These Submersible Sensors Measure All the Ways Dams Brutalize Fish

Dams can be rough on migrating fish. Visitor7/Wikipedia

Hydropower dams provide almost half of the nation’s sustainable energy, but they can be death traps for fish, particularly juveniles headed downstream. In hopes of engineering more fish-friendly dams, scientists have created small aquatic sensors that record how fish would get spun, stunned, and barometrically burst in the hydroelectric gauntlet.
Called Sensor Fish, each is a sandwich of two circuit boards stuffed inside a water tight cylinder. They were first developed in the late 1990s by researchers at Pacific Northwest National Laboratory, but the early versions were expensive and could only gather a limited amount of data. A paper in today’s Review of Sensor Instruments describes the latest version, which is better, and more cost-effective, at modeling fish stress than its predecessors.
Say you’re a juvenile salmon, or smolt, headed into a massive dam. Spinning turbine blades nearly chop you in half, but they are hardly the only danger. You can also be squashed against concrete, sheared apart by a sudden rush of high pressure water, or even blown up from the inside as your swim bladder expands from the rapid pressure drop on the far side of the turbine. Even if your fishy little body is intact on the other side, you might be so disoriented that you’re easy pickings for a hungry bird. It’s almost enough to make you wish you’d grown up in a nice, safe fish farm.
Sensor Fish records these bumps and pressure changes using an array of accelerometers, gyroscopes, and pressure sensors. These are sensitive enough to tell the sudden, jarring strike of a turbine blade from the gradual onslaught of a high-speed water jet. Auto-inflating balloons make them easy to find in the churning downstream dam water. In dam trials so far, the Sensor Fish’s pressure sensors have measured pressure drops equal to ascending the world’s tallest mountain in less than a second.
In order to correlate the Sensor Fish data with biological trauma, the researchers also inject smolt with tiny acoustic tags to track how far they make it through the dams. “This shows where the fish are getting injured,” said Daniel Deng, the lead scientist on the project, while the Sensor Fish measures exactly what physical stresses caused the injuries.
Sensor Fish will be an important tool for keeping the US’s dams operating as they get older, and need to be relicensed. They will also be useful in developing new types of dams capable of producing smaller, more localized hydro power in the US, and other, large scale projects overseas.
Deng says he doesn’t believe the data will lead to generalized standards, but rather a way of testing the conditions specific to each river, dam, and fish species passing through.

The first sensor fishes were shaped like real fish, but the researchers realized that they actually behaved more like small fish when shaped like cylinders. Pacific Northwest National Laboratory

Source: http://www.wired.com/2014/11/fish-sensor-hydropower-dam/