Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon
St. Louis, Missouri, 11-13 January 2005
36. DRIFT DYNAMICS OF LARVAL PALLID STURGEON IN A SIDE CHANNEL OF THE UPPER MISSOURI RIVER, MONTANA.
Patrick J. Braaten*, Columbia Environmental Research Center, Fort Peck Project Office, Fort Peck, Montana 59223; Phone 406-526-3253; Patrick_braaten@usgs.gov
David B. Fuller, Montana Fish, Wildlife and Parks, Fort Peck, Montana 59223; Phone 406-526-3253; firstname.lastname@example.org
The goal of this study was to obtain an understanding of the drift behavior and drift dynamics of larval pallid sturgeon (Scaphirhynchus albus) in the upper Missouri River, Montana. The objectives were to: 1) quantify the vertical drift distribution of larval pallid sturgeon in the water column, 2) determine drift rates of larval pallid sturgeon related to hydraulic conditions and age, and 3) estimate the length of river drifted during ontogenetic development. Larval pallid sturgeon (ages 1, 2, 5, 9, 11-days-old) were released during separate events at the head of a 1,400-m-long side channel of the Missouri River. The larvae were sampled continuously at locations 100-m, 500-m, 900-m, and 1,300-m downstream from the release point with nets positioned in the lower 0.5 m of the water column and in the upper 0.5 m of the water column. All age classes of larval pallid sturgeon were sampled primarily in the lower 0.5 m of the water column indicating a strong tendency to drift near the river bed. The drift rate of larval pallid sturgeon was similar to mean water velocities in the side channel, and the drift rate of larvae varied slightly among ages. Initial models of larval sturgeon transport suggest that the total downstream drift distance of larvae is dependent on water velocity, and that pallid sturgeon may drift in excess of 200 km during the first 11 days of the larval life stage. Inferences from this study provide a possible mechanism to account for the lack of pallid sturgeon recruitment in the upper Missouri River.