Laserfiche WebLink
sturgeon ( Bramblett 1996). According to this study, pallid sturgeon were found most often in sinuous <br />channels with islands or alluvial bars present. Straight channels, and channels with irregular patterns or <br />irregular meanders were only rarely used by pallid sturgeon. Seral stage of islands or bars near pallid u <br />sturgeon was most often subclimax ( Bramblett 1996). 15 r+ol <br />f�t%s 4"a� kL <br />Bramblett (1996) noted that because macrohabitats used by pallid sturgeon were more specific and �—� -- <br />restrictive than shovehlose sturgeon, features in these macrohabitats may be more important to pallid <br />sturgeon than to shovehlose sturgeon. Bramblett (1996) found macrohabitats used by pallid sturgeon m <br />were diverse and dynamic. For example, pallid sturgeon used river reaches with sinuous channel 00 <br />patterns and islands and alluvial bars which generally have more diversity of depths, current velocities, <br />and substrates than do relatively straight channels without islands or alluvial bars. The diversity of <br />channel features such as backwaters and side channels was also higher. The subclimax riparian <br />vegetational seres in these areas are indicative of a dynamic river channel and riparian zone (Johnson <br />1993). <br />In telemetry studies of pallid sturgeon on the middle Mississippi River, Sheehan et al. (1998a) found a <br />positive selection for main channel border and downstream islands tips and also for depositional areas <br />between wingdams and deep holes off wingdam tips. That seems to correlate well with Carlson et al. <br />(1985). Sheehan et al. (1998a) speculated that between wingdam areas and downstream island tips <br />maybe used as velocity refugia and/or feeding stations. Study sturgeon were found most often in main <br />channel habitat, however, they exhibited selection against that habitat type. Their occurrence in such <br />habitat was not surprising considering main channel comprised approximately 65 percent of the <br />available habitat in the study reach (Sheehan et al. 1998a). <br />Constant et al. (1997) reporting on radio - tracked sturgeon, stated that sturgeon were most frequently <br />found in low slope areas and that such areas were used in proportion to their availability. No sturgeon <br />were observed on extremely steep slopes. They found that sand made up over 80 percent of the <br />substrate in low slope areas where over 90 percent of pallid sturgeon were located. Constant et al. <br />(1997) stated that the preference for sand substrates in low slope areas suggests that pallid sturgeon use <br />such areas as current refagia. Sand substrates were found to have lower invertebrate densities than <br />substrates of silt -clay which were generally located on areas of steep slope which were exposed by <br />swift currents. As such, it would have been energetically costly for pallid sturgeon to remain near these <br />substrates for extended periods of time. However, telemetry observations showed 55 percent of <br />sturgeon locations occurred within 10m of steep slopes, suggesting that pallid sturgeon remained near <br />areas of high food abundance (Constant et al. 1997). <br />Some caution must be used in evaluating the results of habitat preference studies conducted in the highly <br />altered river environments of today as there is no way to measure pallid sturgeon preference for habitats <br />that no longer exist (Dr. Robert Sheehan, SIUC, pers. comm.). The results of studies by Bramblett <br />(1996), Constant (1997), and Sheehan et al. (1998a) are indicative of the habitats being used by pallid <br />sturgeon in the altered environment of today. <br />108 Status Range Wide -PS <br />