Consequences of a drying reservoir: Positive or negative effects on riverine fish?

The article examines the ecological consequences of reservoir drying on riverine fish movement and assemblages, focusing on Pearce Ferry Rapid formed by the recession of Lake Mead on the Colorado River, USA. This newly emerged hydraulic barrier appears to restrict upstream movement of native fish species such as Razorback Sucker (Xyrauchen texanus) and Flannelmouth Sucker (Catostomus latipinnis), while effectively blocking nonnative fish species from accessing native fish habitats in western Grand Canyon. Fish community analyses revealed native fish dominance upstream of the rapid and nonnative dominance downstream, with limited upstream passage detected primarily before the rapid's full development. The study highlights Pearce Ferry Rapid's potential role as a natural barrier benefiting native fish conservation by limiting invasive species spread, but also notes possible negative impacts on native fish connectivity and management implications amid ongoing reservoir level declines.