SummaryThe hypotheses of this study were (i) that shovelnose sturgeon would make upstream movements to spawn, (ii) movement 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 inactive females, exhibited large-scale movements and had omnidirectional movements. No differences in movement rates were observed in confirmed spawning females between years despite a 45% higher peak discharge
Sudden changes in water releases below hydropower facilities (hydropeaking) can dramatically affect benthic organisms. Aquatic gastropods are an ideal organism for studying such effects because they inhabit littoral areas that are frequently dewatered during hydropeaking and have a low dispersal ability making them highly susceptible. We explored mortality rates of Taylorconcha serpenticola, the threatened Bliss Rapids snail, in four laboratory experiments that simulated hydropeaking during varying seasons and varying hydropower operation scenarios. Experiments were conducted in a light and temperature controlled Conviron® and were designed to simulate conditions on the Middle Snake River, Idaho, USA, in reaches that are subjected to hydropeaking. Experiments examined the effects of three air temperatures (winter = −7°C, spring = 17°C and summer = 37°C), three durations of exposure to air (2, 4 and 6 h), three dewatering rates (instantaneous, 0.3 and 0.15 m h−1), two substrate textures (smooth and vesicular) and consecutive daily exposures (1 to 15 days). With 2 h exposures >80% of gastropods survived under both the summer and winter condition, but with 6 h exposure only 60% survived under winter conditions and almost none survived under summer conditions. Survivorship of gastropods was always high under spring conditions (>90%) even when exposed for 6 h d−1for up to 15 days. When subjected to consecutive daily exposures, survivorship was lowest under winter conditions. Neither rate of dewatering nor substrate texture affected survivorship. Our data suggest that hydropower operations that include rapid stage fluctuations under extreme temperatures can cause high mortality of sensitive benthic species especially when exposure time is prolonged. Future water management policy decisions will need to consider these factors to manage for protection of aquatic species of conservation concern. Copyright © 2013 John Wiley & Sons, Ltd.
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