September 1, 2016.
Hydropower dams are used throughout the world to generate electricity and dams can negatively affect fish, as they can hinder or block migration or be a source of injury and mortality during passage. When moving downstream, fish can pass through the turbines instead of other routes (e.g. spillway and juvenile bypass system)where there is a sudden decrease in pressure that can cause barotraumas, injuries from the changes in barometric pressure, (e.g., hemorrhaging, embolism, ruptured organs) due to internal gases expanding. To determine the response of American eels, Anguilla rostrate, to rapid decompression, testing was conducted in the Mobile Aquatic Barotrauma Laboratory (MABL) at PNNL’s Aquatic Research Lab between 6 June and 5 August 2016. In total, 105 eels were tested in MABL’s hyper/hypobaric chambers by simulating the rapid decompression experienced in turbines. Eels were acclimated to 25 feet depth and the nadir, lowest pressure the eels experienced, during the test was measured. This was done to determine the ratio of pressure change (RPC) the eels experienced during testing (i.e., acclimation pressure/nadir pressure). After exposure, the eels were held for two days to monitor survival before a necropsy was performed. There were only two mortalities observed (1.9%) in the study. Twenty-one fish were found to have non-fatal barotraumas. However, these injuries are fatal for other species (e.g., Chinook salmon). The maximum RPC for fish with injuries was 11.32, while the greatest RPC in the study was 19.66, and so further research is needed to determine if there is a RPC that will result in 100% mortality for this species. The results provide information that can be used in the design and operation of turbines to minimize mortality for fish that pass through.
Terrestrial and Aquatic Ecology
Pacific Northwest National Laboratory (PNNL)
*This project has been made possible with support from Chevron (www.chevron.com) and the California State University STEM Teacher Researcher Program. Funding was provided by the U.S. Department of Energy, Water Power Program.