The new instruments provide fast, low-cost tools to deal with the ecological degradation of Yellowstone National Park in the United States.
According to the report of Memes, the National Park Service has been trapped in a struggle with lake trout (also known as Lake Red Dot) for decades. This is an invasive fish with very strong appetite. It has destroyed and subverted the previously prosperous ecosystem of Yellowstone Lake. According to the latest research, using an instrument mounted on an airplane, it is possible to provide a faster way to locate and capture non-native fish within a few weeks of spawning in shallow water.
"Scanning" Yellowstone Lake from the plane, searching for invading lake trout
The instrument uses a laser-based laser radar (LiDAR) to help lake managers catch invasive fish over a wide area at a lower cost, making more efficient use of the annual cost of lake squid control. $2 million in funding.
In a recent study published in the Optical Association (OSA) magazine Applied Optics, the researchers reported the results of a series of flight tests that successfully located the location of the lake trout and identified previously unknown spawning areas. They showed that the technology could find two or more lake trouts that snorkeled 15 meters below the surface of the water.
“The key issue to be addressed in our research is to find a way to determine the spawning position of the invading lake trout so that fish biologists can apply various methods to reduce the proliferation of fish stocks,†Montana State University Joseph A. Shaw said, “There are several other ways to track these fish, such as sonic sensing, but the aircraft can cover a larger area of ​​lake water in a shorter period of time than the ship.â€
New method of searching in the lake
Lidar (LiDAR) has been used to track fish in marine ecosystems, but this is the first time it has been used to study fish in lakes, where the water in the lake is more turbid.
In addition, while other lidar applications require expensive, complex equipment, Montana State University engineers have developed less than $100,000 in new instruments and are optimized to run on single-engine aircraft at a cost of 500 per day. The US dollar makes it a practical solution for ecologists and local fisheries and water managers.
“Our relatively low-cost, small-sized lidar system can be used for other types of ecological research, such as plankton mapping and plumes from underwater vents,†Shaw said. “It’s hard to get far from the ground. The lake can now be easily mapped and researched in one day."
Manage threatened ecosystems
Located in the heart of Yellowstone Park, Yellowstone Lake has always been popular with fishermen, especially grizzly bears, vultures, otters and other wildlife. Since the introduction of non-native lake trout in the 1990s, the intricate ecological balance of the region has been greatly disrupted.
Lake trout prey on native cut-throat trout in the lake, and cut-throat trout has historically been an important source of food for many top carnivores. With the increase in the population of lake trout, the number of cut-throat catfish has decreased dramatically, dropping by 90% between 2000 and 2005. This greatly reduces the food supply for bears, birds and other animals. These animals are not able to prey on invading lake trout because the lake trout lives in deep water most of the time, unlike cut throat fish.
In order to extinguish the number of lake trout and give the cut throat squid a chance to recover, among other methods, lake managers also use gill nets to fish during the spawning season of the lake trout. Although this method is very effective, it is more important to know when the lake trout is laying eggs.
In order to locate the fish, biologists are currently implanting sonic emitters in individual fish and then tracking them in the lake and on the ship's receiver, which is a time consuming and labor intensive process and does not completely cover the invasion. The location of the fish.
Going into the air, covering a wider area
The research team tried to develop a more efficient way to quickly locate large groups of lake trout without marking. Their solution was to attach a lidar instrument to a small aircraft so that they could 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. To optimize the setup on the lake, they used a green laser that has better water penetration than other ground lidar lasers. 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.
System test
The research team first tested the use of lidar 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 a 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 Lidar-generated data into actionable information and adapt the 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 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."
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