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Fish Scale-Loss caused by Simulated Hydraulic Shear Stress

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Dataset Overview

Riverine fishes found within streams impacted by hydropower also often pass through hydropower turbines during annual downstream migrations. During turbine passage events, fish may experience a suite of stressors including rapid pressure changes, impacts from turbine blades, and exposure to hydraulic shear. Scale-loss is often observed in fish collected below dams and hydraulic shear is the most likely cause of this trauma. While exposure to shear may cause other injuries, scale-loss appears to be the most common non-lethal injury observed to date. We sought to quantify how hydraulic shear may cause scale-loss in rainbow trout, gizzard shad, and hybrid striped bass by precisely controlling the exposure level (velocity) and duration (seconds) of a water jet. We targeted the same area for all three species found between the operculum and dorsal fin on the left, lateral surface. Exposure velocities ranged from 0 (controls) to 11.0 meters/second but fish were only exposed to the water jet for 1.5 seconds. A 0.2 milligram/milliliter solution of fluorescein was used to stain the areas of scale-loss by submerging each fish in this solution for at least 6 minutes. Fluorescein was used because it interacts with epithelial tissue that has been damaged and it fluoresces under ultraviolet lighting. Fish were photographed under short- and longwave ultraviolet lighting in a dark chamber to capture fluorescence. Fish photographs were analyzed using ImageJ and the proportion of descaled area was estimated for each fish within a 35 by 35-millimeter square. In general, these data highlight how exposure to hydraulic shear may lead to significant levels of descaling in riverine fishes.