FORT FISHER — The Cape Fear region attracts all different types of migratory behavior, from geese in the winters, part-time residents with vacation homes, and countless aquatic species. But researchers at the North Carolina Aquarium at Fort Fisher are now thinking it could be the full-time residence for sand tiger sharks.
The Aquarium at Fort Fisher is no stranger to sharks. It cares for and houses several species of sharks, from bamboo sharks to bonnet head sharks–a relative to the hammerhead shark, Husbandry Curator Julie Johnson said.
But there is still little known about the habits of sharks in the wild, especially when it comes to breeding.
Aquarist Madeline Marens said, “Most sharks are highly migratory, so in North Carolina we’re kind of smack dab in the middle of the East Coast so we have a lot of sharks going south to Florida and going north for the summer. But we think that North Carolina is a residency for some of our local sand tiger sharks.”
Sand tiger sharks have been found in large populations in Delaware Bay by researchers, but mature females are not readily found there, Marens said. The observation of mature female sharks off the region’s water’s left researchers thinking the waters of North Carolina could be a full-time residence for the sharks.
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“Sand tiger sharks are a coastal dwelling species, so people from all over the world come (here) to dive with them. They are found in aggregations on shipwrecks. We actually see large mature females here year-round, so it got researchers thinking, ‘What are they doing here?’” Marens said.
Since the sharks are a coastal dwelling species, they are at risk from overfishing and habitation degradation, which is why researchers are trying to learn more about these fish, both to learn more about them and to protect them.
Tracking the sharks
Marens is a masters student at UNCW; the Aquarium at Fort Fisher has teamed up with UNCW to capture and tag sand tiger sharks.
“We are tagging these mature females off our coast, we are outfitting them with electronic tags that have a unique code, so we’re able to track their movements … so far we have tagged 18,” Marens said. “We have North Carolina Aquarium veterinarians on board as well so were ultrasounding these females, and we have had confirmed pregnant sharks.”
The tagging procedure requires minor surgery, in which a tracker is placed subdermally to track the shark’s movements. Trackers have a battery life of about 10-years.
Unlike some of the satellite trackers used on larger and more charismatic sharks, like great white and tiger sharks, the trackers used by Marens do not require the shark to breach the surface of the water. Instead, receivers are placed near shipwrecks and artificial reefs, known places these sharks reside near. From there, they send tracking data when a tagged shark is within the proximity of the receiver.
Although sharks have a fearsome reputation, sharks play a pivotal role in maintaining a healthy ecosystem in local waters. Sand tiger sharks, in particular, are docile towards humans, and people from around the world come to North Carolina to dive with them.
Overfishing and habit destruction can permanently alter the marine ecosystem that millions rely on.
“As top predators, they play a really important role in the balance of healthy ecosystems. They keep fish populations in proportion, if you take that top predator out, you have the potential of that trickle-down effect that would make fish populations unhealthy,” Marens said.
Shark populations are in decline, and part of that is due to fishing, but it is also worth noting sharks take several years to mature to breeding age.
“What makes sharks so prone to overfishing and habit degradation is these species are really slow-growing and late to mature. Sand tiger sharks, for instance, take 9-10-years just to be able to reproduce, and then they are only producing one or two pups at a time, Marens said.
“If we can identify what the mature females are doing and where they are pupping that would be a really important protective measure in helping them rebound,” she concluded.
