Evaluation of Fish Injury Mechanisms During Exposure to Turbulent Shear Flow

Development of more fish-friendly hydroelectric facilities requires better understanding of the biological response of juvenile fish when they migrate through the turbines and other downstream passage facilities. Juvenile fall Chinook salmon Oncorhynchus tshawytscha were exposed to turbulent shear flows in a laboratory by using two mechanisms: fast-fish-to-slow-water in which test fish were carried by the fast-moving water of a submerged turbulent jet into the slow-moving water of a flume; slow-fish-to-fast-water mechanism in which fish were actively introduced from standing water into the turbulent water jet through an introduction tube placed just outside the edge of the jet. Sensor Fish devices were also exposed to same conditions as live fish to determine how hydraulic conditions affected fish injury and establish correlation metrics between Sensor Fish device measurements and live fish injuries. Motion-tracking analysis was performed on high-speed, high-resolution digital videos of all the releases at water jet velocities ranging from 3 to 22.9 m/s. Fish responded differently and sustained different injuries when they were subjected to turbulent shear flows under the two exposure mechanisms. Fish acceleration was found to be the most predictive parameter for the observed injuries. Generally, the thresholds for fish injury under the fast-fish-to-slow-water mechanism were higher than those of fish under the slow-fish-to-fast-water mechanism for both minor and major injuries. The 10% probability of major injury corresponded to fish acceleration levels was 673 m/s2 for the fast-fish-to-slow-water mechanism and 340 m/s2 for the slow-fish-to-fast-water mechanism. A 10% probability of major injury threshold was found to occur at Sensor Fish accelerations of 513 and 260 m/s2 for the fast-fish-to-slow-water and slow-fish-to-fast-water scenarios, respectively. This information is applicable to the design and operation of turbines and spillways because these two tested mechanisms simulate the severe hydraulic events fish usually experience during passage at hydropower dams.