WSP11191 - Laserfiche WebLink

Home Browse Search

5 with the construction of dams and reservoirs between the 1930's and the 1960's, introduction of nonnative fishes, and removal of water from the Colorado River system. Behnke and Benson (19B3) summarized the decline of the natural ecosystem. They pointed out that dams. impoundments, and water use practices are probably the major reasons for drastically modified natural river flows and channel characteristics in the Colorado River Basin. Dams on the main stem have essentially segmented the river system, blocking Colorado squawfish spawning migrations and drastically changing river characteristics, especially flows and.temperatures. In addition. major changes in species composition have occurred due to the introduction of nonnative fishes, many of which have thrived as a result of changes in the natural riverine system (i.e., flow and temperature regimes). The decline of endemic Colorado River fishes seems to be at least partially related to competition or other behavioral interactions with nonnative species. which have perhaps been exacerbated by alterations in the natural fluvial environment. The Colorado squawfish currently occupies about 1.030 river miles in the Colorado River system (25 percent of its original range) and is presently found only in the Upper Basin above Glen Canyon Dam. It inhabits about 350 miles of the main stem Green River from its mouth to the mouth of the Yampa River. Its range also extends 160 miles up the Yampa River and 104 miles up the White River. the two major tributaries of the Green River. In the main stem Colorado River, it is currently found from Lake Powell extending about 201 miles upstream to Palisade, Colorado (Tyus et al. 1982). and in the lower 60 miles of the Gunnison River. a tributary to the main stem Colorado River (8urdick 1995). Critical Habitat Critical habitat has been designated within the 100-year floodplain of the Colorado squawfish's historical range in the following sections of the Upper 8asin (59 F.R. 13374). Colorado Moffat County. The Yampa River and its 100-year f100dplain from the State Highway 394 bridge in T. 6 N.. R. 91 W.. section 1 (6th Principal Meridian) to the confluence with the Green River in T. 7 N., R. 103 W., section 28 (6th Principal Meridian). Utah. Uintah. Carbon Grand. Emery Wavne. and San Juan Counties: and Colorado. Moffat Countv. The Green River and its 100-year floodplain from the confluence with the Yampa Rlver in T. 7 N.. R. 103 W.. section 28 (6th Principal Meridian) to the confluence with the Colorado River in T. 30 S.. R. 19 E., section 7 (Salt Lake Meridian).