Warming Waters Bring New Marine Species to NC, But Chase Away Some Familiar Ones

Aug 8, 2017

Bull sharks and lion fish are among the species becoming more common in North Carolina, while black sea bass and other fish are getting harder to find.

You won't see it if you visit North Carolina's coast this summer, but there will be a life-and-death drama playing out all around you, beneath the surface of the Atlantic and the sprawling sounds.

The effects of climate change on marine life are accelerating, and there are few places in the world where that's more obvious than North Carolina, which has an unusually diverse collection of aquatic species.

The state's warming waters have triggered an unpredictable game of musical chairs for marine species, with some heading north for cooler water, some showing up for the first time, and still others getting more common.

In recent years, for example, the lion fish, an invasive species native to the Pacific that has venomous spines, has moved into the state's waters and has become a dominant predator in some places. And one study documented strong populations of Florida stone crabs in parts of the Pamlico Sound, well north of where scientists expected to find such densities of them.

Dangerous sharks move into N.C. waters

Also on the Pamlico, Charles Bangley of the Smithsonian Environmental Research Center in Maryland has been doing research on the bull shark.

It's one of most dangerous species to humans and has been blamed for many attacks in recent years. Bull sharks are large, aggressive, and often swim close to the beach.

Charles Bangley pulls in a longline with a baited hook as he fishes for bull sharks on Pamlico Sound.
Credit Jay Price / WUNC

The bull shark's population is down in some places. But on the Pamlico, the number of juvenile bull sharks caught has been increasing. Bangley thinks the species has begun to use the Pamlico as a key nursery, and the reason may be the warming water.

"We've looked at a couple of different analyses, trying to see what kind of environmental factors are associating with it," he said. "There's a little bit going on with salinity, but it seems like the signal that lights up a lot is temperature."

In parts of the sound where scientists have tracked temperatures, the water is perhaps as much as 3.6 degrees warmer than in 1972.

On a recent night, Bangley went fishing for sharks in the Pamlico. He was hoping to find babies - sharks that were born in the previous month.

"That's proof that this is what's called a primary nursery, which is the term for a nursery area where they're actually born," he said. 

He was also on the lookout for older juveniles, which likely were born in the Pamlico last summer.

"Bull sharks in particular seem to show a lot of site fidelity to places where they're born," he said. 

His team didn't catch any juvenile bull sharks on that particular night. But since then, about 80 have been caught. On a single day last month, state researchers caught seven, watched another four or five fell out of their nets, and could see 30 to 40 swimming on the surface.

In contrast, only nine bull sharks were caught on the Pamlico between 1965 and 2011.

Fishermen worry as fish move quicker than regulators

A big reason reason North Carolina is seeing so much change in its marine species is because the state has an unusual variety of them, said Sara Mirabilio, a researcher and fisheries extension specialist with North Carolina Sea Grant.

Near Cape Hatteras, the cold Labrador Current comes down from the Arctic, and the warm Gulf Stream flows up from the Gulf of Mexico.

"We are at the northernmost range for southern species and the southernmost range for northern species," she said. "So climate change at the boundaries will show the most impact."

In many ways climate change is unfolding as the slowest of slow-motion disasters. But fish can move quickly and for long distances when spurred by relatively small changes in water temperature.

Lately they have moved so quickly that fisheries regulations are lagging, and tensions are rising between commercial fishermen based where the fish used to be, and those where the fish have moved.

On a recent day, Mike Ireland's 99-foot trawler "Sharon Nicole" was docked behind a seafood wholesaler in the Hobucken community east of New Bern, just off the Pamlico Sound.

Commercial fisherman Mike Ireland tends the winches that pull in the nets on his 99-foot trawler “Sharon Nicole.”
Credit Jay Price / WUNC

Shrimp season was under way, but he and his crew were repairing one of the massive, powered winches that haul in their nets. It was an especially crucial one, because it reels in the small net they drag to locate fish.

"This is probably the most important tool on the boat," Ireland said. "With this little sample net you can really pinpoint where they're at."

Where they're at. The question that dominates any fisherman's life. And more and more the answer for fisherman like Ireland is, "Not where they used to be."

Like many North Carolina fishermen, he pursues different species up and down the Atlantic Coast as the seasons change.

And in at least one case, he has to chase them farther now.

"The sea bass fishery, they have migrated to some extent to the north," Ireland said. "We were catching sea bass as far down as Norfolk Canyon for 20 years. Now we're having to go up off the New Jersey coast to get sea bass."

Black sea bass have long been an important winter catch for North Carolina trawlers. The fish have been getting a lot of attention lately because they've expanded their range north and are being found in greater numbers off the Northeast U.S. coast.

That has excited fishermen there, because other species they've traditionally relied on, like cod and lobster, have become scarce or have themselves shifted elsewhere, headed for cooler water.

"It's a domino effect," Ireland said. "The Northern states, they're hurting right now, and their boats are trying to target whatever species the government will allow them to target."

And they want to catch more of the black sea bass that North Carolina fisherman now have rights to. Fishermen in North Carolina have one of the biggest federal quotas of the fish, but politicians and fisherman in the northeast want larger shares for their states.

This week, officials who manage U.S. fisheries north of Cape Hatteras are expected to discuss whether to start a lengthy process that could lead to quota reallocations.

If the North Carolina share is reduced, it may no longer be profitable to steam north for the fish, Ireland said, and profits could eventually vanish for fisherman here, as they have for some fishermen in New England.

"I'm really scared, because New York has their senators behind it. Rhode Island, Massachusetts, they have their senators behind it, and if we don't really don't get to pushing back a little bit I'm truly afraid we're going to lose this fishery," Ireland said. 

Which would shift the fishermen's misery south as the fish move north, Ireland said, because North Carolina doesn't have any fish moving from the south in that would be a good replacement.

"Two degrees is so crucial"

Scientists at East Carolina University, UNC-Chapel Hill, and elsewhere have been developing more elaborate models of how the many intricately-connected parts of an ecosystem are likely to respond to changes like warming waters.

Sara Mirabilio with North Carolina Sea Grant says climate change models haven’t yet been seriously incorporated into fishing regulations.
Credit Jay Price / WUNC

That could help predict not just where a fish that needs warmer water might move, but where others would go if, say, their food source responds to temperature changes.

But Mirabilio, the fisheries extension specialist, says such models haven't been seriously incorporated into fishing regulations yet.

"I'm seeing a lot of science that's starting to document the changes, but I'd like to see them just do some policy modeling," she said. "What do we do in light of this? How do we adaptively manage?"

She conducts her research in collaboration with fishermen, who have begun to include climate change among the long list of challenges they face --alongside such familiar concerns as fuel prices, crew turnover, and complicated government regulations. 

"It's hard for them to think beyond three to five years," Mirabilio said. "They don't want to talk about ten years from now because they don't even know how they're going to feed their family one year from now."

Many commercial fishermen are conservative and don't like to use the phrase "climate change." But Ireland knows what the data say. Not that he needs scientists to tell him what's going on.

"In my 35 to 40 years of going in the ocean, to the best of my a lot knowledge I've seen about a two degree change in the water based on year-to-year, month-to-month," Ireland said.

"Two degrees sound so minimal, it sounds like nothing," he said.  "But to fish I can only assume that two degrees is so crucial."