Spawning related movement of shovelnose sturgeon in the Missouri River above Fort Peck Reservoir, Montana

The hypotheses of this study were (i) that shovelnose stur-geon would make upstream movements to spawn, (ii) move-ment of spawning fish would be greater in a year with higher discharge, and (iii) that spawning fish would have greater movements than reproductively inactive fish. Shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque, 1820) in five reproductive categories (e.g. males, confirmed spawning females, potentially spawning females, atretic females, and reproductively inactive females) were tracked in 2008 and 2009. All reproductive categories, except reproductively inac-tive females, exhibited large-scale movements and had omni-directional movements. No differences in movement rates were observed in confirmed spawning females between years despite a 45 % higher peak discharge in 2008 (839 m3 s1) than in 2009 (578 m3 s1). A peak discharge was obtained at a faster rate in 2008 (165 m3 s1 day1) than in 2009 (39 m3 s1 day1), and high discharge was of greater dura-tion in 2008. Reproductively inactive females did not exhibit large-scale movements and their movement rate differed from other reproductive categories. Shovelnose sturgeon spawned in both years, despite highly varying hydrographs between years