological sites dated to about 4000 B-C. (USFWS 1990b). This Colorado River native fish was not described as a species until 1946 (Miller 1946). This has been attributed to its presently restricted distribution in remote, white water canyons (USFWS 1990b). The historical abundance and distribution of the.species is not well known. In the Lower Basin, the humpback chub occurs in the little Colorado and Colorado Rivers in the Grand Canyon. This population is the largest remaining in the Basin. In the Upper Basin. humpback chub arefvnnd in the Black Rocks/Westwater Canyon and Cataract Canyon of the Colorado River, Desolation and Gray Canyons of the Green River, and Yampa and Whirlpool Canyons in Dmosaur National Monument, Green and Yampa Rivers {USFWS'1990b). humpback chub in reproductive condition are usually captured in May. June. or July, depending on location. Spawning occars soon alter the highest spring flows when water temperatm es approacli W*C (68'F) Wup and 1990; USFWS 1990b).''he importance of spriog flows and proper tempmatares for humpback club is stressed by Kaeding and Timmerman 11983). who implicated Bow mdrmtions and low water temperertmes in the d Canyon as factors cmemifing spawning of the fish and increasing competition from ours species. Popalassms of humpbick chub are found in river canyons, where they utilize a variety of habitats, inchrding pools. riIDes, and eddies Most of the existing infiocmation on habitat preferences has been obtained from adult fish in the Little Colorado River, the Grand Canyon, and the Black Rocks of the Colorado River IHolden and Stalnaker 1975; Kaeding and Zimmerman 1983; Kaeding et aL 1990). In these locations, the fish are found associated with boulderstrsu;i canyons., travertine dams, pools, and eddies. Some habitat-use data also are available from the Yampa River Canyon where the fish occupy similar habitats and also use rocky runs, riffles, rapids, and shoreline eddies (Karp and Tyus 1990). This diversity in habitat use suggests that the adult fish are adapted to a variety of habitats, and studies of tagged fish'indicated that they move between habitats, presumably in response to seasonal habitat changes and life history needs (Kaeding and Zimmerman 1983; Karp and Tyus 1990). Reduced spring peak flows, availability of shoreline eddy and deep canyon habitats, and competition and predation by nonnative fish were reported as potential limiting factors for humpback chub in the Yampa River (Tyus and Karp 1989). The impact of hybridization with other species is currently being evaluated. Bonytail Chub The bonytail chub (also known as the bonytail) is the rarest native fish in the Basin. Historically reported, as widespread and abundant in rivers throughout the Basin Qordan and Evennann 1896), its populations have been greatly reduced. The fish is Presently represented in the wild by a low number of old fish fi.e., ages of 40 Years or morel. and recruitment is virtually none ste=. in the Lower Basin, a small population persists in the Colorado River in Lake Mohave, and there are recent records from Lake Havasu WSFWS 19904. In the Upper Basin.. recent captures have been from Dinosaur National Monument on the Yampa River, Desolation and Gray Canyons on the Green River, and Black Rocks and Cataract Canyon on -the Colorado River Maeding et aL 1986; Tyus et al. 1987; Valdez 1990; USFWS 1990a). The banytaii chub is adapted to mainstream rivers, where it has been observed in pools and eddies 1Minckiey 1973; Vanicek 1967). In reservoirs, the fish occupies a variety of habitat types (Mine kley 1973). In Lake Mohave, Wagner 11955) observed the fish in eddy habitats. Spawning requirements have never been docurmented in a river, but Vanicek and Krmer (1969) reported that spawmmg occurred in June and July at water tempemhmes of about Tr C (64° F). The available data suggest that habitats required for conservation of the bonytail chub include, river channels, and flooded, ponded, or inundated rirerine habitats that would be suitable for adults and young, especially if competition from normative fishes is reduced (USFWS 1990a). Previous Federal Actions Listing Chronology The Colorado squawfish and humpback chub were listed as endangered species on March 11. 1967 (32 FR 4001) and the bonvtail chub was listed as endangered on April 23. 1980 (45 FR 27713). Critical habitat for these species was not designated at the time of their listing On May 16, 1975, the Service published a notice of its intent to determine critical habitat for the Colorado squawfish and the humpback chub, and other species (40 FR 21499). On September 14, 1978, the Service. proposed 1,002 km (623 mij of the Colorado. Grew. Gunnison. and Yamp2 Rivers as critical habitat for the Colorado squawfish (43 FR 41060). The proposal was for 1,002 km (623 mi) of the Colorado, Green, Gunnison, and Yampa Riven. Tins proposal was later withdrawn (44 FR 123aZ- March 6, 1979) to comply with the 1978 amendments to the Act (16 U.S.C. 1531 et sr;+q.). The razmba k sucker was first proposed for listing as a threatened species on April 24, 1978 (43 FR 17375). The proposal was withdrawn on May 27, 1980 (45 FR 35410), to comply with provisions of the 1978 amendments to the Act. These provisions required the Service to include consideration of designating critical habitat in the listing of species, to complete the listing process within 2 years from the date of the proposed rule, or withdraw the proposal from further consideration. The Service did not complete the listing process within the 2-year deadline. On March 15. 1989. the Service received a petition from the Sierra Club, National Audubon Society. The Wilderness Society Colorado Environmewai Coalition, Southern Utah Wilderness Alliance, and Northwest Rivers Alliance to list the razorback sucker as endangered, The Service made a positive findigg in June 1988 and subsequently published a notice in the Federal RegisEeron August 15. 1989 (54 FR 33586). This notice also stated that the Service was completing a statics review and was seeking additional information until December 15. 1989. A proposed rule to list the razorback sucker as endangered was published in the Federal Yegister on May 22, 1990 (55 FR 21154)_ The final rule listing the razorback sucker as an endangered species was published on October 23, 1991 (56 FR 54957), but critical habitat was not proposed. In the final rule, the Service concluded that critical habitat was not determinable at the time of listing and questioned whether it was prudent to designate critical habitat. On October 30. 1991, the Service received a 60-day notice of intent to sue from the Sierra Club Legal Defense Fund. The subiect of the notice was the Service's failure to designate critical habitat concurrent with listing of the razorback sucker pursuant to section 4(by6)(c) of the AcL The Sierra Club Legal Defense Fund followed this with a second notice of intent to sue dated January 30, 1992. Al a meeting on December 6, 1991, the Service concluded that designation of critical 1 1 1