Empty seas: Oceanic shark populations dropped 71% since 1970

This undated photo provided by Dr. Greg Skomal in January 2021 shows a shortfin mako shark. In a study published on Wednesday, Jan. 27, 2021, researchers found the abundance of oceanic sharks and rays has dropped more than 70% between 1970 and 2018. (Greg Skomal via AP) (Greg Skomal)

WASHINGTON – When marine biologist Stuart Sandin talks about sharks, it sounds like he’s describing Jedis of the ocean. “They are terrific predators, fast swimmers and they have amazing senses — they can detect any disturbance in the ocean from great distance,” such as smells or tiny changes in water currents.

Their ability to quickly sense anything outside the norm in their environment helps them find prey in the vastness of the open ocean. But it also makes them especially vulnerable in the face of increased international fishing pressure, as global fishing fleets have doubled since 1950.

“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 Sandin, who works at the Scripps Institution of Oceanography.

Scientists have known for decades that individual shark species are declining, but a new study drawing on 57 global datasets underscores just how dramatically worldwide populations have collapsed in the past half century.

Globally, the abundance of oceanic sharks and rays dropped more than 70% between 1970 and 2018, according to a study published Wednesday in the journal Nature.

And 24 of the 31 species of sharks and rays are threatened with extinction, while three species — oceanic whitetip sharks, scalloped hammerhead sharks and great hammerhead sharks — are considered critically endangered.

“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.

Sometimes sharks are intentionally caught by fishing fleets, but more often they are reeled in incidentally as “ bycatch," in the course of fishing for other species such as tuna and swordfish.