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Scientists 'listen' to fish populations
Researchers study Gray's Reef
Researchers prepare gear to be taken out to the reef. - photo by Photo by Lauren Hunsberger
Most people who spend time on the water in the coastal region are familiar with the idea of fish finders — electronic devices that send signals into the water to locate objects swimming or floating below.
Laura Kracker, scientist and geographer with NOAA, said her state-of-the-art fish acoustics project uses the same principle, but on a much larger scale.
Aboard the Nancy Foster and working in conjunction with other scientists aboard the research vessel stationed at Gray’s reef for nearly two weeks, Kracker said her passion for both geography and fisheries brought her to the reef to study and map the habitat using sonar technology.
“I have brought out two pieces of sonar equipment so that we can look at fish distribution and abundance in the water column. We’re mapping over the entire sanctuary as well as over select dive sites,” Kracker said.
The equipment, which can send sonar signals more than 200 meters deep, works to help the scientists better understand what type of fish community populates the reef.
“With active acoustics you have a signal going down into the water column and it reflects off whatever’s there. So you can tell the size of the fish and the location of the fish,” she said. “The signals are returned in decibels and that decibel reading is relative to types of fish.”
Kracker then collects her data from the visual representations projected onto a computer screen. She said some of the most interesting findings are schooling patterns.
“We’ve found some really interesting images of spade fish that are schooling up into pyramids of five meters high and we think that’s a strategy against predation. Something’s driving them into schools like that and the divers have seen that kind of thing too,” she said.
All of her research and mapping will go toward the growing amount of research, interest and conservation of the sanctuary.
“We’re learning more about the fish we’re trying to save and there are many questions, fundamental questions, that we don’t know like how long does a fish stay in the sanctuary,” said Greg McFall, research coordinator for Gray’s Reef and co-chief scientist of the cruise.
McFall said, however, once the data is collected Kracker, like many of the other scientists, will have weeks of interpretation ahead of her.
“For an 11-day cruise, Laura (Kracker) will probably have about a month of data analysis to conduct. We’re intensely collecting data right now, but it can take months, even years to analyze it and get the whole picture of what’s going on. But like in all science usually when you answer one question it just leads to more,” McFall said.
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