Shark Populations Dropped 71 Percent Since 1970
2021-02-02
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1Scientists have known for decades that the numbers of some shark species are decreasing.
2But a new study shows just how severely worldwide populations have dropped in the past 50 years.
3The numbers of oceanic sharks and rays fell more than 70 percent worldwide between 1970 and 2018.
4The information comes from a study that appeared recently in the publication Nature.
5Stuart Sandin is a marine biologist who works at the Scripps Institution of Oceanography.
6He says that sharks are great hunters, fast swimmers and have extraordinary senses.
7Sandin adds that they can identify any changes in the ocean from a great distance, such as smells or tiny changes in water flow.
8Their ability to quickly sense anything outside the norm in their environment helps them find food in the open ocean.
9But it also makes them especially at risk in the face of increased international fishing pressure.
10"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.
11Twenty-four of the 31 species of sharks and rays are threatened with extinction.
12Three species - oceanic whitetip sharks, scalloped hammerhead sharks and great hammerhead sharks - are considered critically endangered.
13Nathan Pacoureau is a biologist at Simon Fraser University in Canada and one of the writers of the study.
14He said, "The last 50 years have been pretty devastating for global shark populations."
15Sometimes sharks are caught on purpose by fishing boats.
16But more often they are caught while fishing for other species such as tuna and swordfish.
17Sharks and rays are both fish with skeletons made of cartilage, not bone.
18Unlike most other kinds of fish, they are not able to reproduce for several years, and also produce fewer young.
19Pacoureau said sharks reproduce more like mammals than fish, so "their populations cannot replenish as quickly as many other kinds of fish."
20The number of fishing boats in the open ocean has risen sharply since the 1950s.
21Climate change and pollution also place shark survival at risk.
22But increased fishing pressure is the greatest threat for every oceanic shark species.
23Stuart Pimm is an ecologist at Duke University and was not involved in the study.
24He said the removal of top hunters like sharks from the ocean affects all sea life.
25"Sharks are like the lions, tigers and bears of the ocean world, and they help keep the rest of the ecosystem in balance," Pimm said.
26I'm Jonathan Evans.
1Scientists have known for decades that the numbers of some shark species are decreasing. But a new study shows just how severely worldwide populations have dropped in the past 50 years. 2The numbers of oceanic sharks and rays fell more than 70 percent worldwide between 1970 and 2018. The information comes from a study that appeared recently in the publication Nature. 3Stuart Sandin is a marine biologist who works at the Scripps Institution of Oceanography. He says that sharks are great hunters, fast swimmers and have extraordinary senses. 4Sandin adds that they can identify any changes in the ocean from a great distance, such as smells or tiny changes in water flow. 5Their ability to quickly sense anything outside the norm in their environment helps them find food in the open ocean. But it also makes them especially at risk in the face of increased international fishing pressure. 6"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. 7Twenty-four of the 31 species of sharks and rays are threatened with extinction. Three species - oceanic whitetip sharks, scalloped hammerhead sharks and great hammerhead sharks - are considered critically endangered. 8Nathan Pacoureau is a biologist at Simon Fraser University in Canada and one of the writers of the study. He said, "The last 50 years have been pretty devastating for global shark populations." 9Sometimes sharks are caught on purpose by fishing boats. But more often they are caught while fishing for other species such as tuna and swordfish. 10Sharks and rays are both fish with skeletons made of cartilage, not bone. Unlike most other kinds of fish, they are not able to reproduce for several years, and also produce fewer young. 11Pacoureau said sharks reproduce more like mammals than fish, so "their populations cannot replenish as quickly as many other kinds of fish." 12The number of fishing boats in the open ocean has risen sharply since the 1950s. Climate change and pollution also place shark survival at risk. But increased fishing pressure is the greatest threat for every oceanic shark species. 13Stuart Pimm is an ecologist at Duke University and was not involved in the study. He said the removal of top hunters like sharks from the ocean affects all sea life. 14"Sharks are like the lions, tigers and bears of the ocean world, and they help keep the rest of the ecosystem in balance," Pimm said. 15I'm Jonathan Evans. 16Christina Larson reported on this story for the Associated Press. Jonathan Evans adapted this story for Learning English. Bryan Lynn was the editor. 17________________________________________________________________ 18Words in This Story 19cartilage - n. a strong but flexible material found in some parts of the body (such as the nose, the outer ear, and some joints) 20devastating - adj. causing great damage or harm 21ecosystem - n. everything that exists in a particular environment 22extinction - n. the state or situation that results when something (such as a plant or animal species) has died out completely 23mammals - n. types of animals that feed milk to its young and that usually have hair or fur covering most of its skin 24primary - adj. most important 25replenish - v. to fill or build up (something) again 26species - n. a group of animals or plants that are similar and can produce young animals or plants; a group of related animals or plants that is smaller than a genus