Very quickly, the scene on the R/V Garvin had turned from research to rodeo on the sparkling Biscayne Bay.
It all started when the drumline grew taut, its thick monofilament stretching from the 55-foot boat into the seafoam-green water. Catherine Macdonald, an environmental scientist and research assistant professor at the University of Miami, worked arm over arm to tug the line closer. Slowly, an eight-foot nurse shark appeared from the depths — a sepia-brown fish with beady eyes, whisker-like barbels and a puckered mouth for sucking prey from the sea floor.
It would be the biggest catch of the day. But it refused to yield, stubbornly fighting Macdonald’s attempts to steer it onto an underwater platform on the research vessel’s stern. Before the shark could spit out the bait and flee — as a would-be catch managed to do earlier on the trip — another UM researcher lassoed the creature behind its pectoral fins with a hefty cable. The team guided the shark onto the platform.
FLORIDA’S 8,400 MILES OF COASTLINE are ripe with shark research and shark-focused tourism, which contributes more than $221 million to Florida’s economy.
In a last-ditch escape attempt, the nurse shark writhed in a flash of fins and fury. That’s how Macdonald found herself leaping onto the predator, holding its head in place with a bearhug as it bucked like a bull. Another researcher rushed to help secure the fish, then another, then another. At the fifth aide, the shark surrendered — the next reluctant participant in the UM Shark Research and Conservation Program that Macdonald directs.
Sharks first appeared in the fossil record 450 million years ago. (Modern humans, in contrast, entered the scene only 300,000 years ago.) They’ve since survived five major mass extinctions, including the event that wiped out dinosaurs 66 million years ago. The number of known shark species exceeds 500 — ranging from the largest fish in the world, the 60-foot whale shark, to the smallest shark, the seven-inch dwarf lantern shark, to the longest-living vertebrate, the 250-plus-year-old Greenland shark. Their evolutionary success, adaptation and diversity make them ecological marvels.
With 8,400 miles of coastline, it’s no mystery why Florida has turned into a hub for shark research. Dozens of species roam the state’s warm waters, creating one of the most diverse shark concentrations in the world. It’s enough for shark-based tourism to contribute more than $221 million and 3,700-plus jobs to Florida’s economy, according to a 2017 study by nonprofit Oceana. The year-round abundance also gives scientists ample opportunities to study the predators in their natural habitats. The resulting studies — which have proliferated within Florida institutions over the last decade — lend clues about our oceans as well as seemingly distant industries, from health care to STEM education.
“It’s mysterious to me that more people aren’t interested in sharks. Just really fascinating life forms. Persistence is their middle name. How have they managed to last for very long?” asks Gavin Naylor, director and curator of the Florida Program for Shark Research at the Florida Museum of Natural History. “They’ve got some kind of tricks, and I think that we’d like to find out what those clever tricks are.”
CURRENTS AND CLUES
The eight-foot nurse shark was one of five sharks Macdonald’s team landed that day. The smallest catch, a full-grown bonnethead shark, only stretched 31 inches.
The researchers led each finned patient through a quick workup. Syringes sucked blood samples to monitor stress, diet and hormones. Tape measurers ran the length and girth of each animal. Mature females received an ultrasound. Vigilant eyes searched for parasites. Careful hands collected tiny tissue samples for genetic testing. The last step: securing an identification tag on each shark’s dorsal fin before freeing them back to the bay, their sleek bodies wriggling into the blue unknown.
There, within marine ecosystems, sharks play vital roles. Many species mark the top of their food chains, regulating prey populations and recycling nutrients. They feed on herbivores that would otherwise chow down on marine plants, which sequester carbon through photosynthesis, preserving important underwater habitats like kelp forests and seagrass meadows. The predators tend to target weak or sick prey, weeding out the feeble and strengthening overall fish populations.
Ocean health depends on sharks, so it’s important to monitor their populations. That’s where tagging and tracking come into play. Techniques run the gamut.
The tags used by Macdonald’s team help identify sharks if they’re caught again, allowing researchers to learn about their growth and movement between captures. Specimens in other projects may get satellite or acoustic tags that transmit their locations to scientists ashore. Biologging tags, acting like FitBits, can track shark behaviors like foraging, mating and resting to better understand their ecological roles. There are also camera tags that temporarily attach to sharks’ dorsal fins and, upon retrieval, provide video insights.
Altogether, Florida tagging initiatives have marked sharks near and far. Some schools focus on sharks in their local waters, like Florida State University’s work among the Big Bend seagrass habitats. Macdonald’s UM lab primarily focuses on sharks in Florida waters. Her team was the first to describe a great hammerhead shark nursery in Biscayne Bay, the only one identified on the East Coast. Other institutions, like Nova Southeastern University, have tagged sharks around the world, from Maryland to Australia to the Galapagos Islands. (The school’s tracked species include the shortfin mako shark, NSU’s mascot.)
Their findings can be sobering.
Demian Chapman, a Florida International University adjunct professor and director of the Mote Marine Laboratory and Aquarium’s Center for Shark Research, leads the world’s largest reef shark and ray survey. (Rays and skates are close relatives of sharks and are often researched in concert.) Called Global FinPrint, the project relies on baited remote underwater video systems that monitor more than 400 reefs around the world. Research partners across 58 countries dropped GoPro-like cameras in a reef, pulled them out after an hour, and then counted the sharks and rays captured on the video feed. The snapshots check the pulse of global populations.
The first phase of Global FinPrint took more than 1,000 volunteers to watch 20,000-plus hours of video footage. The team didn’t detect sharks on 20% of surveyed reefs, signaling depleted reef shark populations in most nations around the world. Other studies show similar declines. A 2021 international analysis showed that, since 1970, the global abundance of oceanic sharks and rays has dropped by 71%, threatening three-quarters of the species with extinction.
It’s not all doom and gloom. FinPrint found several “reservoirs of hope” where sharks are still relatively common and could help repopulate other areas if given the chance — a chance made possible because of shark research.
“FinPrint is our on-the-ground — on-the-water — bottom-up work to achieve conservation, and that’s really critical,” Chapman says. The project’s second phase is now underway, returning to 100 reefs across 30 countries to see how shark populations may have changed and why.
Any data about sharks helps guide local, state, federal and international policies that better protect the predators and their habitats. One popular conservation measure is a marine protected area, where human activities are restricted to conserve ocean life. Pinpointing shark hotspots can optimize the impact of such protections. Florida waters alone host more than 40 marine protected areas.
Shark research also helps scientists better understand how other threats — like habitat loss, poor water quality and climate change — are affecting species. Many of these hazards originate in our own communities.
“People tend to think about nature as something that’s far away in this pristine place that is untouched by man and that should be protected,” says Julia Wester, who researches social-ecological systems as a UM senior lecturer and directs the school’s ecosystem science and policy undergraduate program. “But nature is trying to make a go of it right here, right next to us. Our goal is not to make this untouched, but to do our part to be good neighbors.”
HOOKED AND HUNTED
Perhaps the most well-known threat to sharks is the international fin trade.
Shark fin soup, a delicacy in Chinese cuisine worth upwards of $100 a bowl, rose in popularity in southeast Asia during the late 20th century. Fin values spiked as demand skyrocketed. The international fin trade bloomed in response, giving way to unsustainable and inhumane practices like finning. Fishers would cut the coveted fins off live sharks and throw their bodies back into the sea, where they’d sink to the ocean floor and die. Miami once marked the U.S. gateway for imported shark fins.
The shark fin trade used to be an unregulated free-for-all until a 2006 NSU study quantified, for the first time, shark mortality within the global industry: Up to 73 million sharks fell victim to the market per year, a number four times higher than previous estimates. Most of the sharks belonged to at-risk species, additional studies found.
Mahmood Shivji, the paper’s senior author and the director of the NSU Guy Harvey Research Institute & Save Our Seas Foundation Shark Research Center, is a pioneer in using genetics to learn more about the shark fin trade. He collects fin tissue samples and identifies their species based on their DNA. He can also trace samples back to their origin using genetic signatures specific to regional shark populations.
Mote’s Chapman has also been entrenched in studying the fin trade. Since 2014, his team has monitored Hong Kong’s fin trade every year — which has long reigned as the global epicenter of the industry. (An FIU colleague developed a PCR test, similar to those used during the COVID-19 pandemic, that helps customs workers discern shark species in fin shipments.) All findings are fed into assessments for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES. The international agreement helps manage wildlife trade to prevent extinction, assigning different levels of regulations for at-risk species.
CITES identifies species that could face extinction without trade controls, and it implements an international permitting system for them. The number of shark and ray species listed under that appendix has risen from seven to more than 150 since Chapman started his work. More than 90% of shark species found in the fin trade are now protected under CITES.
“It’s a huge chunk. It’s a complete sea change,” Chapman says. “The great thing about CITES is that it actually has teeth by itself. ... We are constantly feeding information to (CITES) about this illegal trade of sharks, and that then triggers these actions against the illegal trade.”
FLORIDA RESEARCHERS ARE studying the international fin trade, which is among the biggest threats to sharks. Shark fin soup, an Asian delicacy, can fetch upwards of $100 a bowl.
Policy changes around the world are targeting the international fin trade. Finning is now banned in most countries. The U.S. prohibited shark finning in all federal waters in 2000, and a 2022 law further clamped down on the shark fin market by banning fin trade.
Another threat has come into focus: unsustainable commercial fishing that can entangle and kill sharks — intentionally and unintentionally. A 2021 study estimated that fishing-related shark deaths have climbed up to 100 million each year. Some cultures, including countries in Latin America and Europe, are churning up demand for shark meat as the fish of their typical cuisines grow scarcer with overfishing. Sharks’ own menus are impacted as their prey populations suffer.
In a 2017 NSU study on shortfin makos, satellite tags revealed that about a third of the 40 tracked sharks were captured and killed in fisheries — a mortality rate 10 times higher than previously believed. “We were very disappointed because it’s an interrupted journey, like you’re messing with our work,” says Shivji, the paper’s senior author. “For those of us who are in the conservation business, we kind of go, ‘Jesus, you have no idea what you’re destroying.’” (His findings led to a 2022 U.S. ban on killing shortfin mako sharks.)
Florida is a growing powerhouse for recreational fishing, which poses another conflict for sharks.
Instances of depredation, when sharks steal fish off lines, have increased. A February study from Florida Atlantic University found 43% of surveyed anglers experienced depredation, the probability increasing to 60% due to regional and seasonal variations.
“I’m sympathetic, because those inconveniences can be really frustrating. But at the same time, inconvenience should not be used as an ecological metric,” says John Hlavin, a UM Ph.D. student in Macdonald’s lab studying shark diets. “We need to come up with a way to forward both recreational fishers’ interests and promote ecosystem integrity. We have to find a balance between those two things.”
Some anglers claim sharks are now overpopulated, citing a “shark explosion” and equating them to “cockroaches,” Chapman says. In reality, it’s a case of shifting baselines: Today’s fishers weren’t exposed to healthy shark populations of a century ago. As populations recover from overfishing, compete for fish and interact with fishers more, it creates the illusion of shark abundance — when really, many species are still hanging on by a thread. Researchers are studying shark deterrents, like electric pulses or magnets, that could decrease depredation.
Still, resentment against sharks — and even retaliation — isn’t unheard of. Some anecdotes place fishers just outside protected waters, waiting to intercept and kill sharks. This June, a Florida Keys charter captain was arrested for repeatedly stabbing a bull shark for breaking his fishing rod. A 2019 video shows a Naples fisherman shooting a shark with a pistol. A shark fishing tournament in 2022 in Palm Beach County drew criticism for killing at least nine sharks.
A BIOMEDICAL BLUEPRINT
Shark mating can be a gory affair. Male sharks must bite their partners to get them into position, the pair thrashing in a fight for dominance. The resulting wounds, even very severe ones, tend to heal rapidly and without infection — an evolutionary novelty.
It’s one reason some cultures eat sharks, hoping to glean their uncanny healing abilities. The superpower, along with other fishy features, has also sparked scientific interest in translating shark research into human health breakthroughs.
Carl Luer has worked at this intersection for more than four decades at Mote, using sharks, skates and rays as animal models for his biomedical research.
With the Department of Defense, he has investigated how stingray mucus could be key to developing antibiotics for resistant pathogens. His team is looking to stingray venom for clues about drugs, pain and blood pressure. He’s also tried — unsuccessfully — to induce cancer in sharks. (Counter to popular belief, sharks actually can get cancer, but it’s rare.) While the carcinogens reached the target sites, the affected DNA was repaired rapidly. Now in retirement, Luer is still helping that project uncover how compounds derived from shark immune cells inhibit human cancer in the lab.
Researchers are sequencing the genomes — or all the genetic information — of sharks to decode how their biology created such adaptations.
NSU’s Shivji, for instance, was the first to sequence the genome of white sharks in 2019. He found that they have very stable genes and develop fewer mutations than humans. That’s because they have better mechanisms to repair mutated DNA, leading to less incidence of harmful diseases like cancer and neurological ailments. Shivji also identified a higher proportion of genes related to wound healing compared to the human genome. Other shark species, like whale sharks, share similar genetic qualities.
SHARKS HAVE A REMARKABLE ABILITY to quickly heal from significant wounds. Researchers hope to translate their uncanny healing abilities into human health breakthroughs.
“Sharks have had a long time to evolve adaptations to keep them around, keep them successful,” Shivji says. “One assumes that is the reason you see these higher proportions of genes that keep them around in this extremely long evolutionary history.”
Applying such findings to human health innovations is in its infancy. Some are slowly entering the marketplace, like Sharklet Technologies. The UF startup, now based in Colorado, drew inspiration from shark skin to create the first surface technology that inhibits bacteria growth via pattern alone. The company sells products like catheters and endotracheal tubes that are adorned with the distinct diamond pattern.
But Luer says it’s a big leap to jump from basic research to human applications, one handicapped by a lack of funding for the nontraditional medical approach. Others, like Naylor from the Florida Museum of Natural History, call it an “optimistic story that lacks data to support it.”
NSU — in particular, its new chief medical officer Dr. Chad Perlyn — is itching to dig deeper.
This year, the university is launching its NSU Ocean Health Initiative to combine its core research areas — marine ecology and health care — and pump out translational science that could be the foundation for clinical trials, medicinal cures and technological innovation. Identified projects include topics like microplastic impacts, undersea medicine and shark immunology research.
“If we do not have healthy oceans, we will not have healthy people,” Perlyn says. “The amount of interest and attention being brought to this is on an exponential curve.”
STEM WITH TEETH
Back aboard the R/V Garvin, once the nurse shark surrenders to the research team, Macdonald carefully unwinds from her bearhug and repositions herself on the underwater platform. She now faces a very captivated audience: a collection of Girl Scout troops from Tampa Bay.
There is no John Williams score playing, no duuuhh-nuhs from the iconic Jaws franchise that sparked shark mania 50 years ago. Instead, tweens speak with hushed excitement. Throughout the day-long tagging trip, they’ve helped set, reel and reset 30-plus drumlines. They even take turns assisting with the research, calling out measurements and tag numbers and parasite checks for each specimen aboard. (This group of guests also distributes shark gummies after each successful landing and names every caught fish. Meet Nelson, the eight-foot male nurse shark.)
“This was the defining moment,” announces Ellee Kluis, a 13-year-old Girl Scout from Palm Harbor, late in the day. “Marine biology has always been (near) the top of what I want to do when I grow up. ... Now it’s higher up.”
The sentiment is enough to put a smile on Macdonald’s sun-screened face. Through the UM Shark Research and Conservation Program, she brings between 800 and 1,000 middle and high school students shark tagging each year. She is also the co-founder and director of Field School, a program offering hands-on marine science research experience. Its mission? Offering introductory field work amid supportive and inclusive learning environments. Across both programs, Macdonald’s teams are in the field around 115 days a year doing just that.
Once the nurse shark is released, a Girl Scout gushes to Macdonald about her feat. Macdonald responds with a fist bump. “When we have all-girl groups,” she later says, still drenched from her dip in the seawater, “it’s important to show that it’s not just the boys that do the heavy lifting.” Research has shown many girls lose interest in STEM fields around age 15.
Macdonald hopes sharks — large charismatic creatures with even larger reputations — can be a gateway to STEM fields. Others do, too. NSU has whisked more than 6,800 participants on shark science expeditions since 2014. UM is home to the Females in Natural Sciences (F.I.N.S.) initiative, which provides girls with hands-on experiences in women-led marine sciences. Minorities in Shark Sciences, a Bradenton-based nonprofit founded in 2020 by four Black female researchers, provides accessible and inclusive pathways to research, conservation and education in marine sciences. The Coastal Marine Education and Research Academy in Clearwater is one of several organizations that offer paid programming with sharks, designed to give students experience in their chosen field.
The high-touch, safe experiences also counter the popular narrative that sharks are human-hunting monsters.
If anything, the number of shark attacks around the world is slightly declining, says Naylor, who heads the International Shark Attack File — the world’s only scientifically documented, comprehensive database of all known shark attacks since 1958. There were only 47 unprovoked attacks in 2024, down 22 from the previous year and well below the 10-year average of 70. Seven were fatal, four of which were unprovoked.
Florida saw 14 shark bites last year, more than any other state, and a third of the world’s total bites. Volusia County — the colloquial “shark bite capital of the world,” home to popular beaches like New Smyrna and Daytona — reported eight bites. None were fatal.
All the while, the number of human hours in Florida waters has increased thanks to population growth and tourism. Yet the number of shark interactions has remained very low and stable.
“I tell people that if sharks targeted people, we’d have about 10,000 bites a day,” Naylor says. “The fact that there’s so many sharks in the water and so many people in the water, and there’s so few bites, tells me that sharks are doing their best to avoid people. Occasionally, when they do bite them, it’s because the water’s murky and they made a mistake.”
Shark Doctor
Dr. Robert Borrego chuckles at his “Shark Doctor” nickname. But the West Palm Beach trauma surgeon can see why the title stuck.
Since 1991, Borrego has worked at the St. Mary’s Medical Center, which sees five to six shark bite patients a year on average. (He famously helped save the leg of shark-diving pioneer Erich Ritter, who was attacked by a bull shark while filming a Discovery Channel interview for Shark Week in 2002.)
The first step after a bite: Stop the bleeding and stabilize the wound. The second step — just as important — is making sure that wound heals by preventing infection. Historically, doctors would pump broad spectrum antibiotics into victims, a “shotgun approach to kill anything and everything.”
During a toddler’s visit to the hospital due to a bite in 2012, when the father asked about the types of bacteria in shark mouths, Borrego confessed he didn’t know. The line of questioning became a side project. He started fishing for sharks on beaches and by boat. Once they were reeled in, Borrego would disarm them by rubbing their snouts, stimulating the sensory endings there and rendering them immobile. Then he’d swab their teeth and gums, bring the samples back to the lab, and grow the bacteria in incubators for study.
Borrego has since catalogued more than 50 sharks and the bacteria in their mouths. He found that the type of bacteria varied by species and by shark location. Sharks found closer to the shore, for example, had different bacterial properties than those in the open ocean. The knowledge helps doctors cater specialized antibiotic treatments for each shark bite victim.
“By having that discovery, we minimize the side effects, and the patients do better,” Borrego says. “They have a shorter hospital stay, and they go home sooner. We could even treat them at home with specific antibiotics.”
Tips to reduce risk of shark attack
- Swim with a buddy.
- Stay close to the shore.
- Don’t swim at dawn or dusk, the most active feeding times for sharks.
- Don’t swim around schools of fish — sharks’ prey — or where people are fishing.
- Avoid wearing jewelry. The light reflecting off metal could resemble the glint of light off fish scales.
- Avoid excess splashing.
Source: University of Florida’s International Shark Attack File