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<br />Of the native fishes, Colorado pikeminnow were usually the most abundant in the lower <br />section. In the upper section, native fish relative abundance was more variable. Native fishes, <br />mostly bluehead sucker (Catostomus discobolus), flannelmouth sucker (Catostomus latipinnis) ~ <br />and speckled dace (Rhinichthys osculus), reached their highest density in the summer of 1993 in <br />both sections. Native fishes were most abundant in early summer, soon after reproduction <br />occurred. Native fish abundance declined by fall perhaps from mortality or changes in habitat <br />use, while the non-native cyprinid abundance increased in the fall due to continued reproduction <br />throughout the summer. <br /> <br />The density (#fish/100 m2) of Colorado pikeminnow was usually highest in the summer, <br />declining in fall, and lowest the next spring. However in 1993 and 1995 summer catch rates were <br />lower than fall, because the summer sampling period anticipated the full presence of Colorado <br />pikerninnow YOY in the backwaters due to delayed reproductive activity in those years <br />(Trammell and Chart 1998 draft) (Table 3 and 4). The density (#fish/100 m2) ofnon-native ~ <br />cyprinids was usually highest in the fall, due to reproduction throughout the summers. <br />The average total lengths (mm) of Colorado pikeminnow YOY collected during the <br />summer occasions ranged from 12.0 to 22.2 mm. Average total length in the fall ranged from <br />31.6 to 50.7 mrn, and in the spring, the range was 25 to 80.2 mm. All of the lowest values were <br />seen in the 1995 year class, and all of the highest in the 1994 year class. Total lengths were ~ <br />pooled for the upper and lower sections, and are shown in Table 3. <br /> <br /> <br /> <br /> <br /> <br />4 <br />