Laserfiche WebLink
<br />-, <br /> <br />5 <br /> <br />America and. ckJrillg predevelopment times, may have grown as large as 6 feet in <br />length and weighed nearly 100 pounds (Behnke and Benson 1983>' These large fish <br />may have been 25 to 50 years of age. <br /> <br />Based on earl} fish collection records, archaeo 1 ogi ca 1 fi nds. and other <br />observations, the Colorado sQuawfi sh was once found throughout warmwater reaches <br />of the entire Colorado River Basin. including reaches of the upper Colorado <br />River and its lli!jor tributaries. the Green River and its major tributaries, and <br />the Gila River systell in Arizona (Seethaler 1978>' Colorado sQuawfish were <br />apparently never f~ in colder. headwater areas. Seethaler (1978) indicates <br />that the species was abundant in suitable habitat throughout the entire Colorado <br />River Basin prior to the 1850's. Historically. Colorado sQuawfish have been <br />collected in the upper Colorado River as far upstream as Parachute Creek. <br />Colorado CKidlll9m. <br /> <br />A marked decline i. Colorado sQuawfish populations can be closely correlated <br />with the constrllctiOl of dams and reservoirs during the 1960's. the introduction <br />of nonnative flUes. and the removal of water from the Colorado River system. <br />Behnk.e and BeIISOII (1983) summari zed the dec line of the natura I Colorado Ri ver <br />ecosystem. They poi.ted out that dams. impoundments. and water use practices <br />are probably thelli!jor reasons for drastically modified natural river flows and <br />channel Characteristics in the Colorado River Basin. Dams on the mainstem have <br />essentially segIEllted the river system. block.ing Colorado sQuawfish spawning <br />migrations and drastically changing river characteristics. especially flows and <br />tefllleratures. III addition. major changes in species cOlll>osition have occurred <br />due to the in~ion of nonnative fishes. many of which have thrived as a <br />result of cha11ge5 In the natural riverine system (i.e.. flow and temperature <br />regimes). The decline of endemic Colorado River fishes seems to be at least <br />partially related to competition or other behavioral interactions with nonnative <br />species, whidi IIive perhaps been exacerbated by alterations in the natural <br />fluvial enviru..t. <br /> <br />The Colorado 51111i111fi~ currently occupies about 1.030 river miles in the <br />Colorado River systell (25 percent of its original range) and is presently found <br />only in the !;per' Colorado River Basin above Glen Canyon Dam. It inhabits about <br />350 miles of die .il5tem Green River from its mouth to the mouth of the Yampa <br />River. Its JWge i150 extends 140 mil es up the Yampa River and 104 mil es up the <br />White River. tile bII Ejor tributaries of the Green River. In the mainstem <br />Colorado River. it is currently found from lake Powell extending about 201 miles <br />upstream to Palis~. Colorado. and in the lower 33 miles of the Gunnison River, <br />a tributary to die .instem Colorado River (lyus et al. 1982). Recent <br />investigatiOll'" ~t adult and young-of-year Colorado sQuawfish inhabit the <br />San Juan River is fir upstream as 151. 5 miles above lak.e Powell. <br />