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<br />0009i1/, <br /> <br />. <br /> <br />FORAGE FISH <br /> <br />Maintenance of the river aquatic system and fishery is dependent <br />on the hydro-periods of a year-round flow regime. Explanations <br />of the importance of the hydrocycle to fisheries have been <br />amplified by Crance (1988), Junk et al. (1989), and Hill et al. <br />(1991), among others. Our present ability to prescribe the full <br />range of specific flows for Platte River hydro-periods is <br />limited, however. For the purposes of Task 5, this discussion is <br />confined to base flow targets needed to protect aquatic resources <br />used by endangered species. Base flows support not only the <br />fishery, but provide protection to sandbar nesting least terns <br />and piping plovers and may help sustain wet meadow productivity. <br /> <br />The recommended target flow should be provided throughout the <br />central Platte River and should therefore be measured at the four <br />USGS gaging stations (Overton, Odessa, Kearney, and Grand Island) <br />located within this reach of the river. <br /> <br />Species habitat models are tools used by decision makers, water <br />users, and habitat managers to analyze impacts of both past and <br />future projects and to help make resource management decisions. <br />The model that is chosen to determine a target flow for forage <br />fish must be capable of addressing both the diversity and <br />abundance of fish species that are found in the Platte River. <br />The procedures used to calculate habitat target flows for forage <br />fish should be designed to "identify conditions to provide an <br />adequate riverine environment to sustain the maximum diversity <br />and abundance of forage fishes needed to support the recovery <br />goals of endangered species" (Biology Workgroup 1990). A diverse <br />assemblage of fish species is needed to maintain the integrity of <br />the fishery for the interior least tern, and bald eagle (and some <br />30 other non-listed piscivorous migratory bird species that use <br />the Platte River). <br /> <br />A flow recommendation for forage fish should not be based solely <br />on physical microhabitat variables (i.e., depth, velocity, <br />substrate, and cover). The recommendation also should consider <br />the relationship between flows and specialized habitats, and <br />macrohabitat variables such as water temperature. <br /> <br />Sinqle soecies aooroach <br /> <br />A workshop to develop suitability curves for forage fish in the <br />Platte River system was held in July 1986 with species experts. <br />The thrust of this workshop and the species experts' work was to <br />select a single species which had habitat requirements adequate <br />to support all other forage fish in the River (Fannin and Nelson, <br />1986). This "single-species" approach encumbers a single set of <br />Habitat Suitability Index (HSI) curves to be equally applicable <br />to all diverse habitats of the river (i.e., edges, backwaters, <br /> <br />7 <br />