 Radio Script 2001
Laser Fish
INTRO: One of the fisheries scientists' hardest and sometimes messy jobs is to count fish. Salmon are counted one by one as they swim up clear, freshwater streams and rivers to spawn. Other fish swim in huge schools that make individual counting impossible. Scientists tally these fish by first catching them in nets—and then measuring their mass, or weight. But Doug Schneider reports in this week's Arctic Science Journeys Radio, fisheries managers may in the future rely on lasers to count fish. STORY: It might seem strange to use an airplane to count fish, but that's just what scientists are doing in Alaska's Prince William Sound. Evelyn Brown is a marine scientist at the University of Alaska Fairbanks. She's been testing a remote-sensing tool called LIDAR to see if it can be used in planes to detect concentrations of fish. BROWN: "This project is a pilot study to see how well these remote-sensing tools work. We've got an imager on board as well, so we're looking at two-dimensional surface images that can do really well at bird and mammal counts, and then seeing the subsurface features that they may be associated with—fish schools, plankton layers. We're here for two main goals, to test the limitations of the equipment in Alaskan waters, what depth penetration we can get to…" LIDAR stands for LIight Detection and Ranging. Think of LIDAR as a kind of radar. While radar works by sending out radio waves that bounce off hidden objects to reveal them, LIDAR works by sending out low-frequency beams of light. Jim Churnside is the chief of Ocean Remote Sensing with the National Oceanic and Atmospheric Administration. He's helped turn what was originally a tool for measuring clouds and landmasses from space, into a tool for detecting fish and other marine life. CHURNSIDE: "It's an analog to the acoustic echosounder. It uses a short laser pulse instead of an acoustic pulse. We have a pulse of laser light about six feet long, and it goes down from the bottom of the aircraft into the water, scatters and bounces off of things, including fish. It reflects back up to the aircraft where we detect it with a telescope, and input the information into a computer." One of the big advantages of using LIDAR to spot fish and other objects from airplanes is that planes can cover a lot more ocean than traditional survey techniques that use ships. While a ship can travel only a few miles per hour, planes can fly over 100 miles an hour.
Evelyn Brown is among a group of scientists experimenting with LIDAR in the sound. Their work is aimed at improving the tools of resource management, and is being done with funding from the North Pacific Marine Research Program at the University of Alaska Fairbanks. Brown says another advantage of LIDAR lies in its ability to "see" deep into the water column. BROWN: "We were pretty surprised at the depth penetration with some of the inside waters, seeing, I think, 35 meters. It has the potential for, if the interest is there, surveying the surface waters and the ecology of the surface waters. Right now, this is where a lot of the interest is. Migratory salmon are in the upper five meters; the plankton are in the upper 50 meters. A lot of the birds and mammals associated are near the surface, so it works really well for that." Widespread use of LIDAR as a fish survey technique is probably still a few years off. Software programs that can quickly distinguish between fish, plankton, marine mammals and seabirds have yet to be developed. Still, Jim Churnside says that given the high costs of traditional ship surveys, fisheries managers probably will hear a lot more about LIDAR in the years to come. CHURNSIDE: "As there's more and more pressure on the fisheries, there's going to be more of a need for better information to do a better job at regulating the fisheries. There's not going to be a lot more money for ship days at sea. This is a way to increase the coverage at a much lower cost." OUTRO: This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program and the University of Alaska Fairbanks. I'm Doug Schneider. Audio version and related Web sites (sidebar at top right) Thanks to the following individuals for help preparing this script: Evelyn Brown, Research Associate James Churnside Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
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