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.for areas with dune -like bottom contour. Studies conducted in the Atchafalaya River found <br />similar use of areas of undulating bottom contour, and suggested pallid sturgeon use such <br />areas as current refugia (Constant et al. 1997). <br />Studies conducted in the middle Mississippi River by Hurley (1999) found 15 radio - tagged <br />pallid sturgeon exhibited positive selection in relation to their availability for main channel <br />border habitats, downstream island tips, areas between wing dams, and wing dam tips. He <br />found negative selection in relation to availability for the main channel, areas above wing <br />dams, and areas below wing dams. Preliminary findings in lower Platte River studies also <br />show substantial use of downstream edges of alluvial bars. Habitats frequently used were <br />generally characterized by sharp changes in depth. Study fish were found to use the same <br />length of bar edge repeatedly, and stay in this type of habitat for several weeks at a time (E. <br />Peters, University of Nebraska - Lincoln, personnal communication). <br />Pallid sturgeon are most frequently caught over a sand bottom which is the predominant <br />bottom substrate within its range on the Missouri and Mississippi rivers. Twenty -four pallid <br />sturgeon in the Yellowstone and Missouri rivers in Montana and North Dakota were found <br />most often over fines and sand (92.8 percent of the time) and appeared to avoid gravel and <br />rubble ( Bramblett 1996). Studies performed in the Atchafalaya River (Constant et al. 1997), <br />and preliminary findings in the lower Platte (E. Peters, University of Nebraska - Lincoln, <br />personal communication), have both found similar primary use of sand substrate. <br />Findings from a study on the Missouri River in South Dakota indicate that pallid sturgeon <br />used a wide range of bottom current velocities with small pallid sturgeon utilizing areas of <br />higher current velocities (30 -50 cm/s) and larger pallid sturgeon using areas of lower current <br />(5 -25 cm/s). Pallid sturgeon did not use backwater or off channel areas in this reach <br />(Erickson 1992). Other studies in Montana found they were most frequently associated with <br />water velocities ranging from 1.3 to 3.0 fps (FWS 199' )). These velocities are common <br />throughout the range of the pallid sturgeon. Pallid sturgeon collected from the Missouri <br />River upstream from Garrison Reservoir in North Dakota during the spring and fall of 1998 <br />to 1991 were found in deep pools at the downstream end of chutes and sandbars, and in the <br />slower currents of near shore areas. Bramblett (1996) reported pallid sturgeon were found <br />using bottom velocities from 0.43 to 4.4 fps in the Yellowstone River, from 0 to 2.3 fps on <br />the upper Missouri River, and from 0 to 4.6 fps in the lower Missouri River. Ongoing studies <br />in the lower Platte River have found pallid sturgeon primarily using bottom velocities from 0 <br />to 0.7 m/s (E. Peters, University of Nebraska - Lincoln, personal communication). <br />In the Missouri and Yellowstone rivers, pallid sturgeon have been found in water depths <br />ranging from 3.3 to 47.4 feet. Ongoing lower Platte River studies have found pallid sturgeon <br />generally using depths from 1 to 4 feet. (E. Peters, University of Nebraska - Lincoln, personal <br />communication). <br />There is little information to indicate temperature preference or the direct effects of <br />7 <br />