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<br />Great Basin Naturalist 50(a), 1990, pp. 257-264
<br />HUMPBACK CHUB (GILA CYPHA) IN THE YAMPA AND GREEN RIVERS,
<br />DINOSAUR NATIONAL MONUMENT, WITH OBSERVATIONS ON
<br />ROUNDTAIL CHUB (G. ROBUSTA) AND OTHER SYMPATRIC FISHES
<br />Catherine A. Karel and Harold M. Tyust
<br />~~~a~j~
<br />ABSTRACT.-We evaluated distribution, habitat use, spawning, and species associations of the endangered humpback
<br />chub (Gila ct~pha) in the Yampa and Green rivers, Dinosaur National Monument, from 1986 to 1989. Adult and juvenile
<br />humpback chub were captured in high-gradient reaches of Yampa and Whirlpool canyons where they were rare (n =
<br />133, <1% of all fish captured). The fish was primarily captured in eddy habitats in association with 7 native and 12
<br />nonnative fish species. Roundtail chub (G. rob~usta) were widely distributed in eddies, pools, nms, and rifles.
<br />Humpback chub (n = 39) and roundtail chub (n = 242) in reproductive condition were sympatric in eddy habitats
<br />during the 5-6-week period following highest spring runoff. River temperatures at this time averaged about 20 C.
<br />Normative channel catfish (Ictalurus punctatt~ )were abundant in eddies yielding humpback and roundtail chubs,
<br />suggesting a potential for negative interactions between the native and introduced fishes.
<br />The humpback chub (Gila c~pha), a large-
<br />river cyprinid endemic to the Colorado River
<br />basin of western United States, is federally
<br />protected by the Endangered Species Act of
<br />1973. The fish persists only in isolated loca-
<br />tions, including canyon reaches in the Little
<br />Colorado and tainstream Colorado rivers,
<br />Arizona (Kaeding and Zimmerman 1983), up-
<br />per Colorado River, Colorado (Valdez and
<br />Clemmer 1982, Kaeding et al. 1990), Green
<br />and Yampa rivers, Colorado and Utah (Hol-
<br />den and Stalnaker 1975a, 1975b, Tyus et al.
<br />1982), and mainstream Colorado River, Utah
<br />(Valdez 1990). All stocks are presumed native
<br />except in Cataract Canyon of the Colorado
<br />River, Utah, where some fish may be derived
<br />from a 1981 stocking of juvenile fish of up-
<br />per Colorado River (Black Rocks) parentage
<br />(J. Valentine, personal communication).
<br />Distribution and status of humpback chub
<br />in the upper Green and lower Yalnpa rivers
<br />in Dinosaur National Monument (DNM) re-
<br />main poorly documented, partly because
<br />canyon-bound whitewater habitats are diffi-
<br />cult to access and sample, the fish is rare, and
<br />diagnostic features are not well established.
<br />Humpback chub were first reported in DNM
<br />in the 1960s, and most captures occurred in
<br />the confluence area of the Yampa and Green
<br />rivers (Holden and Stalnaker 1970, 1975a,
<br />1975b, Vanicek et al. 1970). Studies in the
<br />mid-1970s and early 1980s also noted the
<br />paucity of the fish in DNM (Seethaler et al.
<br />1979, Miller et al. 1982).
<br />Roundtail chub (Gila robusta) are sym-
<br />patric with humpback chub in DNM but are
<br />more widely distributed and more abundant
<br />(Banks 1964, Vanicek et al. 1970, Holden and
<br />Stalnaker 1975, Miller et al. 1982). The fish is
<br />not considered threatened or endangered un-
<br />der the Endangered Species Act of 1973. Re-
<br />mains of Gila species in Indian sites in DNM
<br />dating more than 1000 years old (Leach 1970)
<br />suggest that chub were presumably eaten by
<br />Native Americans and thus have been present
<br />in the area for a long time.
<br />This study was initiated as part of a larger
<br />program to assess status and habitat needs
<br />of endangered fishes in the Yampa River
<br />(Tyus and Karp 1989). Our objectives were
<br />to locate humpback chub in DNM and, if
<br />successful, evaluate habitat use (including
<br />flow and temperature requirements), identify
<br />spawning areas, and determine species asso-
<br />ciations.
<br />METHODS
<br />The lower 73.6 km of the Yampa River (i. e. ,
<br />Yampa Canyon: Deerlodge Park to Echo Park;
<br />Fig. 1) was sampled weekly from mid-May
<br />through early July 1987-1989 by electrofish-
<br />ing and angling with native foods (e. g. , Mor-
<br />mon crickets [Anabrus simplex ] and mega-
<br />lopteran larvae) and night crawlers at vari-
<br />ous locations in the water column. Echo and
<br />Island parks and Whirlpool and Split Moun-
<br />tain canyons of the Green River were sampled
<br />lU. S. Fish and Wildlife ServSee, 1680 W. Highway 40, Vernal, Ukah 84978.
<br />257
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