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Stalking Sharks

Researchers monitor the movement of the Pacific’s largest predators and share the information with the world in real time.

By | August 30, 2012

image: Stalking Sharks Great white sharkWikimedia, Terry Goss

Meet L-Town, a male great white shark that was recently detected off the coast of San Francisco. At 4 meters long (13 feet) long and 800 kilograms (1,765 pounds), L-Town is actually one of the smaller members of Shark Net, a new iPhone/iPad app that allows users to follow the Pacific’s greatest predators as they travel the oceans traversing a network of acoustic receivers.

“I realized we have one of the wildest places on Earth here in our own backyard,” says Stanford University marine sciences professor Barbara Block. “We have all these predators, but nobody can see them.”

“I think it’s a great initiative,” says behavioral ecologist David Jacoby, who is just finishing up his PhD at The Marine Biological Association of the United Kingdom. “All good conservation practice should involve and stimulate the public interest, and this definitely does that.”

The project builds on the success of the Tagging of Pacific Predators (TOPP) project, which published a paper in Nature last year reporting the results of 265,386 tracking days from 2000 to 2009 on 23 shark or other predator species in the North Pacific. Block and her colleagues are continuing to tag animals and set up new receivers, tracking more and more sharks across finer and finer spatial resolutions.

“It’s the scale of this thing and the ambition that makes it exciting,” says Jacoby. There’s a lot of acoustic telemetry going on worldwide, but most focuses on coastal areas. “What Barbara’s proposing to do is cover a wide range of open ocean,” he says. “In many respects, that’s quite unique.”

“What we then create are these networks of underwater receivers, both fixed and mobile, that allow us to track predators in real time,” Block says. L-Town, for example, was spotted last week by the program’s newest addition, the Wave Glider. The 7-foot-long, yellow, self-propelled surfboard is equipped with a sensor submerged 7 meters below the surface and an onboard processor that allows it to steer its way autonomously across the ocean. “By harvesting the wave and solar energy, the gliders are able to travel long distance and monitor vast areas without ever having to refuel,” says Block, who is hoping to launch two more robotic boards in the future. (Watch a video of the Wave Glider launch.)

Screen shot of the Shark Net app
Screen shot of the Shark Net app
Credit: Stanford University

Currently the Shark Net app tracks 15 sharks, complete with photos, bios, and detection histories. Some even have 3-D models that swim across the screen, resembling the actual anatomy of the shark. Sightings for this year are just starting to roll in, and “as we get into October, the app is going to be going nuts,” says Taylor Chapple, a postdoc in Block’s lab.

The TOPP project revealed that the California Current, an ocean current that sweeps south from British Columbia all the way to Baja, California, “is the best lunch spot in town,” says Block, who affectionately refers to the current as the Blue Serengeti. Predators from as far away as New Zealand, Indonesia, and Japan will gather just off the coast of San Francisco Bay on an annual basis to take advantage of the numerous seals and other prey species drawn in by the cold current.

“They come back year after year,” Block says, allowing scientists to track them for, in some cases, more than 25 years. “The sharks that we’re studying have a lot of personality,” she says.

Despite these long-term observational studies, “we still know relatively little about population-wide dynamics,” says Jacoby. For example, are sharks really solitary hunters or do they “have any type of real association?” wonders Chapple, who suspects, based purely on anecdotal data, that sharks do create some kind of social ties.

But even more important than the science, in this case, is the potential to protect these animals. The project is geared towards establishing part of the California Current as a United Nations World Heritage Site, which would offer ample protection for a wide-range of species, says Jacoby, from sharks to commercially important fish like tuna.

To get this kind of protection, the researchers need public support, and that’s exactly what the Shark Net project aims to do. “This is allowing us to bring the stories of these sharks to the public,” Block says. “Only in this kind of fashion can we help people see beneath the sea—this incredible ecosystem remarkably rich and intact and full of life.”

See a slideshow of images from the Shark Net project.

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