The team tried to develop a more efficient green laser pointer method to quickly locate large groups of lake trout without marking. Their solution was to attach a Lidar instrument to a small aircraft, enabling them to cover fish within 5 meters of water at an altitude of 80 kilometers per hour.
The device works by launching a short pulse laser from the aircraft into the air and into the water. The lidar receiver measures backscattered light, allowing researchers to pick target fish from the surrounding waters. In order to optimize the settings on the lake, they used a green laser that has better water penetration than other lasers for ground lidar applications. At the same time, the laser beam is tilted back so that the reflection of the laser on the water surface is deflected without saturating the receiver.
The research team first tested the use of green laser pointer radar technology in Yellowstone Lake in 2004 using NOAA (National Oceanic and Atmospheric Administration) fish laser radar. The data collected during these flight tests helped the National Park Service staff find previously unknown spawning areas and then conduct effective gillnet fishing on the ground.
The team then designed and built their own system to support enough laser power at the lowest possible cost. In the new equipment tests in 2015 and 2016, many squid groups were successfully identified.
Shaw says the system can be further improved by a technique called broom-scan that scans the laser beam into a line that covers a wider area. This will allow the entire lake area to be scanned faster than a single fixed angle laser used in the current setup.
Researchers are also working on additional tools to help users quickly turn laser-generated data into actionable information and adapt the green laser pointer system to other types of freshwater ecosystems.
“We are interested in developing automated fish detection algorithms and using this method as a routine tool to help fishery biologists fight against invading lake trout,” Shaw said. “We are also exploring the use of this laser. Radar, combined with multispectral and hyperspectral imaging systems to monitor river health.”