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<br />'~~ <br />::) <br />~A' <br />"'"" <br />~.c::. <br />I-' <br /> <br />the squawfish and razorback. Federal and State agencies continue to <br />participate in the raising and stocking of some 5almonid species, though trout <br />are not considered to be a direct competitor. The States have also stocked <br />other nonnative fish in the upper Colorado River including catfish, bass and <br />pike. Fisherman too have transplanted warmwater exotics such as crappie to <br />other rivers within the Upper Colorado River Basin. Though difficult to fully <br />assess. competition with, and predation from, nonnative species has played a <br />role in the decline of these rare fishes, particularly for the 5quawfish and <br />razorback sucker. Nonnative fishes directly or indirectly compete with native <br />species for available resources, such as food and space. The northern pike, <br />for example, appears to occupy a similar niche as the squawfish in the upper <br />Green River. Channel catfish, fathead minnow. various shiners. largemouth <br />bass, and the green sunfish may also compete for habitat. Data indicate <br />direct competition between young squawfish and the redside shiner in nursery <br />areas. and predation from largemouth bass and green sunfish upon young <br />Colorado squawfish is also documented. Predation on razorback eggs and larvae <br />by carp and other warmwater fishes has also been documented (USFWS. 1987). <br /> <br />Backwaters, the same habitat type important to young-of-the-year and juvenile <br />squawfi5h, are often dominated by nonnative species. These nonnative fishes <br />also thrive in gravel pit ponds, manmade side channels. etc., where water is <br />warmer and food is more abundant, the same attributes that attract young <br />squawfish. When these resources are limited. predation and competition <br />result. <br /> <br />3.5.1 Control of Nonnative Fish <br /> <br />Management of river flows may prove to be a useful method to provide an <br />advantage to native species. For example, during the flow years of 1983 and <br />1984, native fishes in the Green and Yampa Rivers reproduced successfully, <br />while nonnative reproduction appeared to be reduced from previous years. <br /> <br />Stocking of most introduced species has been greatly reduced in recent years. <br />Further curtailment of stocking and reduction or elimination of some nonnative <br />species have also been suggested as options to reduce some negative impacts to <br /> <br />25 <br />