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discharge to fluctuate widely during spring spawning, the density of drifting larvae was lower, and when <br />annual runoff volume was highest, paddlefish larval density was highest. Hesse and Mestl (1987) also <br />modeled these same two indices of discharge from Fort Randall Dam with an index of year -class <br />strength. They demonstrated significant negative relationships between artificial flow fluctuations in the <br />spring and poor year -class development for several native and introduced fish species; river carpsucker <br />(Carpiodes carpio), shorthead redhorse (Moxostoma macrolepidotum), channel catfish (Ictalurus <br />punctatus), flathead catfish (Pylodictis olivaris), sauger (Stizostedion canadense), smallmouth <br />buffalo (Ictiobus bubalus), and bigmouth buffalo (I. cyprinellus). The sample size of sturgeon <br />was too small to model in that study; however, a clear relationship existed between poor year -class <br />development in most native species studied and the artificial hydrograph. <br />Modde and Schmulbach (1973) found that during periods of low dam releases, the secondary <br />subsidiary channels, which normally feed into the river channel, become exposed to the atmosphere and <br />thus cease to contribute littoral benthic organisms into the drift. Schmulbach (1974) states that use of <br />sandbar habitats were second only to cattail marsh habitats as nursery grounds for immature fishes of <br />many species. <br />In spite of efforts to constrict and control the Missouri and Mississippi Rivers with reservoirs, stabilized <br />banks, jetties, dikes, levees and revetments, remnant reaches of the Missouri River and the Mississippi <br />River from the Missouri River confluence to the Gulf of Mexico still provide habitat usable by pallid <br />sturgeon. <br />The upper ends of the reservoirs in the upper basin may be influencing the recruitment of larval <br />sturgeon. Both the shovelnose and pallid sturgeon larvaes have a propensity to drift after hatching <br />(Kynard et al. 1998a,b). Bramblett (1996) found that the pallid sturgeon may be spawning in the <br />Yellowstone River between RM 9 and 20 upriver and that from historic catch records, there is some <br />evidence to indicate that the occurrence of pallid sturgeon catches coincide with the spring spawning at <br />the mouth of the Tongue River (Krentz, pers. comm.). Shovelnose sturgeon have been found to spawn <br />in the tributaries of the Yellowstone River as well as such areas as the Marias, Teton, Powder and <br />Tongue Rivers (Gardner, Montana Fish, Wildlife and Parks, pers. comm.) (Annear, Wyoming Fish and <br />Game Department, pers. comm.). Shovelnose sturgeon are successfully recruiting and reproducing in <br />the river stretches in the upper basin and this may be directly related to the amount of larval and juvenile <br />habitat they have available downstream of the spawning sites. Early indications in culturing pallid <br />sturgeon indicate that sturgeon larvae will not survive in a silty substrate. In 1998, most of the larval <br />sturgeon held in tanks at Gavins Point NFH in Yankton, SD, experienced a high mortality when the <br />water supply contained a large amount of silt which settled on the bottom of the tanks. Migration routes <br />to spawning sites on the lower Yellowstone River have been fragmented by low head dams used for <br />water supply intakes. This has forced pallid sturgeon to spawn closer to reservoir habitats and reduced <br />the distance larval sturgeon can drift after hatching. <br />Commercial Harvest - Historically, pallid, shovelnose, and lake sturgeon were commercially <br />Status Range Wide -PS 113 <br />