7309 - Laserfiche WebLink

Home Browse Search

1:. 4. } yus. ,. III. Vcdde:-t cr V\) i (( I C.)t-,\5 ) jqf6 / ~ /(lI;l/~rI3J$) / j v "'^') I 07 :g()q ;P-j STATUS OF ENDANGERED FISHES IN THE UPPER COLORADO RIVER, 1985 H.M. TYUS, R.A. VALDEZ, AND R.D. WILLIAMS U.S. FISH AND WILDLIFE SERVICE, VERNAL, UTAH 84078 BIOWEST INCORPORATED, LOGAN, UTAH 84321 U.S. BUREAU OF RECLAMATION, SALT LAKE CITY, UTAH 84147 ABSTRACT The current distribution and status of three federally protected endangered fishes, Colorado squawfish, hump- back chub and bony tail , are presented for the Green, Upper Mainstem Colorado, and San Juan-Colorado subre- gions. The distribution and status of the humpback chub has not changed since 1981; however, the Colo- rado squawfish subpopulation in the upper White River has been fragmented. The paucity of confirmed bony- tail specimens casts doubt upon the survival of this form in the upper Colorado River, and a review of Gila specimens recently captured from the Upper Basin suggests the existence of a polymorphic complex. The razorback sucker, not currently protected under the Endangered Species Act, is considered imperiled, and its low numbers and the possible absence of recruit- ment indicate its existence is precarious. The con- cept of sensitive areas for habitat protection is discussed. I NTRODUCTI ON The demand for water resources development in the predominantly arid Colorado River Basin has placed a great demand upon scarce water supply. Environmental alterations, including changing land and water use and the introduction of exotic species, have degraded the native fish fauna of the Colorado; its endemic fishes, uniquely adapted to the hostile river system, are exposed to new stresses which threaten them with extinction. Although mainstem rivers are still occupied by endemic fishes, historic ranges have been markedly reduced. Three species of mainstem endemic fishes of the Colorado River are presently listed as endangered under the Endangered Species Act of 1973. These are the Colorado squawfish (Ptychocheilus lucius), humpback chub (Gila cypha), and bony tail (Gila elegans). The razor- back sucker (Xyrauchen texanus), not federally listed, is protected by several states, including Utah, and is listed endangered by -20- i: