Scientists Use Ocean Listening Curtains to Track Tagged Animals

HALIFAX, Nova Scotia, Canada, July 3, 2006 (ENS) - Ocean scientists from around the world have plans to surgically insert electronic tags into thousands of ocean animals and follow them with extensive arrays of acoustic receivers on the sea floor. Deployed in all major oceans, the receivers will scan the tags the way bar codes on products are scanned at a store check-out.

Winding up a four day conference at at Dalhousie University on Friday, the scientists of the Canadian-led Ocean Tracking Network said they plan an interconnected network of receivers that spans 14 ocean regions - in the Arctic and Southern Oceans, the Indian Ocean, the Atlantic, the Mediterranean, and the Pacific.

"Every fish, every pelagic animal is a submarine and we have much to learn by electronically harvesting information about their movements," says professor of biology Dr. Ron O'Dor, who heads the Dalhousie based Ocean Tracking Network, which hosted the meeting. "Today we know less about our marine life - how these animals live, where they go - than we know about the back side of the moon."


Tags implanted in the animals' abdomens send out unique signals, which are picked up by receivers placed on the ocean floor. (Photo courtesy POST)
D'Or also serves as a senior scientist with the 10 year long Census of Marine Life. Through 2010, scientists worldwide will work to quantify what is known, unknown, and what may never be known about the world's oceans. More than 1,000 scientists from 70 countries are involved in the Census of Marine Life, of which the Ocean Tracking Network is a part.

"Revolutionary new technologies open the path not just to smarter fisheries management, to better sea life conservation measures, and to the potential of abundant and sustainable stocks of commercial fish, they will also provide scientists with a massive increase in observations of rapidly shifting marine conditions in this era of climate change," says D'Or.

The global research network aims to address problems such as climate change, ocean modeling and marine living resource management using listening curtain technology.

The scientists are implanting the tagging devices, ranging in size from an almond to a AA battery, in fish and marine mammals. As the animals move, the tags collect and report information on their location and on the water temperatures, salinity and light conditions they encounter at various depths and locations.

Depending on the type of tag used, the data is captured when an animal surfaces, sending the archived data to a satellite, or when it passes one of many acoustic receivers arrayed on the ocean floor along the coastal shelf. Or the data can be read when an animal is caught again.

A pilot array has been demonstrated by the Pacific Ocean Shelf Tracking (POST) Project based in Vancouver, British Columbia, working since 2004 as part of the Census of Marine Life.


The acoustic receivers used in POST's 2004/2005 demonstration phase are lined up ready to be deployed in the northern Strait of Georgia, British Columbia. Each unit is equipped with a flotation device, acoustic modem and acoustic receiver (Photo courtesy POST)
Currently, the POST array stretches more than 1,750 kilometers (1,087 miles), from Oregon through British Columbia to north of the Alaskan panhandle.

The project has shown the Pacific migration routes of young wild salmon from U.S. and Canadian rivers. Knowing their usual travels along marine highways helps authorities determine when fisheries should be open or closed to conserve endangered fish populations.

Gerry Kristianson, who chairs the POST Management Board, says the group's vision is the creation of "a permanent ocean telemetry system along the Pacific coast of North America" to serve as an open science platform for users from governments, universities and other agencies in Canada and the United States.

Other scientists from around the world attending the conference have placed tags on a wide variety of fish species, including sturgeon, halibut, sharks and tunas.

Researchers with the Tagging of Pacific Pelagics (TOPP) Project based in California have been tracking large open ocean animals with tags that report in via satellite whenever the animals surface.

Jointly run by Stanford's Hopkins Marine Lab, the University of California, Santa Cruz's Long Marine Laboratory, NOAA's Pacific Fisheries Ecosystems Lab, and the Monterey Bay Aquarium, TOPP also includes team members from several countries.


Members of the Yurok Tribal Fisheries Program in Klamath River in California release tagged a green sturgeon that was later detected by POST listening arrays. (Photo courtesy POST)
TOPP scientists have tracked about 2,000 individual Pacific Ocean animals spanning 21 top predator species, including whales, tuna, elephant seals, seabirds, sea turtles and sharks.

In the newly created Northwestern Hawaiian Islands Marine National Monument, animals tagged in the TOPP project are sending back data that can be read online. Visit: to see the locations of tagged mako, salmon and blue sharks, elephant seals and California sea lions, leatherback and loggerhead sea turtles, and black-footed albatross.

"Tiny microprocessors and sophisticated remote sensing systems now make it possible for scientists to explore the vast reaches of the open ocean from the perspective of the marine animals, whose extraordinary travels make them highly effective oceanographers," says the project's principal investigator, Professor Barbara Block of Stanford University.

Scientists with the POST project explain that they take care to ensure that the animals do not suffer during the surgical procedure that implants the tags.

Surgery takes place at on-site "field hospitals," they explain. Each is a portable surgical unit, constructed to be compact and transportable without compromising surgery quality.

The surgical units include surgical tools, a surgery table, air supply, temperature and oxygen meters, sedative and anaesthetic baths, holding and recovery tanks, and reference manuals for surgical procedures.


A scientist implants a tag into an anaesthetized steelhead trout smolt. (Photo courtesy POST)
Fish are first calmed with a pre-operative sedative to reduce handling stress, and then fully anaesthetized with an approved anaesthetic. Aerated anaesthetic water is continually pumped over the fish's gills throughout surgery, and a paper towel moistened with a synthetic mucus solution protects its eyes from UV light. The surgery cradle, made of a soft, skin-like neoprene and coated with the synthetic mucus solution to preserve the mucous barrier on the fish's skin, supports the fish during surgery.

Following surgery, fish are kept in a darkened holding tank and released at dusk to reduce the risk of predation. Hatchery-reared smolts can be tagged any time prior to release.

Staff are trained to ensure high survival in these very small smolts, and the highest standards of animal care are emphasized to ensure ethical treatment of the animals tagged, according to a POST statement.

The scientific results from the studies on these animals could be compromised if the highest standards of animal care are not maintained in order to minimize stress or suffering. As tags are expensive, high survival is important for economic reasons.

The Ocean Tracking Network says funding sought from Canada of roughly US$32 million to supply the Canadian array technology would potentially leverage total spending by all partners estimated at US$150 million for ship time, tagging, data harvesting and interpretation.