Swimming with Sharks

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by Leslie G. Baehr   Photography by Big Wave Productions,  Illustration by Jack Cook/WHOI

Great White Shark Tracking
So when Kukulya’s boss, Tom Austin, came to her and said, “Amy, I’ve got just the project for you,” it had to be interesting. The project was peculiar—outrageous, actually. They would be refitting one of their autonomous underwater vehicles, or AUVs, to track and film great white sharks. The Discovery Channel was paying for it. For a program for its annual Shark Week.

Kukulya laughed. Were they serious? “It was clearly going to be a very difficult engineering challenge,” she said.
Kukulya wasn’t alone in her doubts. Greg Skomal, who heads the Massachusetts Shark Research Program, wasn’t convinced, either. Even Nick Stringer of Big Wave Productions, the would-be director of the show, knew he was rooting for a gamble. “To be honest, I was completely skeptical about whether it would work,” he said. “I really didn’t think it would, and I think a lot of people involved in the project really didn’t think it would.”  
Stringer had brought the parties together and pitched the project to Discovery Channel. It would use an AUV called a REMUS 100, a sleek, yellow, five-foot, torpedo-looking vehicle that debuted August 2013 on Discovery Channel as “SharkCam.” The beauty of REMUS (an acronym for Remote Environmental Monitoring UnitS) is its low cost and its versatility. In the crudest sense, the AUV is like a Mr. Potato Head: Its body usually stays the same, but various sensors are attached with each new undertaking—an avalanche beacon for under-ice escapades, for example, or sidescan sonar for shipwreck-hunting. 

Different versions of the REMUS 100 had been used to search for underwater mines; to survey the Atlantic continental shelf break for fish; and to examine how ocean currents mix off Cape Cod, but none had ever been used to track a moving animal. REMUS is equipped with sonar and sensors that allow it to use sound to track its position and navigate between points. It is usually preprogrammed to swim along predetermined routes. To track a moving target, the computer brains in REMUS would have to be constantly recalculating the locations of both itself and its target. “It’s a complicated math problem,” Kukulya said.

The only time REMUS had trailed anything in motion was for a system to recover the AUV from an underway ship—with the AUV chasing down and attaching itself to a line trailing the vessel. At least then, the ship was sending REMUS acoustic signals on its position and was moving in a relatively straight line at a constant speed. It was unlikely great whites would do the same.  

Despite the apparent implausibility, all parties opted in. For Kukulya, part of the larger team at WHOI’s Oceanographic Systems Laboratory (OSL), it was the chance to work on a fun engineering challenge in her own backyard.
For Skomal, the lure was the data. Scientists know astonishingly little about the simplest  aspects of great white behavior, let alone where they migrate, mate, or give birth, or even how long they live. In addition, shark sightings off Cape Cod had increased over the past couple of years, and beach managers were desperate for information.  

For Stringer, it was a chance to satisfy his “frustrated scientist at heart” and to film a very good story. “I got really excited,” he said, “because it’s always been something that’s been talked about in the circle of underwater filmmakers that I know, but no one had really attempted it.”
All parties were skeptical, but on board. So was Discovery. Almost. “They were sufficiently excited,” said Stringer, but “they weren’t going to give us all the money. Not without some sort of trial.”

The concept of Shark Cam actually began long before Discovery and Stringer caught wind of it—in 2008, in a Woods Hole coffee shop, with Cabell Davis, a WHOI biologist, ruminating with OSL engineer Gwyneth Packard. Davis said that he always wanted to see if a REMUS could follow a basking shark, so that he could  find out if the planktivorous fish sought out plankton “clouds,” or areas of high plankton concentration.
With a small grant from WHOI, Packard and a team altered REMUS’s computer algorithms so that the target guiding the vehicle’s trajectory would not be a stationary location, but an ever-changing one—in the form of an instrument called a transponder that emitted acoustic signals that REMUS could “hear.” The shark would be tagged with a transponder.

The team installed a key component into REMUS, a navigation system that could hear sounds coming from any direction. REMUS would send out “pings” of sound (“Marco!”), and the shark’s transponder would reply (“Polo!”), giving computers inside REMUS information to calculate the shark’s distance and bearing. Because sharks move through three-dimensional space, REMUS also needed data on depth, which its navigation system normally didn’t obtain. The OSL team programmed the transponder to send out a second ping: processing the time delay between the first and second pings, REMUS could calculate the shark’s depth.

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