- The silky shark, a large, slender species that swims the tropical seas and is listed as vulnerable on the IUCN Red List of Endangered Species, is heavily hunted for its fins and, to a lesser degree, for meat —and is caught in nets as bycatch.
- Between 2020 and 2024, Costa Rica accounted for 82% of global exports of silky shark products, according to a recent report from the United Nations Environment Programme.
- Its exports are under review under CITES, the global wildlife trade treaty: If Costa Rica can’t prove its fishery is sustainable, the CITES Animals Committee will recommend new management measures; without implementation, the country’s export of silky sharks could be suspended.
- Meanwhile, a Costa Rican NGO has questioned the exports’ sustainability and alleged that the silky shark trade is being unduly influenced by the Costa Rican fishing industry.
Inside an inspection facility in Hong Kong in 2018, shark biologist Diego Cardeñosa stared at dozens of large white bags. They were stacked, sometimes six or seven high, beneath strip lights hanging from the ceiling. Each bag weighed more than 50 kilograms (110 pounds) — and was stuffed with shark fins.
“It was the first time I saw that,” Cardeñosa wrote in an email to Mongabay. “Obviously, as a student, it was a shock and [a] reality check for me.”
Cardeñosa, now a shark trade researcher at Florida International University in the U.S., lived in Hong Kong in 2018 and returned repeatedly from 2015 to 2020 as part of his PhD field research at Stony Brook University, also in the U.S.
He helped train law enforcement in Hong Kong to use a mobile DNA kit to identify shark species whose trade is regulated under CITES, a treaty signed by 184 countries and the European Union that establishes rules for international trade in imperiled plants, wildlife, and their products.
Many of the fins Cardeñosa saw in Hong Kong back in 2018 were cut from silky sharks (Carcharhinus falciformis). Like all shark species, silkies are heavily hunted for their fins, which are used in shark fin soup in China and Southeast Asia; they are also netted in vast numbers as bycatch.
Shark numbers have cratered over the last 50 years. A 2024 study found that overfishing has halved populations of roughly 1,200 species of sharks and rays since 1970. An average of 16,500 metric tons of shark-fin products were traded globally each year from 2000 to 2018, with an average yearly value of $323 million, according to a report commissioned by the Federal Agency for Nature Conservation Germany. The fin trade fluctuated over that time, but trended downward overall.
The silky shark, found in tropical waters across the world, is one of the three most traded species in the global shark fin trade, some of which is legal. Much is not.
From 2020-2024, countries exported roughly 6,414 metric tons of silky shark products in direct trade, according to a recent report from the United Nations Environment Programme (UNEP). The majority were shipped out of Costa Rica: roughly 82%. Direct trade refers to the shark products exported by the country where the sharks were caught or landed, under a CITES export permit issued by that country; re-exports are not included.
Between June 2023 and May 2024, Costa Rica exported 734 tons of silky shark meat, worth roughly $1.9 million, and 45 tons of silky shark fins worth about $5 million, according to the Center for Rescue of Endangered Marine Species (CREMA), a Costa Rican NGO. That equates to at least 45,000 sharks killed in one year.
Now, the sustainability of this massive offtake has placed the world’s leading silky shark exporter under scrutiny by CITES.
Exports under fire
The volume of silkies pouring out of Costa Rica sparked a CITES review of this fishery in July. Unless Costa Rica can prove its trade is not impacting silky shark populations, CITES could ban the country from exporting the species.
CREMA has been trying to call public attention to this trade for years, questioning the sustainability of such an intensive harvest and alleging that the country’s trade is unduly influenced by the fishing industry.
“It’s a huge, huge mess, and this mess is because the shark finners are [making] all the calls,” said Randall Arauz, a marine researcher with CREMA and the winner of a Goldman Environmental Prize for his work exposing and campaigning against shark finning. “And all the government entities that are supposed to be counterbalancing this, or controlling it, are all bending over and saying, ‘Yes sir, yes sir, Mr. Shark-finner, whatever you say.’”
The agency in charge, the Costa Rican Institute of Fisheries and Aquaculture (INCOPESCA), did not respond to Mongabay’s request for comment by the time this story was published.
CREMA supports suspension of silky shark exports, with executive director Daniel Arauz-Naranjo telling Mongabay that a ban was “definitely” the best step for their conservation.
“Fishing the sharks — almost any species of sharks — in the way that we’re doing it, it’s going to bring them to extinction eventually,” he said, “because it just takes so long for them to recover.”
The state of silky sharks
Silky sharks are large, slender fish that reach lengths of 2-3 meters (6.6 to nearly 10 feet) and are found across the tropical regions of the Atlantic, Pacific and Indian oceans. Despite their wide range, silkies are listed as vulnerable on the IUCN Red List and declining, according to the most recent assessment, published in 2021.
Global trade is regulated. Silky sharks were listed in 2017 under Appendix II of CITES, which designates wildlife that might become threatened with extinction if trade isn’t carefully controlled and doesn’t harm populations. Countries looking to export these species must obtain permits.
Silky sharks are on Costa Rica’s national endangered species list, Arauz said, which should prohibit them from being commercialized, based on a legal precedent established in a 1999 case regarding sea turtles. In that instance, the country’s Supreme Court ruled that if a species was acknowledged by the state as endangered, it could not be commercialized, Arauz said.
“[Silky sharks are] probably one of the most abundant sharks on Earth,” said Brendan Talwar, a marine biologist at the Scripps Institution of Oceanography at the University of California, San Diego, in the U.S. “But relative to the numbers that once swam around our oceans, it’s a tiny fraction.”
In the Atlantic Ocean, silky sharks are in relatively good shape, he said, but in the Pacific and Indian oceans, they’re being caught in enormous numbers.
“Overfishing is by far the largest threat to any shark or ray out there,” Cardeñosa added.
The vast offtake is a problem for another reason. Silky sharks reproduce far slower than other fish, like tuna and they reach sexual maturity quite late — between 10 and 12 years old. This makes it hard for them to recover from population losses.
Oversight and sustainability in question
In 2017, the Costa Rican government decreed that sharks are commercial species rather than wildlife, Arauz said, transferring their management from the country’s environment ministry to its fishery institute, INCOPESCA. This institute, charged with oversight — providing proof of sustainable fishing, called a “non-detriment finding” — isn’t a government wildlife agency like its counterparts in many other countries. Its stated mission is to manage, regulate, and promote the development of the fisheries and aquaculture sector with an ecosystem approach.
This allows INCOPESCA to use hand-picked scientists and NGOs to establish non-detrimental findings, Arauz said.
That analysis includes precautionary quotas for how many silky sharks should be caught and exported by Costa Rica. Arauz said these quotas aren’t backed by scientific data but are instead based on a percentage of previous landings.
Costa Rica routinely exports more than its quotas, he added.
What’s more, the country is missing roughly 500 tons of silky shark fins, Arauz said, based on a discrepancy between the records of fins landed and those exported. He said he believes these fins were exported illegally.
Another serious issue, Arauz said, is that Costa Rican fishers are catching a disproportionate number of young sharks. It’s a basic principle of fishery biology to allow fish to reproduce at least once before removing them from the population, but he said more than 80% of the silky sharks landed in Costa Rica haven’t yet reached sexual maturity.
“They’re catching more and more sharks per year, and the sharks are getting smaller and smaller,” he said. “You don’t have to be a fishery biologist to predict what’s happening to this population.”
It’s a problem that extends beyond sharks across the world’s oceans. According to a study in the journal Science, “chronic underassessment and undermanagement of fisheries is widespread.”
Under review
The CITES Secretariat confirmed to Mongabay in early August that it would be contacting Costa Rica to officially inform the government of its review and to request documentation of its silky shark trade proving sustainability, specifically requesting “information demonstrating that exports are not detrimental to the survival of the species. Costa Rica will have 60 days to respond.
The CITES Secretariat and the United Nations Environment Programme will also compile a report on silky shark biology, management and trade, including any relevant information provided by Costa Rica. However, the secretariat noted that being selected for review doesn’t necessarily mean a country’s trade is detrimental to the species.
Arauz-Naranjo said he isn’t convinced.
“I think it [will] be really difficult for Costa Rica to prove that they are doing this in a sustainable way,” he said. “We will see what happens.”
The CITES Animals Committee will review the data at its next meeting, in June 2027. If the committee questions sustainability, it will recommend new management measures.
Though these would be recommendations, ignoring them would have consequences. If Costa Rica were not to implement improved management, the CITES Standing Committee could then suspend the country’s silky shark exports.
There is no set time frame for this process, the secretariat told Mongabay, but Arauz-Naranjo said a trade suspension, if it were to come, would be at least two to three years away.
Should CITES eventually levy a ban, the hope is that the country’s fishery could be transformed to focus more on mahi-mahi and tuna, Arauz-Naranjo said. INCOPESCA has funds to do that sort of work, he added, but he said he doesn’t believe the funding will be used properly until the institute undergoes fundamental changes.
INCOPESCA was “basically born out of corruption,” Arauz-Naranjo said. “The whole way that it was created, the whole way that it is structured with a board of directors run by fishermen. Fishermen taking care of the fish — it’s not working.”
INCOPESCA didn’t respond to a request for comment on its authority structure and the allegations of corruption and fishing industry influence within the institute.
An ecosystem unbalanced
Most silky sharks are caught off Costa Rica’s Pacific coast, Arauz-Naranjo said, where a small fleet of semi-industrial longline fishing boats operates, which are owned by several companies, all flying Costa Rican flags. Ostensibly, these fishers are looking for species like mahi-mahi, marlin and swordfish, rather than silky sharks, he said. They usually classify the latter as bycatch — nontarget species caught by their long, branching fishing lines, which can contain hundreds or thousands of baited hooks.
“But if we are exporting 82% of the whole [global market], clearly [silky sharks are] the target of these fishers, even though they say it’s not,” Arauz-Naranjo said.
Careful management is lacking, Arauz said. “If you’re a government officer and you’re working on sustainability, you can’t think such short-term.” The questions an oversight agency should be asking, he argued, are: “Where can we fish? Where shouldn’t we fish? How can we make these populations replenish?”
The Inter-American Tropical Tuna Commission (IATTC), an international body responsible for the sustainable management of various fish species in the Eastern Pacific, requires scientific observers to be present for at least 5% of the fishing effort by a country’s longline fishing boats above a certain size. These observers record catches of targeted fish as well as interactions with nontarget species, like sharks.
A 2026 report by the U.S. National Oceanic and Atmospheric Administration (NOAA), which handles U.S. fisheries, said Costa Rica failed to meet this requirement in 2022, 2023 and 2024.
“Costa Rica argued that it had been unable to implement an onboard observer program due to the small size of its vessels, continuous work schedules, and national regulations regarding working hours,” the report said.
However, the nation has made strides toward implementing an observer program: In June 2025, Costa Rica said it was implementing a pilot program for both human observers and electronic monitoring, according to the report.
Sharks occupy an important role high in the marine food chain, and their loss spells trouble for ocean ecosystems. If silky sharks disappear, other sharks will likely fill their ecological role, Cardeñosa said. But with other species like hammerheads, makos and blue sharks also going down, the environment’s ability to fill these gaps is at risk.
Ecosystems have evolved in synchrony, and sharks are crucial. “Think about the ecosystem as a machine,” Cardeñosa added. “Once you remove certain pieces of the machine, it will not operate the same way, and most likely, will shut down eventually.”
The specter of ecosystem-scale collapse is often brandished to demonstrate why species extinction should matter to people. That argument, Cardeñosa said, is anthropocentric.
“How about … we shouldn’t bring a species to extinction just for the sake of it?” he asked.
Save or let vanish?
Humans disagree on moral and ethical obligations around conservation, and there is evidence that attempts to protect biodiversity aren’t always effective. Recent research published in Nature Communications found that finning regulations had no significant impact on the volume of the overall shark trade. A 2024 study documented a rising trend: “shark kills [rose] to more than 100 million per year [in 2019] — despite anti-finning laws,” it said.
“I think in a perfect world, we find a way to live in balance with other organisms to the best of our ability, while recognizing that we’re going to prioritize ourselves as a species,” said Talwar, the Scripps marine biologist. “I don’t think those have to be mutually exclusive.”
What’s inarguable is that fisheries wield significant power over both wildlife and humans. Capture fisheries brought in 92 million metric tons of aquatic animals in 2024, according to a 2026 report from the Food and Agriculture Organization of the United Nations. Meanwhile, global fish consumption per capita has reached 20.7 kilograms (45.6 pounds) annually, the highest ever recorded, according to the United Nations.
“We’re just at a point in time where, basically, we shape how the Earth looks,” Talwar said. “We shape what species exist — and don’t. We’re literally making decisions about what species we save or let vanish.”
Banner image: Silky sharks like this one, seen in the Bahamas, occupy important roles high in the food chain, and their loss could spell trouble for oceans. Image by Brendan Talwar.
Read more:
Global shark deaths increasing despite finning bans, study shows
The lab-in-a-backpack busting illegal shark fins: Interview with Diego Cardeñosa
Citations:
Dulvy, N. K., Pacoureau, N., Matsushiba, J. H., Yan, H. F., VanderWright, W. J., Rigby, C. L., … Simpfendorfer, C. A. (2024). Ecological erosion and expanding extinction risk of sharks and rays. Science, 386(6726). doi:10.1126/science.adn1477
Burns, E. S., Orofino, S., Wang, K., Bradley, D., D’Costa, N. G., Feitosa, L. M., … McDonald, G. G. (2026). Global trade responses to shark finning regulations. Nature Communications, 17(1). doi:10.1038/s41467-026-75625-1
Worm, B., Orofino, S., Burns, E. S., D’Costa, N. G., Manir Feitosa, L., Palomares, M. L., … Bradley, D. (2024). Global shark fishing mortality still rising despite widespread regulatory change. Science, 383(6679), 225-230. doi:10.1126/science.adf8984
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