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Turbidity <br />Pallid sturgeon historically occupied turbid river systems (Bailey and Cross 1954). <br />Turbidity levels where pallid sturgeon have been found in South Dakota ranged from <br />31.3 to 137 nephelometric turbidity units (NTU) (FWS 1993). In the Yellowstone and <br />Missouri Rivers in Montana and North Dakota, the mean Secchi disc depth was 7.8 <br />inches (20 cm) at 115 pallid sturgeon locations (Bramblett 1996). Turbidity levels ranged <br />from 12 to >100 Jackson turbidity units at pallid sturgeon relocation sites below Fort <br />Peck dam on the Missouri River. Two pallid sturgeons were monitored for habitat use, <br />and both reportedly appeared to prefer turbid water, as relocations in the vicinity of the <br />confluence with the Milk River were consistently in the plume of turbidity along the <br />north bank where the Milk River entered the Missouri River (Bramblett 1996). <br />Turbidity levels at locations of a wild caught pallid sturgeon the lower Platte River <br />ranged from 55 to 315 NTU using a Hach Turbidimeter (Peters et al. 2001). <br />Temperature <br />Water temperature at pallid sturgeon locations in the Yellowstone and Missouri Rivers in <br />Montana and North Dakota ranged from 3.0 to 26.0 °C, with a mean water temperature of <br />15.8 °C (Bramblett 1996). <br />Temperature was measured over radio - tagged pallid sturgeons in the lower Platte River <br />from May 18 to October 8, 1998 and from April 28 to October 5, 1999. Water <br />temperature ranged from 13.1 to 33.7 °C (mean 24.8 °C, median 26.2 °C) in 1998. In 1999 <br />water temperature ranged from 11.4 °C to 30.9 °C (mean 20.6 °C, median 19.8 °C) (Snook <br />2001). <br />Temperatures over the wild caught radio - tagged pallid sturgeon on the lower Platte River <br />were measured and recorded from May 2001 through June 2001, and ranged from 14.8 °C <br />to 24.9 °C (Peters et al. 2001). <br />Because shovelnose sturgeon and pallid sturgeon are known to hybridize, it is likely that <br />spawning habitat requirements are similar ( Hopfar 1997). Shovelnose sturgeon spawn <br />when water temperatures are between 14 and 21 °C (Holland and Huston 1983 in Hopfar <br />1997). <br />Draft Baseline Report — Pallid Sturgeon Section 11 <br />