NORTH CAROLINA (QUEEN CITY NEWS) – Fascination or fear?
We all seem to have awe for sharks; for North Carolina, it’s something special.
The state is home to the most comprehensive shark study in the country!
The shark tagging vessel teaches us how our rapidly changing oceans impact one of nature’s most feared marine animals.
Captain Stacy Davis and his team have been taking UNC researchers at the Institute of Marine Sciences on the waters for the past 50 years.
Marine zoologist Dr. Frank Schwartz started collecting data on fish and sharks in the late 60s, officially beginning the shark survey off the Carolina coast in 1972.
That makes it the oldest, longest-running shark study in America.
Now, marine ecologist Dr. Joel Fodrie is at the helm.
“The fish don’t read our textbooks, so they kind of do what they want to do; we’re still trying to collect enough data to rewrite the textbooks,” he explained. “Three or four decades ago, you might have a mix of things like duskies and sandbars, and these are 5 to 7, even 8 foot long sharks…blacktips, you see the occasional tiger shark, the occasional bull shark.”
He continues the survey of sharks in the open Atlantic every two weeks from April through Nov.
“It’s much more dominated by three-foot-long Atlantic Sharpnose sharks now, and then every now and then you see some black noses,” he said.
The changes are more accessible to track with 50 years of data.
“Our funding cycles are typically two-year grants, three-year grants, so it’s very rare to have a program that’s been sampling over 50 years,” Dr. Fodrie explained.
So rare that these researchers lovingly call this data the “unicorn” because the consistency in the process makes it even rarer.
Every year for the last half-century, UNC researchers have taken the Capricorn out to sea in the same spot. The 48-foot-long research vessel is equipped with lines, hooks, and a lot of character.
This crew leaves at 7 am sharp to go deep into the open Atlantic off the coast of Shackleford Banks in Carteret County.
A few miles in, it’s time to crank the line and drop the net.
“How do you know when you got fish?” we asked the crew.
They laughed, “when you pull the net up… that’s the only way we know.”
Plenty of fish plopped onboard; the passengers get sorted and hooked, and about 80 to 100 fish hang on the line that zips out and gets dropped into the ocean. The line trails the boat for about a mile.
Then after an hour, it’s time to reel them in. The sharks are on board for less than 2 minutes while a researcher jots down some stats. They mark species, fork length, total length, the sex so, male or female, and the tag number for those released.
Part of the data comes from simple spaghetti tags; Dr. Fodrie explained, “it’s a little plastic tube that has our phone number, our email, and it has a unique number for that tag.”
The information is crucial to the process.
“So when we release that fish, if that fish swims around, maybe stays here, or maybe goes north and someone else catches it, that individual can call us and say, ‘hey, I caught this shark with this tag number in Virginia or right in the same place where we released it,'” Dr. Fodrie said.
The phone rings with that call about four or five times a year, Dr. Fodrie explained, “and so over years and years and years of these tag returns, we can start to figure out where these sharks move seasonally.”
Other data comes from under the microscope, “we have some in the collection; they’re dead and preserved, but they’re pretty charismatic,” Dr. Hughes laughed.
Dr. Lily Hughes is a fish geneticist at the North Carolina Museum of Natural Sciences.
In 1996, the museum acquired pieces from Dr. Frank Schwartz’s original shark survey; Dr. Hughes explained, “it’s been incorporated into our larger fish collection at the museum.” It includes preserved fish, field notes, and journals, “we have 1.4 million specimens. His collection contributed about 200,000 fish specimens — sharks, all kinds of fish from these kinds of trips.”
Today the records act as an immense database for researchers, “back when Frank Schwartz started this survey, and back when the museum started; they didn’t know about DNA, they didn’t know how to preserve organisms for the DNA. We know more now,” she explained.
They add new samples of fish tissues from shark trips like these for genetic analysis; Dr. Hughes said, “we have a minus 80-degree Celsius freezer, and it has about 5,000 fish tissue samples that we can extract DNA from.”
While sharks tagged and released tell a valuable story, “we can learn about how populations are connected to each other, learn about how they’re not. We can learn about new species that are genetically distinct from things that look pretty similar,” Dr. Hughes said.
The DNA of sharks under the microscope can help fill in the blanks.
“If we have this long record of DNA, we can look at whether there are changes to populations over time,” Dr. Hughes explained. “We can look at maybe a population disappears, and the only genetic data we have left of it is what’s in the fish collection.”
Diversity in species type has been one of the most significant changes observed over this 50-year study; Dr. Fodrie notes, “in the first 20 years of the survey, there were a lot of duskies, sandbars, silkies, some bull sharks, and some tiger sharks.”
On our one day out, we caught about 30 sharks, all the same, small three to four-foot sharks known for a long, pointy snout.
Dr. Fodrie reacted, “in the mid-80s, on through the 90s and early 2000s, it really shifted to a lot of sharpnose sharks, and blacknose sharks, they’re much smaller sharks.”
Much smaller sharks are the trend across all species; Dr. Fodrie explained it’s mainly because of fishing pressure.
“Some fisheries, either because of gears or management, can target big individuals,” Dr. Fodrie said. “It just takes time to grow big individuals, and so if you’re harvesting at a certain rate, you never allow any individual to grow to be very big.”
These pressures are only starting to ease some after decades of overfishing fueled by fear from the movie “Jaws.”
Some of these species also respond to summertime water temperatures; Dr. Fodrie explained, “25 degrees Celsius appears to be an important breakpoint. When it gets to 25 or above, we have a summer assemblance of sharks: that’s sharpnose, blacknose, blacktips, a few spinners, bonnetheads.”
OCEAN WARMING NC
But over the last 50 years, our oceans have been warming.
Carolina seas have had a two-degree fever in the critical month of Sept. since the 1980s. Dr. Fodrie added, “the longer that we’re seeing those temperatures at 25 degrees C, the longer we’re going to have those particular sharks here.”
This shifts the seasonality of sharks migrating through the Carolinas, “so sharks that used to get here in early June, may now be showing up in May, and sharks that used to pass by in September, might not pass by now until the first or second week of October.”
This can have trickle-down impacts across the food chain since different sharks eat different things.
“It’s very hard to document all the ways that sharks affect an ecosystem because they’re big, highly mobile kind of diffuse animals that we don’t get to take into the lab and observe in the same way,” Dr. Fodrie added.
This is why the longevity of this study is so crucial.
“Every interaction with a scientist and a fish, that’s data, that’s a story about where you collected it, what the conditions were like when you collected it, and if you keep doing it over time, you see changes,” Dr. Hughes reflected.
Some sharks can live up to 20 years, and their impact at home can be complex, so their story is long.
“You can’t really figure out how populations are changing in two or three years or even eight years or even 15 years,” Dr. Fodrie said.
Just as powerful as they may look, their story can be vital to rediscovering our rapidly changing oceans.
“Which is why we hope to stay out here as long as we can, for decades or even centuries, we’ll see,” laughed Dr. Fodrie.