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fish utilizing seines, benthic trawls and fyke nets. In processing 9855 of these fish, 1 confirmed and 2 <br />probable larval pallid sturgeon have been identified (Joanne Grady, USFWS, pers. comm.). Those <br />data suggest that spawning success and larval sturgeon abundance are low. <br />Habitat and Food Requirements <br />Habitat Characteristics - Forbes and Richardson (1905), Schmulbach et al. (1975), Kallemeyn <br />(1983), and Gilbraith et al. (1988) describe pallid sturgeon as being a fish well adapted to life on the <br />bottom in swift waters of large, turbid, free - flowing rivers. Pallid sturgeon evolved in the diverse <br />environments of the Missouri and Mississippi Rivers. Floodplains, backwaters, chutes, sloughs, islands, <br />sandbars, and main channel waters formed the large -river ecosystem that provided macrohabitat <br />requirements for pallid sturgeon and other native large -river fish. Those habitats were historically in a <br />constant state of change. Mayden and Kuhajda (1997) describe the natural habitats to which the pallid <br />sturgeon is adapted as: braided channels, irregular flow patterns, flooding of terrestrial habitats, <br />extensive microhabitat diversity and turbid waters. Today, those habitats and much of the once <br />functioning ecosystem of the pallid sturgeon has been changed by human developments. <br />The historic floodplain habitat of the Missouri and Mississippi Rivers provided important functions for <br />the native large -river fish. When floodflows crested the river's banks, floodplains provided the major <br />source of organic matter, sediments and woody debris for the main stem rivers when floodflows crested <br />the river's banks. The transition zone between the vegetated floodplain and the main channel included ,C <br />habitats with varied depths described as chutes, sloughs, or side channels. The chutes or sloughs <br />5 between the islands and shore were shallower and had less current than the main channel. Those areas <br />, provided valuable diversity to the fish habitat and probably served as nursery and feeding areas for <br />many aquatic species (Funk and Robinson 1974). The still waters in this transition zone allowed <br />organic matter accumulations, important to macroinvertebrate production. Both shovelnose sturgeon <br />KX and pallid sturgeon have a high incidence of aquatic invertebrates in their diet (Carlson et al. 1985; <br />GJ Gardner and Stewart 1987). Floodflows connected these important ha�ts d a llowed fish from the <br />main channel to use those habitats to exploit available food sources. , " ;h V" <br />Carlson et al. (1985) captured both pallid sturgeon and shovelnose sturgeon in gear -sets along <br />sandbars on the inside of riverbends, and in deeply scoured pools behind wing dams, indicating overlap <br />of habitat use by the two species. However, 4 of 11 pallids were captured in gear -sets in swifter <br />currents where shovelnose sturgeon were less numerous. Although pallid sturgeon and shovelnose <br />sturgeon habitat use and movements are similar in certain aspects, important differences were noted by p <br />Bramblett (1996). Pallid sturgeon showed significant preferences during most times of the year for <br />sandy substrates, particularly sand dunes, and avoided gravel and cobble substrate preferred for d <br />spawning ( Bramblett 1996). In contrast, shovelnose sturgeon significantly preferred gravel and cobble <br />substrates and avoided sand. S <br />Pallid sturgeon were also more specific and restrictive in use of macrohabitat selection than shovelnose <br />Status Range Wide -PS 107 <br />