Why these remarkable fish matter to the Northwest
Mechanical fish developed in Richland have made their way through dams from Ice Harbor near Pasco to the Mekong River in Southeast Asia.
Now hundreds more are expected to be deployed around the world, thanks to an agreement to commercialize the technology developed at Pacific Northwest National Laboratory.
The fish are just 3.5 inches long, about the size of a larger salmon smolt.
But they are packed with instrumentation that can give scientists, and now dams and other hydro facility operators, an idea of what passing through dams is like for fish.
The Sensor Fish record about 2,000 measurements per second as they swim through the turbulent waters and turbines at hydroelectric facilities.
Taking a wild ride
“The Sensor Fish provides information to help engineers design more fish-friendly turbines going forward,” said Daniel Deng, a laboratory fellow at PNNL.
On the journey of less than two minutes in the fast-moving water through a dam, they record acceleration, orientation, pressure and the speed at which the sensor fish rotates.
It allows dam operators to help understand the stresses on real fish, such as juvenile salmon, as they take a potentially wild ride through dams and then make improvements to structures.
PNNL began developing the Sensor Fish in the late 1990s to improve fish survival at the hydroelectric dams along the Pacific Northwest’s Columbia River Basin, including on the Snake River.
“The vast majority of juvenile salmon and steelhead passing through the turbines survive without injury in the Columbia River Basin,” Deng said. “Still we want to understand more about the injuries and mortality that do occur from abrupt pressure changes in dam turbine chambers.”
Fish can be hurt or disoriented by the turbulence of the water and the blades of a turbine can strike them, if that’s the route they take through the dam. But PNNL research with an early version of the Sensor Fish has helped show the pressure changes in the dam turbine chambers that also can harm fish.
A fish traveling through a dam can experience an enormous drop in pressure in an instant and just as quickly return to normal pressure, according to PNNL.
The lab compares it to a human zipping to the top of Mount Everest in the blink of an eye.
The sudden pressure changes can injure or kill fish that depend on a balloon-like organ known as a swim bladder to maintain buoyancy at different depths.
The bladder shrinks as the fish goes deeper and pressures are greater and increases in size as the fish rise, instantly expanding four or eight fold in some species.
Redesigning dam turbines
Data provided by the Sensor Fish can help to redesign dam turbines so they create less severe pressure changes while maintaining or even improving power production, according to PNNL.
The original design of the mechanical fish has been replaced by the second-generation of the Sensor Fish, which is smaller and more accurately captures the experience of a real juvenile salmon swimming through dams.
It is shaped not like a fish, but a small, clear cylinder with two weights. It can be programmed to drop the weights at a specific time, causing the Sensor Fish to pop to the top of the water after it makes its trip through the dam.
Flashing LED lights and radio signals allow them to be collected quickly from boats stationed nearby to be reused over and over again.
In recent years the Sensor Fish has been used by PNNL to collect data in the United States, Australia, France, Germany and Southeast Asia.
Growing interest in the device has led to a license agreement with Advanced Telemetry Systems of Minnesota to manufacture and market the fish and allow hydropower operators and other researchers to collect their own data.
Deng sees demand in the United States as aging dams are retrofitted with more fish-friendly turbines.
Many large U.S. dams were built in the 1970s or earlier and also are facing relicensing, which requires an evaluation of their environmental impact, including how fish fare when swimming through dams.
They can be used to collect data not only in passage through turbines but other routes fish get through dams, including spillways and bypass structures.
They also could be useful for new hydropower facilities being built around the world.
“Many people in Southeast Asia rely on fish both for food and their livelihood,” Deng said after the Sensor Fish were used in a study on creating sustainable hydro in the Mekong River, which passes through Laos and Cambodia. “Hydropower is also a critical resource in the region.”
It’s why he does research — to make an impact on people’s lives, he said. With the Sensor Fish technology moving from the laboratory to commercial availability, the impact should grow.