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important dietary components (Modde and Schmulbach 1977, Carlson et al. 1985), the occurrence of <br />lake and terrestrial invertebrates in sturgeon stomachs suggest that drifting invertebrates may also be <br />important forage organisms (Modde and Schmulbach 1977, Contant et al. 1997). Aquatic <br />invertebrates (principally the immature stages of insects) compose most of the diet of shovelnose <br />sturgeon, while adult pallid sturgeon and presumed hybrids consume a greater proportion of fish (mostly <br />cyprinids). Other researchers also reported a higher incidence of fish in the diet of adult pallid sturgeon "n,�nows <br />than in the diet of shovelnose sturgeon (Cross 1967; Held 1969). Most piscivorous Missouri River 1117 C", f s. <br />species eat large quantities of aquatic insect larvae in early life and even as adults (Modde and <br />Schmulbach 1977). <br />A large pallid sturgeon adult and numerous shovehose sturgeon were observed on video tape feeding <br />in relatively clear water in the tailrace of Ft. Peck Dam on the Missouri River in Montana. The large <br />adult pallid sturgeon "stood on its fins" in a stationary position. That would allow food organisms to <br />wash into its mouth with the current beneath it (Steve Krentz, pers. comm. 1994). During April of <br />1999, adult pallid sturgeon were collected near the mouth of the Yellowstone River. Several adult <br />pallid sturgeon were observed with larger ( >6 in)(15 cm) food items distending the abdomen. Upon <br />closer examination, one of the pallid sturgeon was observed with a 9 -in (22 cm) goldeye protruding into <br />the mouth ( Krentz, pers. comm. 1999). <br />Range Wide Distribution and Abundance of Habitat <br />The historic habitat of the pallid sturgeon extended from Montana throughout the Missouri River <br />downstream to the Mississippi River and downstream to the Gulf of Mexico. The lower ends of the <br />larger tributaries also provided suitable habitat for certain times of the season. The total length of the <br />pallid sturgeon range was 3,515 mi (5,656 km). <br />Currently, the Missouri River (1,154 mi) (1,857 km) has been modified significantly with approximately <br />36 percent of the riverine habitat inundated by reservoirs, 40 percent channelized, and the remaining 24 <br />percent altered due to dam operations (USFWS 1993). Most of the major tributaries of the Missouri <br />and Mississippi Rivers have also been altered to various degrees by dams, water depletions, <br />channelization and riparian corridor modifications. <br />The middle Mississippi River from the mouth of the Missouri River to the mouth of the Ohio River is <br />principally channelized with few remaining secondary channels, sandbars, islands and abandoned <br />channels. The middle Mississippi River has been extensively diked to maintain a 9 ft (2.7 m) ( <br />navigation channel and flood control levees have reduced the size of the floodplain by 39 percent. <br />The lower Mississippi from the Ohio River to near the Gulf have eliminated major natural floodways <br />and reduced the land area of the floodplain by more than 90 percent (Fremling et al. 1989). Fremling <br />et al. (1989) also reports that levee construction isolated many floodplain lakes and raised river banks. <br />As a result of levee construction, 15 meander loops were severed between 1933 and 1942. <br />Status Range Wide -PS 111 <br />