PNNL

Abstract

Little is known about the 3D depth distributions of individually marked fish in rivers that are in close proximity to hydropower facilities. Knowledge about the depth distributions as fish approach dams can be used to understand how vulnerable fish are to barotrauma. It is necessary to understand fish behavior in forebays subject to naturally buoyance condition when approaching turbines, which is critical for predicting possibility of barotrauma injury caused by pressure change during turbine passage. With the help of Juvenile Salmon Acoustic Telemetry System (JSATS), an innovative and guiding study was conducted using high-resolution 3D tracking results to investigate the depth distributions of subyearling and yearling Chinook salmon and juvenile steelhead tagged with acoustic transmitters passing two dams on the Snake River, Washington State. Several approaches were evaluated to describe the depth fish acclimated. Statistical analysis was performed to large data sets extracted from approximatly 28,000 fish in 2012 and 2013. Our study identified patterns of depth distributions of juvenile fish in the forebays prior to passage through turbines or juvenile bypass systems (JBS). This research indicates that the median depth at which juvenile salmonids are approaching turbines ranges from 2.8 – 12.2m, with the depths varying by species / life history, year, location (which dam) and diel perid (between day and night). One of the most outstanding findings was the difference in dam passage associated with the diel period. The amount of time it took turbine-passed fish to pass the forebay receiving array and enter the powerhouse was much lower during the night than during the day. This research will allow scientists and researchers to understand turbine passage survival in a more concrete manner and conduct research with a better understanding of fish behavior.