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18 <br />competitive advantage because of the high flows, which were similar <br />to historical flows in the river segment. Many introduced minnows <br />spawn later than native fishes, and their young-of-the-year (YOY) <br />probably entered winter months at a significantly smaller size than <br />during lower-flow years. The introduction of predaceous largemouth <br />bass, green sunfish, and mosquitofish to the riverine environment <br />could reduce survival of young native fishes, negating their <br />reproductive advantage in higher-flow years. A determination of <br />the long-term effects of the high flow years 1983 and 1984 on fish <br />populations and habitat in the Grand Junction area should be made. <br />Yampa River, 1983 and 1984 <br />On the Yampa River 1983, 711 fish were collected by <br />electrofishing and hook-and-line sampling. Four native and four <br />introduced species were represented along with one hybrid (Table <br />3). In 1984, 1138 fish were collected in August by trammel net and <br />electrofishing. In October, 929 fish were collected by <br />electrofishing. In total, five native and six introduced species <br />were represented along with three hybrids (Table 3). <br />Yampa Canyon, August 2-4, 1984 <br />A total of 87 fish was collected with floating and stationary <br />trammel nets August 2-4, 1984, in Yampa Canyon (Figure 6). Five <br />native and three introduced species were represented. At the <br />intensive site (RMI 19.3-16.3), 57 fish were collected. An <br />additional 30 fish were collected between RMI 13.7 and 8.7. <br />Flannelmouth sucker, channel catfish, roundtail chub, and Colorado <br />squawfish were the most abundant species collected (Figure 6). <br />Colorado squawfish comprised 16 percent of the catch within the