As the summer draws to a close, Seascape Ecologist Bryan Legare, Manager of the Center’s Shark Ecology Research Program, has been busy collecting the 60 acoustic receivers used to track the whereabouts of white sharks near the beaches of Cape Cod.
These acoustic receivers record the acoustic signals from sharks tagged with acoustic transmitters. Bryan uses the signals to triangulate the sharks’ positions and is able to determine their location to as fine as one meter.
“I’m studying how the movement and abundance of white sharks is related to the coastal habitat, in short, how white sharks use the shallow waters of Cape Cod,” explained Bryan.
Deployed at the beginning of the summer from the Center’s research vessel Marindin, the receivers are fixed on the sea floor with submerged buoys, eliminating vertical lines reducing the risk for entanglements or interactions with vessels.
They’re set in a grid along one-mile stretch of beach, at depths ranging from one to ten meters, usually within a quarter mile of shore.
Since 2019, the receivers are installed before July 4th, and removed shortly after Labor Day, to prevent loss due to storms. They’ve been deployed at Head of the Meadow Beach for the past five years, Nauset Beach for four years, and for the past two years at Herring Cove, Marconi and Newcomb Hollow Beaches.
Bryan then maps the seafloor utilizing the Center’s mapping equipment, creating data sets of the bathymetry and habitat where the sharks are being tracked. This allows him to see the pathways sharks use to navigate the nearshore geomorphology to access the nearshore habitat. Bryan notes that he was surprised to learn that white sharks tend to hug the bottom as they transit these areas, that finning at the surface is rare.
“We’re able to create a profile of where sharks are most likely to be, so we can inform beach managers and the public about how they want to use the beach,” he said.
The project is supported by the Commonwealth of Massachusetts, the Town of Truro, the National Park Service, and the Atlantic White Shark Conservancy and private donors.
Photo: Seascape Ecologist Bryan Legare with acoustic receivers aboard the R/V Marindin.
