Is Crystal River a nursery for baby bull sharks? We went fishing to find out.
CITRUS COUNTY — Just 12 minutes had passed since the bait hit the water.
The tide flowed into the Gulf of Mexico, and each passing minute dropped the pontoon closer to Crystal River’s rocky bottom. Five chunks of ladyfish floated on hooks: Three on a handline, two on rod-and-reel.
A handline was hit first.
“Shark!” yelled Alyssa Andres, a postdoctoral fellow at Florida State University’s Coastal and Marine Laboratory.
“That’s a shark!”
What happened next is best described as a blur.
In just six minutes, a team of four researchers brought the young female bull shark aboard, tagged her dorsal fin, weighed her (nearly 10 pounds), measured her (2 feet, 10½ inches), aged her (born within the past year) and took blood and muscle samples.
In a flash, the shark was kicking away from the boat and scientists cheered with whoops, high-fives and smiles.
This would be the first of five baby bull sharks caught and tagged on a recent scientific fishing trip in Crystal River, a spring-fed waterway that sprawls for 7 miles through Citrus County.
The river is known worldwide for the hundreds of manatees that gather each winter near the outflows of the river’s springs as they seek the warmth of water that is 72 degrees Fahrenheit. Could cold-sensitive bull sharks be doing the same? Are mother sharks relying on the temperate springs to birth and shield their young?
The answer to that research question could better inform how humans protect sharks and habitats like Crystal River in a future where climate change may alter shark behavior. It also could offer a key to springs restoration and shark conservation in estuaries like Tampa Bay, where bull sharks are known to feed and give birth.
Andres and her team of researchers on the newly minted Crystal River Bull Shark Project started fishing for sharks in August and began tracking their movements two months later.
Since the team began, they have caught 27 baby bulls and are monitoring 10 of them with special acoustic tags that map where in the river a shark has traveled.
“The biggest threat to bull shark survival is loss of nursery habitat, because this is when they’re most vulnerable,” Andres said, pointing to the river around her.
“As their coastal habitat degrades because they rely on rivers and estuaries — which obviously are also heavily influenced by humans — they are losing their ability to shelter their babies.”
At full maturity, bull sharks can grow to 11 feet and are estimated to live more than two decades. Bull sharks are one of the few shark species known to inhabit freshwater ecosystems, and there’s even documentation of them venturing hundreds of miles up rivers, according to Florida’s wildlife commission. Their preference of shallow coastal waters and their ability to thrive in freshwater make their encounters with humans more likely.
In estuaries like Tampa Bay, mother bull sharks will typically leave the nursery right after giving birth, and it’s likely that’s also happening in Crystal River, according to Andres.
In many ways, the bull shark project is personal. Harrison Clark, the project’s lead field technician, is from Crystal River. The team is using his family’s boat for the research fishing trips. And he’s been dating Andres for the past four years.
The idea for the research was born during Thanksgiving dinner in 2021, when Andres was at the Clark family’s house. From inside the waterfront home, Clark saw that anglers a few hundred feet away had hooked into a shark. Soon Andres — who studied sharks for her doctorate in marine science — was outside yelling questions to the anglers about the animal’s size and weight.
Clark remembers telling Andres that night: “I’m from here, and you’ve studied bull sharks. Let’s do a project.”
Soon the team had scored a $10,000 grant and was laying the foundation for what would become the Crystal River Bull Shark Project.
“It’s been really taking off,” Clark said. “Which is so great.”
A community effort
The shark research team wasn’t able to launch the boat in December — but they had help.
A key part of the Crystal River Bull Shark Project is its encouragement of citizen science. Andres and her team are asking local anglers to report their bull shark catches, including when and where the animal was caught.
On Dec. 14, an angler provided photos of two bull sharks he caught in Kings Bay, an enclosed estuary that supplies 99% of the fresh water within the river system. He caught and released the pair 10 minutes apart while he was fishing for ladyfish. That data was crucial for the team that couldn’t be on the water, and the angler report filled a knowledge gap that now confirms bull sharks are still swimming in Crystal River at the end of the year.
Having community members involved in the project builds a fuller picture of bull shark habits when researchers can’t always be on the water, and it introduces anglers to the world of marine science, Clark said.
“We didn’t want to come in, do the science under the radar and leave,” Clark said. Crystal River, after all, is a community his family intimately knows: His mother has owned an audiology business for three decades and is spreading the word about her son’s ongoing shark project at her regular Rotary Club meetings. It’s built community trust.
“It’s a lot more work, but the benefit is that it helps us and gets the community involved,” Clark said.
The biggest shark yet
Stephanie Perez, an intern with the bull shark project, was chatting on the boat’s port side about what drew her into the world of shark science, when suddenly …
“We’re running, we’re running!” Andres yelled, the whiz of a fishing rod forcing everyone on the boat out of their seat.
The crew had ventured upriver toward Bagley Cove, close to King’s Bay. It was just past 11 a.m. when they hooked into the third baby bull shark of the day.
And this one was a doozy.
“111 centimeters,” yelled Isabella Pino, the second intern on the boat.
“That’s the biggest one yet!” replied Perez.
Not every bull shark the team catches gets an acoustic device, because the process to insert it requires a small incision in its belly. The sharks have to be full of energy when they reach the boat, to make sure they can swim off with strength. There was no doubt about this one, though. At a healthy 19 pounds, he checked all the boxes.
Andres cut a small, inch-long incision on the bottom of the shark and slid a cylindrical acoustic monitor through the cut. This device, Andres explained, will give scientists a granular view of the shark’s movements as soon as it returns to the water. A series of “checkpoints” are scattered around the river that will catch and record the pings coming from the shark’s monitor.
“You’re OK, buddy,” she told the shark. With the grace of a surgeon or a seamstress, Andres stitched the animal with sutures. She had been perfecting this procedure with a practice surgical kit she bought in November. This was the 10th shark surgery since.
“That looks beautiful,” she said, turning the shark back over. “I am so happy with that.”
The team watched as the shark kicked back into the murky depths of Crystal River. Each member breathed heavily as the whirlwind of another catch-and-release had come to an end.
The project has a handful of collaborators, including the nonprofit group Minorities in Shark Science, which is providing funding for the two internships (a rarity in marine science education).
The $10,000 for the project’s 15 acoustic tags, an acoustic recording device and a machine to spin shark blood for sampling came from the Fish and Wildlife Foundation of Florida, which raised the money by selling the “Protect Florida Springs” license plate.
The foundation chose to fund the research because it could reveal yet another reason why Florida’s springs systems are so crucial for life in aquatic habitats, said Michelle Ashton, a spokesperson for the group.
The research could also underscore how humans are changing natural spring flows, and how that may be detrimental to shark populations — let alone scores of other marine species relying on springs.
“These are good people doing good work,” Ashton said.
“I’m really inspired by the team doing this on their own time, out of their own quest for knowledge, their passion for sharks and for a better understanding of these ecosystems.”
Funding is still needed for the Crystal River Bull Shark Project. If you’d like to contribute to the cause, the team suggests emailing crystalriverbullsharks@gmail.com
