Mortal injury of juvenile Chinook salmon during hydroturbine passage: Implications for hydroturbine operation and design

Passage of fish through hydroturbines occurs globally. This is of particular importance for dams that are located in waters where migratory fish species exist. Within the Snake and Columbia Rivers, thousands of salmonids pass through hydroelectric dams during annual seaward migration. A proportion of these fish will pass through hydroturbines. A number of misconceptions with this passage exist, including the rate of contact related mortality associated with turbine blades. However, all fish are subjected to varied decompression and may sustain injuries related to barotrauma. We examined this interaction using Chinook salmon (Oncorhynchus tshawytscha) in a laboratory setting. Juvenile fish were acclimated to a range of depths and subsequently exposed to simulated turbine passage. These simulations exposed fish to rapid changes in pressure between 6.89 to 413.68 kPa (1 to 60 PSI) using computer controlled hyper/hypobaric chambers. Rates of mortal injury were a function of acclimation depth (pressure equivalent) and exposure pressures. The relationships between barotrauma and pressure exposure can be used to guide turbine operations and turbine design globally.