SHARKS are trekking thousands of miles to an unusual vacation spot, and their behavior is puzzling scientists.
The sand tiger shark is a large, bulky species that can grow up to 12 feet long and weigh up to 640 pounds.
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It is best known as the only shark to gulp mouthfuls of air before returning to its watery abode, storing the air in its stomach as it waits for prey to cross its path.
Sand tiger sharks are born in the waters off Florida and North Carolina.
However, a population of juveniles has been making a pit stop in an unexpected destination up north – the Boston Harbor.
Researchers at the New England Aquarium have kept busy, tagging, releasing, and tracking the sharks, which are suspected to be using the Harbor as a nursery ground.
While there is no single definition for a nursery, a 2007 paper defined it as a region where juveniles occur at higher densities, successfully avoid predators, and grow faster than in other habitats.
Sand tiger sharks head north immediately after birth to avoid predators, namely larger sharks.
The waters around Massachusetts also provide a buffet of their preferred food, the Atlantic menhaden.
Still, most Bostonians wouldn’t expect to see sharks in their city, especially not in the Harbor.
Once referred to as the dirtiest water in America, the Boston Harbor was brewing with heavy metals, raw sewage, and nitrogen-rich wastewater.
Cleanup efforts began in earnest in 1991, when the Massachusetts Water Resources Authority embarked on a multi-year project to reduce pollution.
Attempts have lasted to the present day, and scientists take the return of sand tiger sharks as a sign that conditions are improving.
The species was the most common shark in coastal southern New England in the early 1900s.
However, overfishing along the East Coast wiped out 70% to 90% of the population between the late 1970s and early 1990s.
The Massachusetts state government began demanding fishermen release captured sand tiger sharks, but this wasn’t a quick fix.
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The species faces an uncertain future and is currently listed as Critically Endangered on the International Union for Conservation of Nature (IUCN) Red List.
Despite being protected in countries like the United States and Australia, the species is at risk of disappearing forever if numbers continue to decline.
Luckily, researchers are working to bring them back from the brink.
At the New England Aquarium, this means constant monitoring. Researchers capture the sharks using a rod and reel, like traditional fishing, before tagging them.
Each shark receives an acoustic telemetry tag, a small device that emits sound and allows for remote tracking as they swim up and down the coast.
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The research team has tagged 11 juvenile sand tiger sharks since last summer and monitored their movements for up to three consecutive months within Boston Harbor.
The toothy visitors appear to arrive in July and stay until mid-September. As a chill creeps into the air, they begin their southward journey to warmer waters.
By tagging the sharks and recording how many are captured, the team at the New England Aquarium is on its way to getting a population estimate.
The researchers are also interested in better understanding shark behavior, including their preference for the Harbor.
Sand tiger sharks: an overview
The sand tiger shark, also known as the gray nurse shark, is a species found in coastal waters.
It is widely distributed in warm temperate waters to tropical coastal seas, excluding the central and eastern Pacific.
It is known for its distinctive appearance, which includes a robust body and a large, broad head.
The sand tiger shark has a unique dental structure with long, pointed teeth visible even when its mouth is closed.
These sharks are typically found in shallow waters near the coast, often around reefs and sandy bottoms.
Sand tiger sharks are also noted for their reproductive strategy; they exhibit a form of ovoviviparity where the eggs hatch inside the female’s body, and the young are born live.
They are also known to swallow mouthfuls of air at the ocean’s surface, turning their stomachs into air pockets.
Doing so helps them remain buoyant below the surface, enabling them to hover motionlessly as they hunt for prey.
Their conservation status is a concern due to overfishing and habitat loss, leading to efforts to protect and manage their populations effectively.
