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Scientists Put An Ear To The Ocean Floor


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Scientists Put an Ear to the Ocean Floor

BROOKLIN, Canada, Feb 14 (IPS) - Canada will spend 38 million dollars to install thousands of undersea listening posts along the continental shelves of North America, the Mediterranean, Gulf of Mexico and Australia.

Akin to military hydrophones used to detect the underwater passage of submarines, the receivers of the new Ocean Tracking Network will track movements of fish and marine mammals tagged with tiny acoustic transmitters.

And this too is a security issue -- fish stock security.

"This will have an enormous impact on our ability to manage fisheries," said Eliot Phillipson, president and CEO of the Canada Foundation for Innovation, a Canadian-government-sponsored research funding agency.

The Canadian donation is expected to trigger an additional 135 million dollars in funding from global partners in the Ocean Tracking Network (OTN), Phillipson told IPS.

"Marine scientists have never had continuous streams of data from the ocean floor before," said Ron O'Dor, a researcher at Dalhousie University in Nova Scotia who leads the Ocean Tracking Network.

"Eventually up to one million fish globally will be tracked by the network," O'Dor told IPS from Panama City, Panama. "This will change the way marine science does business."

The system not only records fish movements but also temperature, salinity, depth, and in the near future phytoplankton levels, current speeds and more.

Battery-powered, acoustic receivers about the size of a small gym bag are attached to 200-kg steel railcar wheels to anchor them to the sea floor. Placed at regular intervals, 50 to 200 receivers form a line or "listening curtain" up to 50 kilometres long.

Researchers implant marine animals large and small with low-cost transmitting devices that vary in size from an almond to a double-A battery. As the animals approach the listening curtain, the nearest receiver logs the tag's serial number, date and the time. Movement patterns of individual animals, including direction and speed, can be reconstructed using the time of detection at different receivers and other listening curtains.

More than 7,000 animals along North America's west coast have already been tagged and a number of curtains have been place since 2004 to test the concept. The Pacific Ocean Shelf Tracking network revealed for the first time that young Pacific salmon suffered high rates of mortality along the coast and not just in the rivers where they were born as had been assumed. Such evidence is changing the management of salmon and other species.

Another curtain tracking the movements of endangered white sharks off the California coast discovered they have favourite "fishing holes" where they spend more of their time feeding. Combined with DNA samples, the movement data can show where and how large an area will needed to protect this unique species, said Barbara Block, a marine scientist at Stanford University and head of the Tagging of Pacific Pelagics project.

"Knowledge creates power," Block said in an interview.

Listening curtains in the Atlantic will provide clear direction about the management of the highly-prized Atlantic or Northern bluefin tuna, she said. Individual bluefins have sold for 180,000 dollars in Japanese fish markets and are on the World Conservation Union's "Red List" of threatened species.

The first Atlantic curtain comprised of 200 receivers will go from Halifax, where OTN headquarters is located, out to the edge of Canada's continental shelf. It is expected to be operational within two years, said David Welch, chief scientist of the Pacific Ocean Shelf Tracking Network.

Canada has suffered a massive collapse of fish stocks on its east coast, most notably the Northern Cod, and this new technology will for the first time monitor changes in the ocean and how fish are responding, Welch told IPS.

"It looks like changes in ocean temperatures might be reducing the survivability of young cod," he said. "With the Halifax line in place we'll get constant information on sea bottom temperatures."

Lately local fishers have reported large numbers of cod in certain areas and the data collected will show if these various populations or just the same group moving from one spot to another, he said.

Two other Atlantic curtains are under negotiation, one between Florida and Cuba and another between Mexico's Yucatan Peninsula and Cuba.

"The Gulf of Mexico is a marine biodiversity hotspot and we don't know why, when or how long species stay in the Gulf," Welch noted.

Scientists from all three countries are eager to find funding for the project, with Canadian scientists likely to act as liaison between the Cubans and the United States, he said.

"Fish don't pay attention to the political issues of the day," Welch dryly pointed out.

Another curtain is to be raised at the Straits of Gibraltar to track the movements of fish, including the Atlantic bluefin tuna, in and out of the Mediterranean Sea. The strong currents in the Strait pose a bit of technical challenge and a decision on this project is expected this year.

Yet another is currently being put in place on the Australian coast.

The costs are relatively modest at about 10,000 dollars per kilometre, Welch estimates. Batteries on receivers last four to five years before they need to be replaced. Data from the OTN will be collected and shared amongst all the global partners, offering new insight to what is happening under the sea.

Climate change is also affecting the oceans and the network will be able to monitor some of those changes and how fish are responding, he said, adding that, "Without doubt the OTN will rewrite fisheries management."

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