Shark numbers in 'alarming' worldwide decline as many species face extinction, study says
The predators of the seas are in trouble.
Shark populations in the world's oceans have declined by an "alarming" 71% since 1970, according to a study published Wednesday in the British journal Nature.
“The last 50 years have been pretty devastating for global shark populations,” said Nathan Pacoureau, a biologist at Simon Fraser University in Canada and a co-author of the study.
"We document an alarming, ongoing, worldwide decline in oceanic shark populations across the world’s largest ecosystem over the past half-century, resulting in an unprecedented increase in the risk of extinction of these species," the authors wrote.
The research looked at rays as well as sharks: Of the 31 oceanic species of sharks and rays analyzed in the study, 24 are threatened with extinction.
Where marine mammals 'live in harmony with people': Dana Point, California, earns distinction as first Whale Heritage Site in US
Three species of shark (the oceanic whitetip, the scalloped hammerhead and the great hammerhead) have declined so sharply that they are classified as critically endangered – the highest threatened category in a list produced by the International Union for Conservation of Nature.
The risk of extinction is primarily caused by overfishing, study authors said. Although sharks are sometimes intentionally caught by fishing fleets, more often they are reeled in incidentally as “bycatch” in the course of fishing for other species such as tuna and swordfish.
“You drop a fishing line in the open ocean, and often it’s sharks that are there first – whether or not they’re the primary target,” said marine biologist Stuart Sandin, who works at the Scripps Institution of Oceanography.
More: 2020 was an 'unusually deadly year' for shark attacks, with the most deaths since 2013
The number of fishing vessels trolling the open ocean has risen steeply since the 1950s as engine power expanded ships’ range. Although climate change and pollution also imperil shark survival, increased fishing pressure is the greatest threat for every oceanic shark species.
The authors said relative fishing pressure – a measure of the proportion of sharks and rays caught relative to their global population – is 18 times higher than it was 50 years ago. They argued that immediate action is needed to prevent collapses in shark and ray populations. They called on governments to implement catch limits to help promote recovery of the threatened species.
Contributing: The Associated Press
This article originally appeared on USA TODAY: Shark populations are declining worldwide, study reports
