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<br />ECOLOGY AND CONSERVATION OF NATIVE FISHES IN THE UPPER COLORADO RIvER BASIN
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<br />yon before it was inundated by Flaming Gorge Res-
<br />ervoir, but numbers and sizes are unknown because
<br />they were grouped with humpback chub and
<br />roundtail chub. "Bony tail chub," roundtail chub,
<br />and humpback chub were reported in the Green
<br />River from the mouth of the Black's Fork River
<br />downstream through Flaming Gorge (Bosley
<br />1960), and composed 7.3% of all fish from Green
<br />River, Wyoming, to the Utah-Colorado state line
<br />(McDonald and Dotson 1960). Individuals col-
<br />lected from the base of Flaming Gorge Dam and
<br />from Little Hole (10 km below the dam) in 1962
<br />are held at the University of Michigan (R. Miller,
<br />University of Michigan, personal communication;
<br />Bookstein et al. 1985). Bony tail outnumbered
<br />roundtail chub in the Green River for the 1959,
<br />1960, and 1961 year classes with 67 bonytail more
<br />than 200 mm TL collected during 1964-1966
<br />(Vanicek and Kramer 1969). Holden and Stal-
<br />naker (1975b) reported 36 bonytail from the lower
<br />Yampa River and middle and lower Green River
<br />during 1967-1973. Bonytail declined dramatically
<br />in the Green River through the 1960s. Reasons for
<br />the decline are unknown, but were likely related to
<br />the closure of Flaming Gorge Dam in 1964. Before
<br />filling Flaming Gorge Reservoir, about 725 km of
<br />the Green River and its tributaries were treated with
<br />rotenone to poison nonnative carp, catfish, shiners,
<br />and perch in advance of stocking the reservoir with
<br />rainbow trout Oncorhynchus mykiss and kokanee 0.
<br />nerka (Holden 1991). Fish surveys after the closure
<br />of Flaming Gorge Dam revealed that the rotenone
<br />had not killed all of the fish in the treatment area
<br />and did not eliminate the native forms, including
<br />bonytail, roundtail chub, humpback chub, Colo-
<br />rado pikeminnow, and razorback sucker (Banks
<br />1964). These surveys concluded that subsequent
<br />reductions in native fish populations occurred pri-
<br />marilyas a tesult of reservoir flooding of habitat,
<br />and changes in river flows and water temperatures
<br />from dam operations.
<br />By the late 1970s, few bonytail were reported
<br />from the upper basin (Figure 4), including two
<br />from the Green River below Jensen, Utah (Joseph
<br />et al. 1977). Bony tail were seen in Lake Powell
<br />soon after Glen Canyon Dam was closed in 1962
<br />(K. Miller, Utah Division of Wildlife Resources,
<br />
<br />personal communication), and two (330 and 380
<br />mm TL) were caught by anglers near Wahweap
<br />Bay on September 4, 1977 (Gustafeson et al. 1985)
<br />and in 1985 (R. Radant, Utah Division of Wild-
<br />life Resources, personal communication); the lat-
<br />ter fish was identified by Dr. Mark Rosenfeld (Uni-
<br />versity of Utah, personal communication), and a
<br />taxidermy mount is on display at the university's
<br />natural history museum. One adult bony tail was
<br />captured in the lower Yam pa River in 1979
<br />(Holden and Crist 1981), and one adult was caught
<br />and released at Coal Creek Rapid in the Green River
<br />in GrayCanyon in 1981 (Tyuset al. 1982). Kaeding
<br />et al. (1986) captured and released one adult
<br />bonytail (458 mm TL) in the Colorado River at Black
<br />Rocks on July 17, 1984. Two adult bonytail were
<br />captured, photographed, and released in Desola-
<br />tion/Gray Canyons in 1985 (Moretti et al. 1989),
<br />and four adults and one juvenile were reported from
<br />Cataract Canyon in 1985-1988 (Valdez 1990;
<br />Valdez and Williams 1993).
<br />Preferred habitat ofbonytail is undetermined,
<br />but large fins and a streamlined body suggest ad-
<br />aptation to torrential flows (Beckman 1963). Of
<br />11 wild adults captured in the upper basin since
<br />1977, nine were in deep, swift, rocky canyons (i.e.,
<br />Yampa Canyon, Black Rocks, Cataract Canyon,
<br />and Coal Creek Rapid), and two were in Lake
<br />Powell. Vanicek (1967) reported that bonytail were
<br />generally found with roundtail chub in pools and
<br />eddies in the absence of, but adjacent to, strong
<br />current and at varying depths over silt and boul-
<br />der substrates. Natural reproduction of bonytail
<br />was last documented in the Green River for the
<br />year classes 1959, 1960, and 1961 (Vanicek and
<br />Kramer 1969). Ripe spawning adults, 5-7 years
<br />of age, were captured from mid-June to early July
<br />at a water temperature of 180C (Vanicek 1967).
<br />Average fecundity is about 25,090 eggs per female,
<br />and incubation was shortest (99-174 h) and egg
<br />survival, hatching success, and larval survival were
<br />highest at 20-21 oC (Hamman 1985).
<br />
<br />Razorback Sucker
<br />Razorback sucker is a robust fish with maximum size
<br />of 1 m TL and 5-6 kg (Minckley 1973; Minckley
<br />et al. 1991); maximum age is up to 44 years
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