This Fish Drone Shows What Really Happens to Salmon When They Pass Through a Hydroelectric Dam
Think about what it must be like to be a salmon.
You can complain about your commute to work, littered with potholes, missed public transportation, and spilled coffee, but consider the first trip a juvenile salmon has to make.
From far upstream, the fingerlings make the trek to the open ocean, dodging predatory birds, fish, and sea lions along the way. There’s also a good chance they’re dodging turbine blades and swirling around in man-made currents from hydroelectric dams.
It all sounds rough. But what does it feel like? That’s where Sensor Fish comes in.
A technical drawing of the latest version of the Sensor Fish, illustrating the various directions in which the device’s motions are recorded. (Infographic: Flickr)
Developed by Pacific Northwest National Laboratory researchers, the synthetic, tubular “fish drone” has been programmed to tell scientists what salmon experience when passing through dams.
At Washington’s Ice Harbor Dam, on the Snake River, the fake fish was sent through the turbine chambers and swirling waters real salmon must navigate to get from upriver to downstream of the dam.
In nature, most fish make it through the chambers unscathed—a survival rate of 90 percent is typical at U.S. dams. The 10 percent that don’t make it have long been thought to be victims of turbine blades, but PNNL’s Sensor Fish has discovered another fish killer: pressure change.
As the fish pass through the various chambers, salmon are experiencing extreme pressure changes, similar to what we’d feel if we took an elevator from sea level to the top of Mount Everest in less than a second.
Daniel Deng, a chief scientist at PNNL, and fellow researchers discovered this while studying their first Sensor Fish iteration back in 2004.
“The earlier Sensor Fish design helped us understand how intense pressure changes can harm fish,” Deng wrote in an email. But the first-generation model was only designed to test dams equipped with a certain type of turbine used along Washington’s Columbia River.
The new model takes more accurate readings of turbine and chamber pressure effects found in a variety of hydroelectric dams around the world.
“It’s now able to study the fish-friendliness of dams throughout the U.S. and abroad, not just in the Pacific Northwest,” said PNNL spokeswoman Frances White.
Half of the U.S.’ renewable energy came from hydropower in 2013, and most of the country’s power-generating dams were built in the 1970s or earlier. Now many are up for relicensing—a process that requires dam operators to show they’re taking the necessary steps to reduce environmental impacts.
White said the idea is to deploy the Sensor Fish to test effects of new turbine designs at retrofitted dams.
“Each individual dam is unique and can have many different factors that contribute to fish survival and injuries,” White said. “One can’t make a blanket statement that any one turbine type or any one dam type is more dangerous to fish than another. Experts need to carefully study the unique characteristics of each individual dam to fully understand which specific areas of that dam could be more dangerous for fish.”
After successful testing runs in Washington, Deng has deemed the new Sensor Fish ready for testing abroad. On the schedule so far are three small hydroelectric projects in the U.S., multiple dams in Australia, and a dam on the Mekong River in Southeast Asia.
“As we’re increasingly turning to renewable energy, these measurements can help further reduce the environmental impact of hydropower,” Deng said.