Return of Jaws: The morality of selective shark culling

When a shark bit or killed a swimmer, people within the past century might take out hundreds of the marine predators to quell the panic, like executing everyone in a police line-up in order to ensure justice was dispensed on the guilty party.

Eric Clua, a professor of marine biology at the École Pratique des Hautes Études in Paris, said the rationale behind shark culls in the past was simple: fewer sharks, fewer attacks. That reasoning also drives methods such as shark nets and baited hooks, which are currently in use at a number of Australian and South African beaches that are frequently visited by sharks. Nature, he notes, pays too great a price. “They are killing sharks that are guilty of nothing,” said Dr. Clua, who studies the ocean predators up close in the South Pacific.

Dr. Clua said he has found a way to make precision strikes on sharks that have attacked people through a form of DNA profiling he calls “biteprinting.” He believes it’s usually just solo “problem sharks” that attack humans repeatedly, analogizing them to terrestrial predators that have been documented behaving the same way. Instead of culling every bear, tiger or lion when only one has serially attacked people, wildlife managers on land usually focus their ire on the culprit. Dr. Clua said that problem sharks could be dispatched the same way.

This summer, Dr. Clua and several colleagues published their latest paper on collecting DNA from the biteprints of large numbers of sharks. Once a database is built, DNA could be collected from the wounds of people who were bitten by sharks, and matched to a known shark. The offending fish would then need to be found and killed. Critics have taken issue with every facet of this plan. “That’s not how fishing works,” said Catherine Macdonald, a lecturer in marine conservation biology at the University of Miami. “Even when you have a satellite-tagged shark and you know where it is, if you turned up at the site and put a hook in the water, there’s no reason to think you would definitely catch that shark.”

The theory of the “problem shark” has its origins in a series of attacks in New Jersey in 1916 that killed four people, shocking Americans at the time. Fishermen captured and killed many sharks in the aftermath, and newspaper accounts said that one, a great white, may have had human remains in its stomach.

However people react when shark attacks do occur. According to the International Shark Attack File at the University of Florida, there were 64 unprovoked attacks on humans last year and 41 provoked attacks, meaning a person “initiates interaction with a shark in some way.” Five attacks were fatal. More people are killed by falling trees in the U.S. every year.

While shark attacks are uncommon, so are shark culls, although a prominent surfer recently called for one on Réunion Island in the Indian Ocean, which is home to bull sharks. Instead, a number of countries deploy shark nets, similar to fences, beyond the surf at popular beaches. Dangerous sharks get tangled in the nets, but so do harmless ones, along with dolphins, sea turtles and other marine life. In place of these methods, many beach authorities have embraced more humane methods of prevention over extermination. Drones, blimps and tags connect to apps that warn lifeguards and bathers to steer clear of beaches when sharks are around. And after two fatal attacks occurred in New England in recent years, Cape Cod residents received tourniquet training.

Jason Nark is a journalist with NYT©2020