Getting to Know the Neighbors: Sand Tiger Shark Research in Boston Harbor

Thanks to the New England Aquarium’s location on Boston Harbor, we get to share a backyard with many of the marine animals we study and protect. Some of the more unexpected summer residents in the neighborhood, from about July to September, are sand tiger sharks. These sharks may look intimidating, with rows of narrow, sharp teeth visible as they swim, but they are docile and not aggressive toward humans (as long as humans aren’t aggressive toward them).

The International Union for Conservation of Nature lists sand tiger sharks as critically endangered on a global scale, with the US East Coast population declining 70-90% by the early 1990s due to overfishing. But since becoming prohibited on federal and state levels in 1997 and 2009—which means all caught sand tiger sharks must be released—they’ve started to rebound and regain their status as one of the more abundant sharks in Massachusetts coastal waters. These sharks are also now traveling to regions north of Cape Cod, where they were rarely seen even at the population’s peak, including Boston Harbor. 

In 2016, scientists with the Aquarium’s Anderson Cabot Center for Ocean Life began tagging sand tiger sharks in Boston Harbor to learn about their usage of the area and bolster conservation efforts. Because Boston Harbor—including Dorchester Bay, Hingham Bay, Broad Sound, Nahant Bay, and Quincy Bay—is a metropolitan area with lots of human activity, it’s crucial to understand where and when sand tigers are found in the harbor and what protections they might need.

Why are sand tiger sharks in Boston Harbor?

Individual sand tiger sharks can grow up to about 10 feet long, but the residents of Boston Harbor are considerably smaller, only about three or five feet long. Why? Because Boston Harbor appears to be acting as a nursery for juveniles. Our scientists see sand tiger sharks from the year they’re born and up to three years old. Sand tiger sharks are born in the late winter and early spring along the southern US East Coast, off of the Carolinas and Florida, where their small size puts them in danger of becoming lunch for bigger sharks. Unlike most species, in which adults are the ones to migrate, sand tiger shark pups and juveniles travel hundreds of miles northward for the summer months to escape these predators and forage for food over their first few years of life.

While it was once rare to see a sand tiger shark north of Cape Cod, many now find sanctuary in Boston Harbor and beyond. Scientists theorize that warming ocean temperatures and/or the abundance of Atlantic menhaden—a key component of sand tiger sharks’ diet—may be contributing to this change as the population recovers.

“The habitat here is favorable for sand tiger sharks’ growth and development,” said Ryan Knotek, PhD, research scientist with the Aquarium’s Anderson Cabot Center for Ocean Life. “At this critical stage of their life, these sharks are choosing Boston Harbor because it’s providing protection from predators and abundant food sources.”

The conditions are favorable enough that our scientists have observed some of the same juvenile sharks returning to the area for consecutive summers! 

How and why do we study them?

In 2023, the sand tiger shark project was relaunched after preliminary tagging from 2016 to 2019, and our scientists tagged a record number in Boston Harbor. 

We use passive acoustic telemetry to monitor the movement of sand tigers, which works a lot like an E-ZPass system for sharks. Acoustic tags on sharks transmit ultrasonic signals that are detected by any nearby underwater receivers at fixed locations in the harbor. Using data collected from the receivers, scientists connect individual sharks to specific places and times. With enough data, they can find patterns in the sharks’ movements.

In recent years, with the help of an extensive receiver array throughout Boston Harbor maintained by the Massachusetts Division of Marine Fisheries, we’ve been able to more closely monitor shark activity. This includes receivers in key locations such as Wollaston Bay (a preferred area for these sharks), harbor openings (to track sharks entering and exiting the harbor), and other unexplored areas they may also frequent.

“The goal right now of this study is to really pinpoint where these sharks are hanging out and when they’re there,” Ryan said. “Boston Harbor is such a busy, metropolitan area with potential environmental impacts that we need to keep an eye on this species and the areas they’re using.” 

When Anderson Cabot Center for Ocean Life Senior Scientist Jeff Kneebone, PhD, was earning his doctorate, he conducted similar research in Plymouth, Kingston, Duxbury (PKD) Bay, a tidal estuary on Massachusetts’ South Shore. His identification of the bay as a significant sand tiger shark nursery earned it status as a Habitat Area of Particular Concern from the National Oceanic and Atmospheric Administration, highlighting its importance for conservation for the animals there. 

What did we learn in 2024?

During the most recent research season, from August to October 2024, the team saw more individual sharks in Boston Harbor and tagged three of them. While the sharks had some favorite hangouts, including the Wollaston Bay location that’s been popular in previous years and a new Hingham Harbor spot, sand tigers moved widely throughout Boston Harbor. At least one swam by Castle Island, right near the Aquarium! 

Since this research took place close to the Aquarium, staff from the Animal Care, Rescue, and other departments were invited to “tag along” on fieldwork in the harbor. They assisted Ryan and his team with shark tagging and sampling, sharing techniques and tips with each other along the way.

“I really enjoy working with people from other departments at the Aquarium and appreciate their help with the research,” Ryan noted. “And as an integrated conservation organization, spending time on the water is a great way to keep us connected!” 

Next year, the team plans to continue sand tiger shark research with these cross-departmental trips and may also extend the timing of the research season and geographic areas of focus. For instance, shifting focus to tag more sharks from the Hingham Harbor group in 2025. 

Another change scientists are considering for next year is giving tagged sharks names instead of numbers. The battery in acoustic telemetry tags can last for many years, and a data-sharing network allows us to watch tagged sharks as they swim south in the fall and back to our region each spring, until they outgrow the nursery in our backyard. 

“We get a chance to see these little sharks grow up,” Ryan said.