Ryan Knotek stopped his boat and dropped anchor about a third of a mile off of Wollaston Beach. If he had the time, he could drink in the quintessentially Boston view: The skyline to the north, an outcropping of rocks where the chief of the Massachusett tribe used to hold meetings in front of him, one of Quincy’s Dunkin’ Donuts closer to shore.
But Knotek, a New England Aquarium researcher, was too busy to admire the sights. He was there to catch some sharks.
Once upon a time Boston Harbor was one of the dirtiest ports in America. But decades of cleanup have turned it into an ecological haven for species like the sand tiger shark. By catching and tagging the generally placid fish, scientists hope to understand why they’re here, where they go, and what it means for them with a rapidly warming North Atlantic.
Knotek and his colleague, Emily Jones, are both with the aquarium’s Anderson Cabot Center for Ocean Life. They spend a lot of time in this inlet because young sand tiger sharks spend their summers there too.
“It’s nice and sheltered, there aren’t big sharks,” Jones said. “So it’s, like, a safe place where they know they’re gonna find prey.”
Their team has tagged and tracked juvenile sand tiger sharks in Boston Harbor for almost a decade. Their research shows the same sharks come back year after year as the weather warms.
“You have this harbor that was at one point considered one of the dirtiest harbors in the US, and now these sharks are choosing to use this harbor for their summertime nursery ground,” Knotek said.
It’s a remarkable comeback story for a species that was once chronically overfished, with their population dropping by more than 70% along the East Coast, according to Knotek. The International Union for Conservation of Nature lists sand tiger sharks as critically endangered on a global scale.
Federal and state regulations banned the fishing of these animals, starting in the late ‘90s.
“For the better part of two decades, they’ve had these protections, and we’re starting to see recovery in their numbers,” Knotek said.
Each trip, the team baits their rods with frozen pogies and casts them out in hopes of catching a shark. Pogies are a favorite food for sand tiger sharks.
This bait is usually enough to land one, but if not, the team puts on music for luck. Knotek says their current list of favorites are Jimmy Buffet, the K-Pop Demon Hunters soundtrack and anything by Taylor Swift.
“They’re absolutely Swifties, fun fact,” Knotek said.
Once a shark is hooked, they bring it on deck, put it in a cooler and flip it on his back. That puts the shark into a sort of trance, called tonic immobility. The scientists then make a small incision in its belly and insert an acoustic transmitter, which allows the team to track the sharks they tag.
“So the same idea as your E-ZPass transponder in your car, and as soon as they swim by one of these receivers, the receiver detects that ping, it records which animal was there and what time it was,” he said.
Since 2023, the project has tagged about two dozen sharks, including four new juveniles this year. The New England Aquarium monitors about a dozen receivers in the harbor that track the sharks. All that data helps scientists figure out the best ways to support the sharks.
On a recent trip, Knotek analyzed data from two receivers in the Bay. They showed some familiar faces were still hanging around.
“So that shark that we also tagged last year on Sept. 5 has also been right over here within, like, the last half hour,” Knotek said. “So the shark’s moving around a little bit, but they are here.”
Some researchers up and down the East Coast use the same tech, which allows them to share data about the sharks’ habits. It also lets them share information about threats, be it from fishing, habitat loss or climate change. The International Union for Conservation of Nature estimates a third of shark species globally are at risk for extinction.
With ocean water warming due to climate change, we may see more of them in the coming decades.. The sharks can’t regulate their own body temperature, so they depend on just-right water to warm and cool themselves. That means moving to different regions, depending on the season. Because temperatures in the North Atlantic are some of the highest ever recorded, sharks are seemingly traveling farther north than they had before.
Sharks, even juveniles like these sand tigers, are at the top of their food chain, according to Jones. Their health is an important marker for the rest of the ocean.
“It’s like the canary in the coal mine,” Jones said. “If the sharks aren’t doing well, something underneath them is broken. So they can be a really good indicator species, which makes them powerful to study.”
This article was originally published on WBUR.org.
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