Many Laws to Protect Sharks Have Backfired, Researchers Find

Many of the policies enacted around the world to curb the mass killing of sharks have backfired, partly because well-intentioned rules against taking the predators solely for their fins have led to an increase in demand for shark meat, according to a study published on Thursday.

Sharks have thrived on Earth for more than 400 million years, since before the dinosaurs. But a growing appetite for their fins in some Asian cuisines led to a slaughter that drove several species to the brink of extinction.

The world reacted. Starting in the 1990s, nations drew up rules to stop the practice known as finning, in which fins are removed and carcasses are discarded. Today, 70 percent of countries and jurisdictions have regulations to stop finning or protect sharks.

But the study, which was published in the journal Science, found that many of those policies, which required fishers to land whole sharks, had unwittingly increased demand for their meat and that the expected decrease in shark mortality had failed to materialize. In fact, data shows that shark killing has increased.

“We should have seen a signal in reduced mortality,” said Boris Worm, one of the authors of the study and a professor of marine conservation at Dalhousie University in Halifax, Nova Scotia. “The surprising result is that we didn’t.”

The researchers spent three years calculating global patterns of shark fishing mortality and correlated them with regulations designed to protect the animals. They found that more than 80 million sharks had been killed worldwide by fishing in 2017, from 76 million in 2012.

Almost a third of the sharks killed were threatened species.

The researchers found that countries that enacted narrower regulations to ban finning saw little impact on mortality. These policies also seem to have increased overfishing of coastal species.

A 2021 report from the World Wildlife Fund examined the value of the global trade in sharks and rays. It found that the meat trade was valued at $2.6 billion, surpassing the shark fin market, which was valued at $1.5 billion.

The Thursday study’s findings underscore not only the urgency for countries to develop better strategies to protect sharks, Dr. Worm said, but also the need for continued assessment of the impact of supposedly successful environmental policies.

Asian countries where people traditionally eat shark fins are no longer the main culprits. Spain and Portugal are top exporters, and Brazil is one of the biggest importers.

Brazil was among the first countries in the world to ban finning. But when regulations started to take hold, a market for shark meat, which tends to be inexpensive, also grew as the fish that Brazilians traditionally eat became scarcer in the seas.

“The decline of traditional fishing resources opened the window along with demand for fins,” said Fabio Motta, a marine biologist at the Federal University of São Paulo. “Sharks ended up becoming the next big thing.”

Most Brazilians don’t know they are eating shark meat, according to surveys, largely because shops sell it under a name that most people don’t recognize as an alternate term for shark.

But better management is possible, the study found. Many countries that created shark sanctuaries or enacted other legislation to fully protect sharks were successful in reducing shark mortality. Small island nations like the Bahamas and the Maldives, where people depend on healthy ecosystems for their livelihoods, were clear leaders.

Improving data collection so fisheries can be better monitored and consumers know what they are buying can help, too. Researchers say that banning the retention of endangered and overfished species and banning the use of certain fishing gear can have big impacts.

But drawing up new laws is not enough, said Laurenne Schiller, another author of the study and a postdoctoral researcher at Carleton University in Ottawa. Shark mortality was greater where enforcement capacity was slimmer.

Countries that succeed may find that policies to protect sharks help their economies. A 2017 study by Oceana, an ocean conservation nonprofit, found that shark tourism contributed $221 million to Florida’s economy in the year before, more than 200 times as much as shark finning added to the entire U.S. economy.

The new study also found that shark mortality from fishing beyond coastal waters, where international fisheries run large fleets, had decreased 7 percent. Researchers credit this in part to regulations that banned the trade of certain threatened species.

Still, a third of shark species are endangered today. Their demise would very likely put scores of other ocean species at risk, including those that people around the world depend on for food.

“All ecosystems in the ocean have evolved with sharks in them because they are so ancient,” Dr. Worm said. “When we take sharks out of the ecosystem, we find that the stability of the system is compromised.”

Sharks, Dr. Worm said, are “a canary in the coal mine” for ocean health. “Because they are so sensitive, they can signal when something is wrong,” he added. “We are well advised to listen.”