Injury and Mortality of Juvenile Salmon Entrained in a Submerged Jet Entering Still Water

Abstract

AbstractDevelopment of more eco‐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 a fast‐fish‐to‐slow‐water mechanism in which test fish were carried by the fast‐moving water of a submerged turbulent jet into the slow‐moving water of a flume. Fish were released at six nozzle velocities: 6.1 (reference control), 12.2, 15.2, 18.3, 21.3, and 22.9 m/s. The onset of minor and major injuries occurred at 15.2 and 21.3 m/s, respectively. The acceleration magnitude threshold (m/s2) of major injury for the fast‐fish‐to‐slow‐water mechanism in this study was found to be significantly higher than that for a slow‐fish‐to‐fast‐water mechanism used in a previous study in which test fish were introduced into a turbulent jet from slow‐moving water through an introduction tube placed just outside the edge of the jet. Fish responded differently and sustained different injuries when they were subjected to turbulent shear flows under the two exposure mechanisms. 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.