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Technologies track, map fish behavior

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February 09, 1999 Share This!

RICHLAND, Wash. — Psychology normally isn't associated with fisheries biology, but the behavior of fish could be an important factor in restoring endangered salmon stocks in the Columbia and Snake rivers.

Scientists at the Department of Energy's Pacific Northwest National Laboratory have developed tools to study how fish behave and to evaluate fish bypass systems at dams. The scientists coupled a multibeam sonar tool with an interactive computer animation program to track juvenile fish as they approach a prototype surface flow bypass recently installed at Bonneville Dam on the Columbia River between Washington and Oregon.

The multibeam sonar tool, called Dual-Head Multibeam Sonar, is a modification of a hydroacoustic device commonly used to map the bottom of oceans. The dual-head sonar nonintrusively tracks a fish's swimming direction and velocity over a large volume of water. Information collected by the multibeam sonar tool is transferred to computer software designed by Pacific Northwest. This software, called MTrack, tracks individual fish and allows for creation of a three-dimensional animation of what took place underwater.

"This is a very sophisticated system," said Robert L. Johnson, Pacific Northwest principal investigator. "These tools allow us to see fish movement more completely and take us one step closer to understanding how fish behave near these test facilities."

The U.S. Army Corps of Engineers, which built and operates Bonneville Dam, is attempting to find the best combination of bypass entrance dimensions, river velocity and flow to allow for safer downstream passage of juvenile salmon. Results from Pacific Northwest's study could be helpful in designing future surface flow bypasses, if that option is pursued as an alternative to passage through turbines.

Using the sonar tool, Pacific Northwest scientists tracked about 15,000 juvenile salmon as they approached the bypass at Bonneville Dam. The scientists discovered the juvenile salmon, also called smolt, tend to work harder as they approach the prototype bypass by swimming against the current, toward the bottom of the bypass and parallel to the bypass structure.

"This complex behavior could be caused by many factors," Johnson said, "such as noise from turbines or the existence of a new structure. While we don't know why the fish act in this manner yet, we now have the ability to develop that understanding by studying smolt behavior in great detail."

Pacific Northwest scientists looked at how fish behavior differed when the prototype bypass entrance was 1.5 meters (five feet) wide and 6.1 meters (20 feet) wide. The study indicated the effort fish exerted to get to the bypass entrance was similar regardless of entrance size.

At Bonneville Dam, Pacific Northwest scientists mounted the dual-head multibeam sonar tool on a platform immediately upstream of the dam. The device transmits sound on the horizontal sonar head while receiving echoes on the horizontal and vertical sonar heads. The sonar tool "pings," or sends out sounds, up to 20 times every second. The combined echoes provide a three-dimensional location of a fish for every "ping."

The echoes are fed into a computer system on land then sent on to a third computer, where the information is combined into files compatible with the MTrack processing software. MTrack uses algorithms to analyze data and translate it into fish positions. The data then can be displayed on an interactive three-dimensional scene graphic that replays fish movement relative to the dam and the prototype bypass.

Since 1996, Pacific Northwest scientists have done similar analysis work at Lower Granite Dam, which is operated by the Corps' Walla Walla District, on the Snake River in southeastern Washington. Scientists are continuing this work for the Corps' Portland District, which operates Bonneville and two other dams on the lower Columbia River. The Corps is gathering information on many possible methods for improving downstream fish passage through dams and their turbines, including surface bypasses.

Tags: Fundamental Science, Operations, Biology, Facilities

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