Shark populations are sinking worldwide
In just the past half-century, humans have caused a staggering worldwide drop in the number of sharks and rays that swim the open oceans, scientists have found in the first global assessment of its kind, published Wednesday in the journal Nature.
Oceanic sharks and rays have declined by 71 percent since 1970, mainly because of overfishing.
The collapse probably is even more stark, the authors note, because of incomplete data from some of the worst-hit regions and because fishing fleets already were expanding in the decades before they started their analysis.
“There is a very small window to save these iconic creatures,” said Nathan Pacoureau, a marine biologist at Simon Fraser University in Canada and the study’s lead author.
More than three-quarters of oceanic shark and ray species now are threatened with extinction, jeopardizing marine ecosystems and the food security of people in many nations.
The research offers the latest data point in what is a dismal trajectory for Earth’s biodiversity.
From butterflies to elephants, wildlife populations have plunged in recent decades and as many as 1 million species of animals and plants are at risk of extinction.
But scientists emphasize that conservation works when done correctly, and the study urges governments to adopt measures such as setting science-based limits on how many sharks and rays fishermen can catch and keep.
“Action is needed immediately,” the authors wrote.
Sharks and rays are taken for their meat, fins, gill plates and liver oil. They also often are caught incidentally by fishermen using nets or long lines with thousands of baited hooks to attract tuna or swordfish. Such incidental catch isn’t the main goal, but often it’s welcome when it happens.
That’s one reason sharks are especially vulnerable, scientists say.
But high levels of incidental catch aren’t inevitable, said Sonja Fordham, an author of the study and the president of Shark Advocates International, a nonprofit group dedicated to shark conservation.
“We have volumes of scientific studies now about how you might avoid catching sharks to begin with, and certainly a lot about the best practices for releasing the shark safely and making sure it survives,” Fordham said.