Laserfiche WebLink
<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Diet was determined for approximately 25% of all razorback sucker larvae 11-18 mm TL <br />collected by light traps. Data were stratified according to fish length (l-mm TL intervals) by year <br />within each river section. The numbers of larvae per TL interval selected for diet analysis from <br />each collection were generally representative of the size composition of razorback suckers in the <br />collection. Each digestive tract (from esophagus to vent) was removed, opened, and qualitatively <br />assessed for percent fullness. Food items were identified, grouped into 11 family, order, or <br />broader-based categories, and a qualitative estimate was made ofthe percentage contributed by <br />each food category to the total volume of food in each digestive tract (Muth and Snyder 1995). <br />The diet measure calculated for each subset was mean percentage each food category contributed <br />to the total volume of food in each digestive tract (Wallace 1981). <br /> <br />RESULTS <br /> <br />Fish Assemblages <br /> <br />Over all years, 53,750 fish representing six families and 16 species were recorded from <br />853 light-trap, 142 drift-net, 80 seine, and 2 dip-net collections in the middle Green River, and <br />59,220 fish representing five families and 15 species were recorded from 650 light-trap and 224 <br />seine collections in the lower Green River (Tables I and 2). All fish collected were larvae, early <br />juveniles, or small adults. Three families and 13 species were common to both river sections, <br />and numbers of captured fish were dominated by three native catostomids (bluehead sucker <br />Catostomus discobolus, flannelmouth sucker C. latipinnis, and razorback sucker) and by <br />nonnative cyprinids (primarily red shiner Cyprinella lutrensis, sand shiner Notropis stramineus, <br />and fathead minnow Pimephales promelas). Native catostomids (including unidentified suckers <br />too damaged or intermediate in diagnostic characters for species identification but assumed to be <br />mostly natives) and nonnative cyprinids, respectively, accounted for 57 and 42% ofthe total <br />catch for the middle Green River, and 7 and 92% of the total catch for the lower Green River. Of <br />the 30,558 native catostomids captured from the middle Green River, 46% were bluehead <br />suckers, 46% were flannelmouth suckers, 6% were razorback suckers, and 2% were unidentified <br />specimens. In the lower Green River, 9% of the 3,546 native catostomids collected were <br /> <br />11 <br />