New Two-year Study Aims To Understand Fine Movements Of Sharks

By: Tim Wood

Topics: Sharks

 State shark biologist Greg Skomal uses a digital camera on a pole to film and photograph a white shark off Nauset Beach.  KAT SZMIT PHOTO

CHATHAM – A two-year study aimed at gaining a better understanding of the hunting and feeding behaviors of the region's great white sharks will get underway within the next few weeks.
A collaboration between the state division of marine fisheries, the Anderson Cabot Center for Ocean Life at the New England Aquarium and the Atlantic White Shark Conservancy, the new study involves placing tags containing accelerometers on white sharks in order to track fine-scale movements, in particular predatory behavior, said AWSC staff scientist Megan Winton.
Accelerometers are similar to devices found in smartphones that allow axis-based motion sensing, such as games and other functions that involve moving or tipping the phone. The devices, known as accelerometer data logging tags, will record the speed and direction a tagged shark is traveling as well as other data.
“Sharks just swimming along have a much different acceleration signal than one actively hunting or eating a seal,” Winton said. Coordinated with other data, this will allow researchers to determine if sharks are “hunting during dawn or dusk, do they hunt during all times of day, or mostly at high or low tide,” she said. A few of the accelerometer tags will also be include video cameras, she added, which will help validate the data.
This is crucial information for public safety as it can inform decisions people make about going into the water. Given the two shark attacks last year—one of them fatal—“there certainly is an increased sense of urgency,” Winton said. Public safety has been the motivating factor behind all of the research on the area's great white sharks conducted by Dr. Greg Skomal, the state's top shark scientist, as well as others, she said.
Added AWSC CEO Cynthia Wigren, “From a public safety perspective, it is critical to get a better idea of hunting and feeding behavior. If sharks are feeding at certain times of the day or stages of the tide, for example, we can use that information to identify periods when the risk of interactions between sharks and recreational water users may be highest.”
The accelerometer deployment is just one of the great white shark studies that scientists will be conducting this summer. Along with tagging great white sharks along the Outer Cape with the accelerometer tags, Skomal and his DMF and AWSC colleagues will be looking for sharks in Cape Cod Bay and tagging them with acoustic tags, which register on an array of receiver buoys deployed throughout the region. Winton said there are now about 70 receiver buoys around the Cape and South Shore, many of them sponsored by businesses and towns. She was helping put out 14 on Monday afternoon and planned another trip later in the week to put out more. Local harbormasters have been a big help in getting the buoys on station.
“We wouldn't be able to get these out by ourselves,” she said. Researchers will be trying to determine if different sharks frequent Cape Cod Bay, where sightings have increased in recent years, and whether their movements are different from the sharks seen along the Outer Cape.
Weekly trips on the water, once again with Captain John King on his Chatham-based vessel Aleutian Dreams, will begin in the next few weeks and continue until late October, Winton said. The accelerometer tags, which she said have been used by shark researchers in other areas, are clamped to the animal's dorsal fin and generally remain in place for one to two weeks. When the tag pops up, it sends an alert with location information. Researchers then retrieve the tag and download the data. Because of the sheer among of high-resolution data the tags collect, it has to be downloaded manually; it would take too much power to transmit the information via satellite, Winton said.
That's both a blessing and a curse, she said. In order to get the data, researchers must retrieve the tag. Since they are on the water frequently, they don't anticipate any problems. The tags can then be reused, meaning the 10 tags they plan to purchase can collect a significant amount of information from a number of different sharks over the two summers they plan to conduct the study.
“It will be a function of how long they stay on the sharks,” Winton said.
A five-year population study by Skomal, supported by the AWSC, was completed last summer and the massive amount of data collected is still being processed, said Winton, who is basing her doctoral study on the information. The data includes still photos, video and information from the tags placed on some 120 sharks that must all be coordinated and sorted. Researchers hope the study will provide an accurate picture of the number of great white sharks in Cape Cod waters.
Winton said the public can follow the research on the AWSC and DMF websites and social media accounts. The AWSC has also set up an email address for inquires,
“If you have questions, ask,” she said.