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Wired 'Salmon' Records how Fish Handle
Rough Ride through Dams

by Amy E. Nevala
Seattle Post-Intelligencer, October 19, 2000

Scientists will use data to help lower mortality rate on the migratory journey

This month 601 salmon will take a survival test, plunging 40 feet down a spillway at Washington's Rock Island Dam. Most will live. A few will perish. And one is going to have a lot to say about it.

Salmon face many obstacles, including the often deadly turbine blades of hydroelectric dams.  So scientist have developed artificial fish laden with sensors to get a close-up view of the dangers. Called a sensor fish, the plastic device resembles a high-tech toilet paper tube stuffed with $5,000 worth of computer chips, batteries and wires. Its mission is to record pressure changes and acceleration as it tumbles through the dam, providing scientists a new view of dams as experienced by hundreds of thousands of migrating chinook, coho, sockeye and steelhead salmon (see graphic).

Ultimately, scientists hope to use the data to create more fish-friendly dams in Washington.

"Before, we either had dead fish or we had live fish and that didn't tell us much," said Robert McDonald, a fisheries biologist for Chelan County's Public Utility District. "This way really paints a picture of what happens to them in the dam."

Biologists with the Department of Energy's Pacific Northwest National Laboratory in Richland will conduct tests over several days later this month near Wenatchee at Rock Island Dam, the oldest and smallest of 15 dams on the main stem of the Columbia River.

"We want to find an operating point that minimizes injury to the fish," said biologist Tom Carlson, manager of Pacific Northwest National Laboratory's sensor fish project.

In the past two decades modifications to dam turbines, which pass most fish through safely but still rip, bruise and kill others in the process, have reduced fish mortality to about 5 percent.

The death rate is even lower for fish passing over waterfall-like dam spillways, about 2 percent. Still, Carlson sees room for improvement.

Sensor fish do not swim. Placed in the water, they just go with the flow, their tiny internal computers measuring and collecting data in the minutes it takes to pass through the dam. Halfway through the ride two airbag-type balloons pop open, floating the sensor fish to the surface so scientists waiting in boats downriver can find them.

Once on board the vessel, a scientist with a computer can attach a cable to the sensor fish and download the data. Acceleration and pressure recordings tell the scientists how fast the fish are moving and what forces, such as turbulence, they experience.

Then they'll compare the data with lab tests and tweak dam designs in a way that reduces injury to the fish, as they are already doing in Oregon.

Pacific Northwest National Laboratory's  first-generation gummy version of the sensor fish Sensor fish runs through the Bonneville Dam showed that fish that slipped through the deepest part of the dam experienced less turbulence, limiting dizziness and subsequent exposure to predators.

"Now that we have information about their routes we can modify the way the water exits in a way that helps the most fish," Carlson said.

Engineers have developed about 25 sensor fish since Pacific Northwest National Laboratory scientists dreamed up the idea three years ago. The first prototypes, 6-inch-long gummy fellows with tails, have been redesigned into today's more durable sensor fish tubes.

Scientists say they want to return to the original fish design, since the idea behind the sensor is to mimic the twists and turns that live, pliable salmon make as they tumble through dams.

About $750,000 has been spent on their development so far. A dozen have been lost and, at $5,000 a head, "every one hurts," Carlson said when describing those demolished in turbines or lost to the Columbia.

On the drawing board are plans to create even higher-tech versions of the sensor fish, including an adult-size version (current models resemble juveniles) with better sensor placement to collect data in way that is most like that experienced by real fish.

"We've got a chance now," said Carlson, "to really see into the salmon world."

Related Links:
Pacific Northwest National Laboratory: Gummy Fish Photo
New York Times: Sensor Fish Brave the Bumps to Tame Dams by Henry Fountain

P-I reporter Amy E. Nevala
Wired 'Salmon' Records how Fish Handle Rough Ride through Dams
Seattle Post-Intelligencer, October 19, 2000

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