Climate change moves bull shark range from Indian River Lagoon to North Carolina

Climate change is allowing bull sharks to move north; but don't worry, says a local shark expert, they won't be leaving the Indian River Lagoon.

The number of baby bull sharks in waters off North Carolina has been increasing since 2011, according to the May 2 edition of Science News.

"Previously, the northernmost nursery for bull sharks ... had been Florida’s Indian River Lagoon," the story states.

"The bull sharks are simply expanding their range," said Grant Gilmore, senior scientist for Estuarine, Coastal and Ocean Science in Vero Beach. "They won't abandon the Indian River Lagoon unless we drive them away by killing the estuary, which looks like we're doing a pretty good job of."

More bull sharks farther north won't mean fewer in Treasure Coast waters, said Gilmore, who's been studying animals in the lagoon since the 1970s.

"Bull sharks are basically a tropical shark found in warm water around the world," he said. "Global warming means there's more warm water for them to expand, not just their range, but their population."

Lagoon nursery

Bull sharks mate in the ocean, Gilmore said, and the females come into the lagoon each spring to give birth.

More: Springtime is shark time in Florida's coastal waters

"The females typically stay pretty close to whatever inlet they came in," he said. "They give birth to anywhere from 10 to 18 pups. It's a live birth; each of the pups will be from 15 to 18 inches long."

After giving birth, the mama shark goes back into the ocean.

More: Mets don't take any bull from sharks

The pups will stay in the lagoon from 5 to 7 years, Gilmore said.

"Actually, they may not stay just in the lagoon," he said. "They can roam around. They've been seen as far inland as Lake Okeechobee, and they get into the headwaters of all our rivers: the St. Lucie, the St. Sebastian, the Loxahatchee."

Bull sharks have a reputation for being aggressive, if not downright mean.

A bull shark is suspected of killing kiteboarder Stephen Schafer in February 2010 near Stuart Beach, the only known fatal shark attack in Martin County history.

More: Kite surfer dies from shark attack near Stuart Beach

It was Gilmore who, based on autopsy photos, said shortly after the attack a bull shark was the only local species that could have left the bite pattern found on Schafer's thigh.

An artificial reef south of the attack site is known as "Bull Shark Barge," Gilmore said, "because so many bull sharks are seen there."

More: Treasure Coast Shark Attack Database

A lotta bull (shark)

Range: Warm, shallow ocean water around the world but can live in brackish water (like the Indian River Lagoon) and can be found in freshwater.

How they survive in freshwater: Kidneys and a gland near the tail prevent loss of body salt in low-salinity water.

Size: Females can reach 5 feet and 500-plus pounds; males 7 feet and 200 pounds.

State record: 517 pounds, Panama City Beach, October 1981.

Appearance: Gray backs, white bellies; fin tips are black, especially in younger sharks; wide snouts and sharp, triangular teeth.

The name: From the habit of butting prey with their heads before biting.

Speed: Usually swim about 5 mph but can reach 12 mph.

Diet: Fish, turtles, crustaceans, dolphins, birds and other sharks.

Humans? Don't normally eat people, but will attack anything that moves in its territory, including humans. Average of 16 attacks on humans each year in the U.S. Fatal attacks average every two years.