7802 - Laserfiche WebLink

Home Browse Search

quality and stream flow on game fish (G, C. Powell 1958; Weber 1959; Coon 1965), In March 1963, Secretary of the Interior Stewart Udall requested the Utah Cooperative Fishery Research Unit to investigate changes in habitat and fish populations of the Green River in Dinosaur NM, Colorado-Utah, result- ing from the I962. poisoning operation and closure of Flaming Gorge Dam. These studies, conducted between I963 and I966, concluded that cold-water releases caused the disappear- ance of Colorado squawfish, bony tail, hump- back chub, and razorback sucker from the I05-km reach below the dam (Vanicek 1967; Vanicek et al,. 1970). The studies also found that the Green River below its confluence with the Yampa River still contained the endan- gered Colorado River fishes, a presumed con- sequence of the Yampa's ameliorating effect on water temperature. Work by the Cooperative Fishery Unit dur- ing 1963-1966 focused on basic life history of the Colorado squawfish and bony tail (Van- icek 1967; Vanicek and Kramer 1969; Van- icek et al. 1970) and on macroinvertebrate abundance and distribution (Pearson 1967; Pearson et al. 1968). These studies suggested that year classes of Colorado squawfish were strong in I959, 1961, 1963, 1964, and possi- bly 1966 (Vanicek 1967), but weak in 1962. and 1965. Formation of strong year classes during years when stream flow and water tem- peratures are more suitable for survival of re- cruits could be an evolutionary life-history strategy of this species (Tyus I986, this vol- ume, chap. I 9). Vanicek (I 967) also reponed difficulty in separating the various species of Gila, especially during early life stages. This led to a study of Gila taxonomy by Holden (1968; Holden and Stalnaker 1970), but the taxonomic questions were not fully answered. In 1988 the USFWS contracted with the Smith- sonian Institution to review and develop a program to resolve the problem. Holden (1973) studied relative abundance Evolutio/l of a Rccovery Prograll/ I 2.9 and distribution of native fishes in the upper basin and documented problems with recruit- ment of squaw fish in Echo Park (Dinosaur NM), where juveniles were abundant in 1968, scarce in 1969, and nonexistent in [970. However, he reported young-of-year in Deso- lation Canyon in 197 I, and in the Green River in Canyonlands National Park in 1970 and [971. During [974-1976, studies focused on obtaining further life-history information (McAda 1977jSeethaler 1978), McAda ([977; McAda and Wydoski 1980) provided new bio- logical information and synthesized all knpwn life-history data on razorback suckers In the upper basin. Seethaler (1978) provided a com- prehensive summary of the life history of Col- orado squawfish, including the first data on reproduction, fecundity, maturity, and early development. An annotated bibliography as- sembled in I976 and updated in 1980 listed studies of the native fishes and macroinverte- brares, and provided selected references that discussed economic, political, and sociologi- cal factors confounding management of Colo- rado River fishes (Wydoski et al. (980). Stud- ies of macroinverrebrates were completed by Carlson et al. (1979). Colorado River Fish Project The requirements of section 7 of the ESA had potentially serious ramifications for new water projects proposed by the USBR, and for the op- eration of several of their existing facilities such as Flaming Gorge and Blue Mesa reser- voirs, However, lack of data on in.stream flow and other habitat requirements of endangered Colorado River fishes was recognized by both the USBR and USFWS as a serious impediment to the development of reasonable and prudent alternatives for operating existing, and design- ing proposed, projects. As a result, the USBR agreed to provide funding to gather essential information on ecological requirements of the ra re fishes.