7739 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I 2 Similar to most Colorado River Basin rivers, the fish fauna of the Yampa River is dominated by cyprinids and catostomids. A total of 12 fishes are native to the Yampa River, and at least 20 nonnative fish species have been introduced (fable 1). The upper Yampa River and i~ tnbutaries are typical trout waters, and a transition to cool- or warmwater fishes occurs at lower elevations. Of the native fishes, seven are considered in jeopardy or declining and have federal status under the 1973 Endangered Species Act as amended; four are endangered and three are under review (candidates) for federal listing. Most of the nonnative fishes have established reproducing populations. Fish collections used in our analyses were from the lower 94.1 km (river km) of the Yampa River, between the upper end of Cross Mountain Canyon and the Yampa-Green River confluence (Figure 1). This section of river was divided into five reaches defined mainly by prominent changes in terrain and river morphology (Figures 1, 2). Cross Mountain Canyon (Reach 5) is a high-gradient reach with boulder, cobble, and gravel substrates. Mainchannel habitat is primarily rocky falls, rapids, and runs. Small shoreline pools and eddies occur behind boulders. Reach 4 is a low- to moderate-gradient stretch with cobble, gravel, and sand substrates. Terrain is open and hilly. Mainchannel habitat mostly follows a repetitive run-rime-pool sequence, and shoreline habitat consists primarily of pools and embayments. From the lower end of Lily Park downstream to Deerlodge Park (Reach 3), the Yampa River broadens and slowly meanders through flat, open terrain and braids around sand and gravel bars. Numerous backwaters and shoreline embayments occur in this reach. Substrates are primarily gravel, sand, and silt The lower 72.2 km of the Yampa River are contained within Yampa Canyon. In upper Yampa Canyon (Reach 2), the Yampa River is mostly a high-gradient system of rocky runs and rapids, eddies, and riffles. Boulder, cobble, and gravel substrates predominate. Downstream of Harding Hole to the Yampa-Green River confluence Qower Yampa Canyon, Reach I), channel gradient is mostly low to moderate, and mainchannel habitat consists primarily of deep runs and pools and braided sections interspersed with gravel and cobble bars. In reaches 1 and 2, shoreline habitat is mostly pools, eddies, and embayments. Extent of backwater development is higher in Reach 1 than in Reach 2. MEmODS SampUng The main objective of fish sampling conducted in the lower 94.1 km of the Yampa River during 1980-1984 was to document Colorado squawflSh reproduction through collection of age-O fish. Accordingly, annual sampling schedules were based primarily on knowledge of timing and location of Colorado squawfish spawning in the Upper Colorado River System, particularly the Green River sub-system, and were revised as new information was produced. Vanicek and Kramer (1969) collected adult Colorado squawfish in reproductive condition (ripe) from the Green River, Utah, in late June through early August, 1964-1966. They reported that, in all years, ripe Colorado squawflSh were first collected about 1 month