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<br />Insects (mostly aquatic forms) were a principal part of the diet for all fishes except <br /> <br />fathead minnow and bluehead sucker. Of the identifiable aquatic insects, immature <br /> <br /> <br />dipterans (especially larval midges, i.e., ceratopogonids and particularly chironomids) <br /> <br />predominated in digestive tracts. Larval chironomids represented at least 21 genera, but <br /> <br /> <br />most were Chironomus followed by Rheotanvtarsus, Eukiefferiella, Polvpedilum, Tanvtarsus, <br /> <br />Cricotopus, and Micropsectra. Representative families of other immature dipterans were <br /> <br /> <br />Simuliidae, Dolichopodidae, Empididae, Muscidae, and Tipulidae. Proportional contribution <br /> <br /> <br />of immature dipterans to diets of red shiner, sand shiner, speckled dace, and flannelmouth <br /> <br /> <br />sucker was higher in the lower than upper reach. Relative importance of immature <br /> <br />dipterans in diets of red shiner, sand shiner, and speckled dace decreased and utilization of <br /> <br />other insects increased as fish length increased. Conversely, relative importance of <br /> <br />immature dipterans in diets of Colorado squawfish and channel catfish increased or <br /> <br /> <br />remained high as fish length increased. Water boatmen (Corixidae), larvae and adults of <br /> <br /> <br />aquatic beetles (predominant taxa were Dytiscidae, Elmidae, Haliplidae, and Hydrophidae), <br /> <br /> <br />caddisfly larvae (mainly Hydropsychidae and Hydroptilidae), or mayfly nymphs (predominant <br /> <br />taxa were Baetidae and Heptageniidae) were minor components of diets for all fishes <br /> <br /> <br />(< 10% of food volume) except larger red shiner, speckled dace, and green sunfish. <br /> <br /> <br />Red shiner and sand shiner ate more semi-aquatic or terrestrial insects than the <br /> <br /> <br />other fishes. Semi-aquatic insects consumed were primarily larval and adult beetles <br /> <br />(predominant taxa were Heterocercidae and Staphylinidae) and adults of the family <br /> <br />Scelionidae (Hymenoptera). Terrestrial insects consumed were primarily hemipterans and <br /> <br />ants. <br /> <br />All fishes ate zooplankton, but it was particularly important in diets of Colorado <br />squawfish < 31 mm TL (especially < 21 mm TL), green sunfish < 31 mm TL, and, to a <br /> <br />8 <br />