Biologists Rescue Unborn Baby Sharks at Fish Markets | Innovation

Biologists Rescue Unborn Baby Sharks at Fish Markets | Innovation

The embryo of a small-spotted catshark, safe inside its egg case, is being raised at the aquarium Oceanogràfic València by Associació Lamna, a nonprofit that promotes shark conservation and research. At this stage, the young shark’s gills are still external and it is growing from the sustenance provided in the yolk, visible at the bottom of the egg case.
Associació Lamna

It’s 3:00 a.m. on the island of Malta, and in the stillness before most residents wake to begin their day, a shark is about to give birth. This is especially strange, not just because it’s happening on land, but because the shark in question is dead.

Surrounded by vendors preparing for the start of their day at the wholesale fish market in Valletta, Greg Nowell carefully runs his fingers along the belly of the shark: a small-spotted catshark, a compact, slender creature only half a meter long, with cream-colored skin covered in a galaxy of black dots. Where the shark’s skin is thin around its internal organs and womb, Nowell presses inward with a finger and feels something rigid and hard. He pushes, gently, encouraging the object back toward the cloaca, the opening shared by the shark’s intestinal, urinary, and reproductive tracts. With a gentle pop, it emerges: a tiny egg case, no longer than Nowell’s pinkie finger, yellowish-brown in color and—though it might not look it—likely still thrumming quietly with life.

Nowell will do this for dozens more sharks before the morning is through. As vendors begin scaling bream and filleting grouper around him, he’ll move between plastic totes, each stacked several layers deep with sharks packed in ice, identifying females and feeling for their eggs. Each egg that he finds is dropped carefully into a container of salt water for transport back to his office. There, Nowell and the team at the organization that he founded, Sharklab-Malta, will try to give each unborn shark another shot at living.

Sharklab-Malta is one of at least three groups around the Mediterranean taking on the unlikely role of nursemaid to several species of sharks and their close relatives, skates. By collecting and raising babies from females that wind up in fishing nets—most often as by-catch—and then on fishmongers’ counters, the groups hope to make a small difference in a world that has not been kind to sharks.


Biologists Rescue Unborn Baby Sharks at Fish Markets

Small-spotted catsharks live in coastal regions of the Mediterranean Sea and the Atlantic Ocean. They are common in the fish markets of the Mediterranean and biologists from Associació Lamna have been retrieving the unborn young from newly caught adult females, in an effort to learn how to raise and hatch the young sharks and eventually release them into the wild.

Gerard Soury/Getty Images

The International Union for Conservation of Nature (IUCN) estimates that more than a third of the 1,147 shark, ray, and skate species in the world’s oceans face extinction. In a widely covered paper published earlier this year, researchers found that oceanic sharks and rays have declined by 71 percent in just the last half-century, primarily due to overfishing—both intentional fishing and unintentional capture by nets and hooks meant for others.

Before the sun’s first rays touch the tips of the palm trees and set the Mediterranean glittering, Nowell will leave the fish market with a handful of new egg cases sloshing in his care. The babies that emerge from them will play two roles: first, they will serve as ambassadors for their kind, teaching kids and adults to see sharks as fascinating, vital, and, hopefully, worth protecting. Second, they will act as guinea pigs, helping refine standardized procedures for raising babies like them. Nearly a decade after Nowell began the first experiments on market-collected egg cases, the scientists working with these eggs hope these methods are ready to be adopted for other species of sharks and skates.

Luckily, an estimated 30 to 40 percent of sharks and all skate species are oviparous: males fertilize the eggs internally, then females unload each growing embryo on the ocean floor enclosed in an egg case. This leathery pouch serves as a little external womb, packed with nutritious yolk that feeds the young shark as it grows.

This strategy is common enough in the shark family that egg cases are frequently found tossed up on beaches, hooked into tangles of seaweed. They’re most often dark brown or black, like an overstuffed leather wallet with a spindly, curling leg on each corner. (Or, in a COVID-19-era analogy: they look a bit like a face mask.) These egg cases are known to beachcombers in North America and Western Europe by the colorful name of “devil’s purse,” or in a less superstitious turn, “mermaid’s purse.”

The egg-case approach is also common enough that the scientists involved hope techniques from the Mediterranean could help species facing a much greater risk of extinction, unlike the relatively abundant small-spotted catshark.

“Some people ask, ‘If you’re taking these eggs and recovering sharks, are you saving the population?’ And we’re not,” Nowell says. “If we can put two back for every one [fished], fantastic. But ultimately what this whole process enabled us to do was look at a methodology, and develop a method that can be used anywhere in the world.”

If there’s one thing that Pablo García Salinas and Jaime Penadés Suay have learned from raising sharks, it’s this: don’t throw the babies.

The two Spanish marine biologists have found that unhatched sharks, nestled within their protective egg cases, are incredibly hardy. They can survive being hauled up from the seafloor, snarled on fishing nets and seaweed. They can survive sitting for hours in a plastic bottle on a fishing trawler, even without refrigeration. (The scientists tried giving the fishermen that collect egg cases for them buckets of ice for the eggs, but they just used it for beer.)

What they can’t survive: the acceleration of being tossed by a fisherman from his ship to the dock, to land clumsily in García Salinas’s hands.

“Those eggs never developed,” Penadés Suay says glumly over a video call. “We tested maximum velocity, and it’s not good.”

Nonetheless, in less than two years, García Salinas and Penadés Suay have raised and released over 120 small-spotted catsharks out of 150 viable egg cases, which were primarily collected directly by local fishermen. They operate under the umbrella of Associació Lamna, the small NGO they cofounded in the seaside town of Valencia, Spain, to promote shark conservation and research.

Biologists Rescue Unborn Baby Sharks at Fish Markets

Divers from Oceanogràfic València and Associació Lamna release a juvenile small-spotted catshark that was raised in captivity.

Vicent Renovell

Lamna is their answer to a sense of apathy they discovered as PhD candidates: the biologists had found that few people around them—including some in the marine sciences field—cared much about sharks. For example, Penadés Suay says, Spain has a national program to respond to stranded cetaceans and sea turtles, but did nothing for stranded sharks until Lamna came along.

“They still only care on paper about cetaceans and marine turtles—we haven’t changed the law,” Penadés Suay says. However, when a shark or ray shows up stranded, the local government now calls Lamna to investigate its cause of death with a necropsy. “We’ve been doing this assistance to stranding scenes since 2012, but by creating this NGO the local government had to recognize our work and to acknowledge this problem,” he adds.

It’s a seemingly contrary attitude to anyone following the status of these animals. Though historical research suggests that sharks, rays, and skates (collectively known as elasmobranchs) were once abundant in the Mediterranean, the swarms of dogfish and hordes of other hungry sharks depicted by ancient art do not survive today. In 2008, researchers estimated that large shark populations in the Mediterranean had declined by more than 97 percent over the last 200 years.

Among skates and rays, grouped together (along with the illustratively named guitarfish) by their winged shape as “batoids,” the problem is even more nebulous. Though some catch records suggest these flatfishes are declining, for many species, there is almost no information available. This is largely because many rays and skates have no commercial value, explains Chrysoula Gubili, a researcher with the Fisheries Research Institute in Kavala, Greece. Gubili is investigating Mediterranean batoid populations and seeking to identify the species sold in Greek markets.

Biologists Rescue Unborn Baby Sharks at Fish Markets

Elasmobranchs—sharks, skates and rays—that have been skinned or filleted are hard to identify once they reach the fish market. This, and the fact that these fishes are often grouped together in unspecific categories in catch records, makes it difficult for researchers to accurately track population data.

Andrew Aitchison/Getty Images

Rays and skates that end up in nets are simply clumped together in fishing logs, Gubili says. When they can’t be sold, often they are not recorded at all.

“Ninety-nine percent of this by-catch is thrown away, so we don’t even have valid numbers of the actual catches, which fishermen don’t report,” says Gubili. “So this is the mess we’re trying to deal with.”

Into this mess, some biologists have started bringing babies. Nowell was the first: in late 2011, in Sharklab-Malta’s earlier days, he was conducting a survey of the different shark species sold at the Valletta market when something caught his eye. It was an egg case, poking out of the cloaca of a whole shark for sale.

On a whim, he took the egg case home. For two months he watched, with surprise, as it matured within the walls of his home aquarium. When he shone a light through the hazy walls of the egg case, Nowell could see a wriggling, pulsing embryo beginning to grow.

“That was when the thoughts started,” Nowell says. He wondered, Would it be possible to find more babies and raise them to be released? “Prior to this, during the [market’s] cleaning process, anything that couldn’t be sold would just be thrown away. Our opportunity is giving a chance to something that would simply be discarded.”

That first shark Nowell brought home from the market never made it out of its egg case; Nowell would later learn that the water temperature in his aquarium was too high for it to survive. But since then, Sharklab-Malta has successfully raised and released 316 sharks into the wild, working with both small-spotted catsharks and their larger relative, the nursehound. In 2018, he coauthored the first paper outlining how to recover shark babies from dead mothers.

In 2016, Sharklab-Malta became a member of the European Elasmobranch Association (EEA). That year, Nowell presented a poster of Sharklab’s egg-case project at one of the EEA’s meetings. It caught the attention of others in the shark world, including a young Spanish graduate student looking for a thesis topic: Pablo García Salinas. “I tried to connect the dots and say, Perhaps I can do that,” García Salinas says.

Unlike in Malta, Valencia’s fish market doesn’t offer whole sharks for sale to scour for egg cases; by the time they make it to the market, sharks are nothing but a piece of white fish, or a swordfish look-alike. (This, too, could add to the apathy Spanish consumers feel for sharks, García Salinas theorizes; in a market, these animals are not labeled with the Spanish word for shark, tiburón, but instead with titles like cazón, a word commonly used for several types of fish.)

García Salinas started developing relationships with local fishermen, who agreed to let him sort through the day’s catch before bringing it to market. The fishermen also agreed to collect egg cases that snagged on their nets as they dragged on the bottom, storing them in water bottles, buckets, and plastic baggies until they got back to shore.

Working off Nowell’s original protocol, García Salinas began raising small-spotted catsharks in Oceanogràfic València, the largest aquarium in Europe. The task wasn’t without obstacles at first.

“We used to joke, just like they once said there are 1,000 ways to die in the west, there are 1,000 ways to die as an egg,” says Penadés Suay, who was a fellow graduate student at the University of Valencia and teamed up with García Salinas both on the project and to found Lamna in 2017. They rattled off baby-shark fatalities they’ve seen in the lab: cooked by high temperatures, picked off by crabs, munched by sea urchins, or even devoured from within by polychaete worms, which enter the egg case and eat the young shark alive.

Yet for Sharklab-Malta and Lamna alike, their successes started to get attention. Local news featured photos and videos of the baby sharks. Facebook posts garnered surprised, adoring comments. Several months after the young sharks hatched, divers from both groups released them in deeper waters, where temperatures were cooler and where the young sharks could hide from predators. Yet even so, kids and adults who learned about the projects started turning up on the beaches and piers to see the young transplants off. García Salinas and Penadés Suay started noticing that fishermen who had helped them collect shark eggs came, too. Sharklab-Malta began notifying followers of their shark releases on Facebook and giving short quayside talks about their work to capitalize on the eager audience.

Biologists Rescue Unborn Baby Sharks at Fish Markets

A fisherman working with biologists at Associacó Lamna prepares to release a small-spotted catshark. Fishermen often supply unhatched shark eggs to the biologists, and are then given the opportunity to later release the sharks.

Vicent Renovell

In 2019 and early 2020, Lamna piloted a program to bring their work to a classroom in a local school. Instead of rearing butterflies or silkworms, as is commonplace in various parts of the world, kids spent several months raising sharks. The reaction from children has been the most remarkable, the scientists say.

“They’re always really curious—and they are not afraid,” says García Salinas; fear of sharks always seems to come from the adults around them. With their tiny mouths and mostly bottom-feeding diet, small-spotted catsharks themselves pose no danger to humans. Yet by introducing kids to sharks early, García Salinas hopes to rewrite the classic fearful narrative for all sharks: “If they start taking care of these animals when they are young, perhaps when they grow up they will start other projects that make something change.”

Lamna’s school shark project had to be cut short after its first year, thanks to the COVID-19 pandemic. But García Salinas and Penadés Suay are hopeful that their model will continue not only in Spain, but elsewhere around the world. It can easily be exported: all a teacher needs is a small refrigerator, a tank, an oxygen bubbler, and a little bit of know-how to make salt water and maintain the tank pH, and there could be a baby shark in every classroom.

Ultimately, the teams at Sharklab-Malta and Lamna say that this educational side to their work is likely where they anticipate having the biggest impact. Even if the sharks they raise never manage to make a dent in the population, the researchers involved all hope that the public—adults and kids alike—see the ocean and its creatures anew, through the eyes of its babies.

“It’s about creating a connection, not just with sharks, but with the sea,” Penadés Suay adds. “Not seeing the sea as a public swimming pool, but as a habitat.”

It’s no small task to keep a cohort of baby sharks alive day after day. Even on a good day, when there are no flesh-eating worms devouring them inside out, the young sharks need feeding once or twice a day. They’re highly temperature sensitive and so require constant monitoring for temperature changes. Electrical blackouts and equipment failure can quickly become fatal. Researchers working on the egg-case project have described the time commitment as not unlike raising a small human child.

But is such an investment worth it if something eats the babies not long after they’re released? Shark expert Nick Dulvy has his doubts.

“It’s so, so hard, because you don’t want to be seen punching down at people just doing their best,” says Dulvy, a professor of marine biodiversity and conservation at Simon Fraser University in British Columbia, and leader of the IUCN’s Global Shark Trends Project. “But when people say they’re rearing baby skates or baby sharks and putting them into the ocean, they’re just feeding wild fish.”

Dulvy explains that for sharks and skates, like most fish species, any one individual contributes little to the growth of a population as a whole. Throughout a shark’s life, it will produce hundreds of eggs; rather than investing energy in an individual egg, every egg is a bit like a lottery ticket, with a slim chance of cashing out as an adult shark.

The value, therefore, is not in each baby shark; it’s in the adult that’s capable of making them. And because many sharks can take years—some species up to four decades—before they are able to start reproducing, Dulvy suggests that the greatest impact for a population would come from measures that protect reproductive-age adults, like science-based catch limits.

“The right question to ask is, given that there are few adults in the population, what’s the best conservation activity I should be taking? Should I be focusing my efforts on reducing mortality on adults or rehabilitating juveniles?” Dulvy says, adding: “Your effort is always better spent focusing on the subadults and adults.”

Yet even Dulvy concedes that there are situations where such an investment might make sense. He, and other shark researchers, highlighted the international effort to restore the wild population of zebra sharks, an endangered species native to the Indo-Pacific. Rather than collecting them from the wild, egg cases for the Stegostoma tigrinum Augmentation and Recovery (StAR) project will come from adults bred in zoos and aquariums around the world. The boldly striped-and-spotted sharks are a popular attraction in such institutions, many of which have their own zebra-shark breeding programs—which have been so successful that the species may soon be more populous in captivity than it is in the wild.

The key to the StAR project’s success lies in the egg cases themselves: they are remarkably hardy and much more likely to tolerate being flown back to their native range than an animal would once hatched.

Biologists Rescue Unborn Baby Sharks at Fish Markets

Biologists use a light to “candle” a shark egg case, as a way to observe the development and health of the embryo.

Courtesy of Asociación Cayume

Starting in early 2022, participating organizations plan to ship these egg cases by air to Indonesia. They’ll hatch there in specially designed tanks, but will then be transferred to a specialized pen located on a wild reef, minimizing predation while allowing the young sharks to forage naturally for shellfish and small fish as they grow. Once they’re more than half a meter long—too large to be an easy snack—the young sharks will be released into a marine protected area. There, researchers hope, they should be safe from the fishing that previously decimated the population.

According to biologists on the egg-case projects, there is one group that might be worth this sort of meticulous, long-term planning to rehabilitate to adulthood: skates. Unlike rays, which only give birth to live young, all skate species take the hands-off (or rather, “fins-off”) approach of laying egg cases. This makes them good candidates for egg-case restoration—as does their unlucky superlative as one of the most endangered groups of elasmobranchs.

Even as fishermen take batoids both as by-catch and in targeted fisheries, the lack of knowledge about them, combined with a lack of public interest in their conservation, has led to particularly dire straits for these flatfish. Of the elasmobranchs that the IUCN ranks as threatened—those in the categories of vulnerable, endangered, and critically endangered—41 percent are batoids. More than 12 percent of batoids are considered data deficient, making it difficult to gauge their vulnerability.

On the Spanish island of Mallorca, the third group of researchers on the “egg-case case” have specialized in raising these highly vulnerable elasmobranchs, and maybe, one day, rehabilitating their kind. That is, if they can keep them alive.

After a week of storms, it was a perfectly calm, azure-blue Mediterranean day. Yet for Clàudia Pich Esteve and Emmanuella Orero Rubio, everything seemed to be going sideways.

After a morning spent measuring baby sharks, gathering data for their imminent release, the two researchers with Mallorca’s Asociación Cayume were headed out to sea with their team. Then suddenly, just minutes from the coast of Port d’Andratx, the motor on their boat died.

With two plastic containers of baby small-spotted catsharks sloshing in the front of the boat, the team started rowing back toward shore, their panic rising. They had already subjected the babies to a lot of stress for the day; if they abandoned the trip now to fix the boat, they would have to repeat the process and stress them even further.

This was especially worrisome for the third container in the boat’s bow, and the precious cargo within. Inside was a fluttering circle of skin, small enough to fit on the palm of your hand, with two bold eye-like spots: a five-month-old male brown skate. It was also the only surviving member of a pair they were supposed to release that day.

Biologists Rescue Unborn Baby Sharks at Fish Markets

Two brown skates, also called brown rays, await release.

Courtesy of Asociación Cayume

That skate represented the culmination of almost exactly a year of work for the Cayume team. Though Cayume was founded in 2015, the organization kicked off its first scientific research in May 2020 with a one-year pilot project, focused on raising skates from egg cases. The choice to focus on skates was both an attempt to find a niche among the other egg-case projects and a response to the poor status of rays and skates in the Mediterranean and beyond.

A year of raising skates quickly showed that the flat elasmobranchs were trickier to raise than their shark cousins. The egg cases were more delicate, less tolerant of the rough treatment and temperature swings that came with being hauled up in a fishing net. The baby skates grew slowly and proved to be picky eaters. From the 68 egg cases Cayume received from fishermen throughout the year, only 10 skates were born. Eight survived to a releasable size.

A little over four months after hatching, the first six were released into the wild, in November 2020. Five months later, one of the remaining two skates died unexpectedly, just a week before its scheduled release date. (For comparison, 10 of the 13 small-spotted catsharks Cayume received in egg cases from a market survived to release.)

It was a whirlwind year, one that Orero Rubio describes as “over our heads at some points.” All of Cayume’s members have full-time jobs, and tending the baby skates took up much of their remaining free time. In addition to regular tank cleaning and daily feeding, the two might find themselves called away at the end of a long day to pick up new eggs. Power outages twice sent their team scrambling to relocate the babies before their tanks became fatally hot. On one of these occasions, that rescue mission included wading through ankle-high water after waves from a powerful storm jumped the sea wall and broke down their lab’s door.

Yet at the end of it, the two marine biologists found themselves even more motivated to work on skates’ behalf.

“We think it’s a good thing we are working with skates, because they are less known to the general public,” says Pich Esteve. Even with the public’s historical fear of sharks, there’s a growing awareness of their simultaneous importance and vulnerability—yet no such awareness exists for other elasmobranchs. To Orero Rubio, her work offers a potential solution. “For whatever reasons, skates haven’t been given so much importance. But when you see them in the wild, the rays and skates are beautiful. I’ve dived with sharks, rays, mantas, and me, I prefer the skates and rays.”

The Cayume team’s biggest priorities are to recruit more fishermen to participate in their project and increase the number of skates and sharks they release. But should the funding come through to continue their project, the Cayume team is also hoping to focus future efforts on more vulnerable skate species in the Mediterranean, whose populations might be bolstered by husbandry efforts. In recent conversations with a fisheries department official, they identified a potential target: the white skate, classified as endangered by the IUCN. These massive skates, which grow to more than two meters long, have been increasingly caught as by-catch around the nearby island of Formentera.

Back at the Port d’Andratx release day, the team examined their options. It might take hours or days to fix the boat or find another. With their babies quickly warming in the Mallorca sunshine, they made a quick decision: to head to a nearby beach where they could dive from shore but still get to the deep, cool water and seagrass meadows needed to keep young animals safe.

They descended slowly, plastic containers in hand. The young skate appeared almost frozen, flattened against the bottom of the container. Yet when the lid came off and Pich Esteve tipped the container forward, it fluttered out with something like curiosity.

Biologists Rescue Unborn Baby Sharks at Fish Markets

Divers from Asociación Cayume release a skate into the wild after it was raised in captivity.

Courtesy of Asociación Cayume

They watched the skate approach a rock, so different from the plastic seagrass of its lab habitat, and slowly figure out it had to swim over it. “It was really beautiful,” Orero Rubio says. At the time, she remembers Pich Esteve commenting that “it was like seeing a small kid discovering life.”

Pich Esteve and Orero Rubio—and indeed, all of the scientists on the egg-case projects—frequently reference moments like this. It comes up most often when talking about how difficult it can be to work on a project with such a high rate of failure. They know the reality of the animal world, and how unlikely it is that the babies they release will change their population numbers. Yet they couldn’t help but find something beautiful in their work—a sense of undoing, in some small way, the harm that their own species has done.

Despite his skepticism about the egg-case projects, Dulvy noted that he didn’t want to deride this angle of the work.

“It’s really churlish to pour scorn on hopeful activities,” he says. “With climate change, overfishing, everything—everybody’s looking for a little thing they can do.”

Indeed, for many, that’s what it appears these babies are: a symbol of hope. Which, in itself, is not that surprising. No matter their species, that’s what babies have always been.

This article is from Hakai Magazine, an online publication about science and society in coastal ecosystems. Read more stories like this at

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