Editor's Notes
Visionaries: An eye toward the future

New version of ESIP monitoring map available

Gulf Voices
A day on Great Bay: In search of the osprey

Science Insights
Dam removal

Profile: Dale Joachim of MIT’s Project Owl

Visionaries: Protecting the future of the Gulf of Maine

Book Review
Soaring with Fidel

Inside the Gulf of Maine Closure Area

Shipping lanes shifted to protect whales

Visionaries in the Gulf of Maine

Ocean Tracking Network to shed light on undersea life

Ambassador for his species: If a whale could speak

On the trail of invasive species

In the News
- Outside the Gulf
- Sappi Paper to remove dam on Presumpscot River
- MIT builds robotic fin for submersible vehicles
- New Brunswick to restore Petitcodiac River
- New Brunswick, Nova Scotia to jointly study Fundy tides

Ocean Tracking Network to shed light on undersea life
By Stephen Leahy
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Imagine a spotlight on the ocean floor just off of Halifax, Nova Scotia, powerful enough to create a tube of light 400 metres or 1,312 feet in diameter and 20 kilometres or 12 miles out to the edge of the Scotian shelf. And imagine what this tube of light might reveal operating continuously.

While no such spotlight exists yet, there soon will be something akin to it. A series of up to 212 acoustic receivers, one every 732 metres (800 yards) or so on the ocean floor, soon will create an “acoustic curtain” 180 kilometres (112 miles) offshore of Halifax to the edge of the continental shelf that will detect fish, seals, whales and other marine animals tagged with tiny ultrasonic transmitters.

“We’ll be able to detect exactly when Atlantic salmon from the Gulf of Maine pass by on their way to Newfoundland and Labrador,” said Ron O’Dor, a researcher at Dalhousie University in Halifax. Sensors also will detect temperature, salinity, pressure and current speeds, offering new insight into when animals move and under what conditions. This could fundamentally alter the management of fisheries. “Marine scientists have never had continuous streams of data from the ocean floor before,” he said.

O’Dor is the prime mover of the ambitious C$200 million (US$173 million) Canadian-led Ocean Tracking Network (OTN). Canadian government research agencies, including the Canada Foundation for Innovation, committed C$45 million (US$39 million) to the project in part because much of the technology is Canadian.The grand vision is to establish as many as 60 acoustic curtains around the world with one million marine animals sending data in real time in 14 regions off of all seven continents.

Listening curtains
In the OTN scenario, transmitter tags as small as an almond or up to an AA-sized battery are surgically implanted in animals. Battery-powered acoustic receivers about the size of a large soda bottle are attached to 200-kilogram (441-pound) steel railcar wheels or concrete blocks to anchor them to the sea floor. Placed at regular intervals about 50 to 200 receivers will form a line or listening curtain up to 50 kilometres (31 miles) long in various parts of the world. As a tagged animal approaches the listening curtain, the nearest receiver logs the tag’s unique serial number, the date and 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.

Since most species stay along the highly productive continental shelves, the receivers offshore from Halifax, called the Halifax Line, will detect virtually any tagged animal heading north from the Gulf of Maine and determine if it returns. Continental shelves average about 80 kilometres (50 miles) wide and the edge of the shelves occur at an average depth of about 200 metres (660 feet) before falling off steeply into the deep sea. Salmon and many other marine animals travel extensively along the shelves. “With similar technology in use in the Pacific, we found that the curtains are about 95 percent efficient. Only one in 20 tagged fish slips by undetected,”said O’Dor.

To date, information on fish has been received from a research vessel bouncing sonar acoustic signals off of a fish’s air-filled swim bladder. But it has been difficult to get detailed information about a fish’s movement, let alone the water conditions at its location.

A pilot project of receivers and fish with transmitters, called the Pacific Ocean Shelf Tracking project and stretching 1,750 kilometres (1,087 miles) from Oregon through British Columbia and north to the Alaskan panhandle, has been demonstrated successfully. The project, part of the international Census of Marine Life, discovered for the first time that young Pacific salmon suffered high mortality rates along coastlines and not just in their natal rivers. On the East Coast of North America, Atlantic salmon populations remain in trouble. There have been high levels of mortality during migration in recent years. The cause remains a scientific mystery.

Unraveling migration mysteries
About 350 salmon smolts on the East Coast of North America along with striped bass, American eels and shad already have been tagged with transmitters as part of other tracking projects, said John Kocik, research fishery biologist at the National Oceanic & Atmospheric Administration’s Northeast Fisheries Science Center in Orono, Maine. “The OTN will greatly enhance our ability to know where our tagged fish are going.”

Peter Smith, an oceanographer at the Bedford Institute of Oceanography in Halifax who is in charge of installing the Halifax Line, said he is waiting for new equipment. In the Pacific the receivers can only upload their data to boats passing overhead, thus requiring regular visits. The Atlantic portion of the OTN will incorporate an improved idea: “daisy chaining.” That means receivers in the Halifax Line placed roughly 800 metres (2,625 feet) to 1,000 metres (3,282 feet) apart will transmit their data acoustically from the furthest out to the next one closer to shore and so on until the data are relayed by a cable system to Halifax, and with only a few seconds’ delay.

“We’ll also supplement the receivers with other sensors to get more information about currents and temperatures,” said Smith. “It will be a window on what’s going on down there.”

The data from the Halifax Line as well as all other electronic curtains will be uploaded via the Internet to the OTN central database in Halifax, enabling scientists from around the world to understand animal movements. This data will be invaluable to detect behaviour changes as the oceans warm due to climate change. It also may be possible to follow the spread of invasive species.

Dalhousie also plans in 2008 to place several antennas onto Gulf of Maine Ocean Observing System (GoMOOS) buoys in the Gulf of Maine. Those antennas will be able to upload data from the receivers on the ocean floor and relay it to satellites that in turn will send it to computers in the GoMOOS network on shore, said Mike Stokesbury, a biologist at Dalhousie working on the OTN project.

“It’s all a little overwhelming,” said Stokesbury.

Stephen Leahy is an environmental journalist in Toronto, Canada.

Can you hear me now?

Water transmits sound five times faster than air and is an ideal environment for acoustic communication as used by whales, dolphins and other marine animals.

The Ocean Tracking Network’s acoustic tags implanted in animals transmit a series of ultrasonic sound “pings” called a pulse train that contains a code. An individual marine animal with its own code can then be identified when it comes close enough to a receiver, which is essentially an underwater microphone.

All tags are tested before use to make sure their ultrasonic pinging doesn’t attract predators or affect other species.

The tags are not removed from the marine animals, and depending on the size, tags operate for 18 months to several years before batteries die.

For more information see the Ocean Tracking Network and the Pacific Ocean Shelf Tracking project.

For additional info about the Gulf of Maine including maps, photos, current research, the NGO database, and to download other educational
publications please visit The Gulf of Maine Council on the Marine Environment.
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