The alarm bells are ringing for many species of the Earth, and a new first of its kind study shows that sharks and rays are among the creatures that are slowly disappearing from nature. Populations of the apex predators of the open ocean's food web have declined by more than 70 percent since 1970, according to a new study.
The study was published in the journal Nature.
Half a century of tremendous decline
"The last 50 years have been pretty devastating for global shark populations," says Nathan Pacoureau, a biologist at Simon Fraser University and a co-author of the study. It was long known that individual shark species are declining; however, the new study, which is based on 57 global datasets, shows just how bad the damage was on the shark and ray populations in just half a century.
The researchers, led by biologist Nathan Pacoureau from Simon Fraser University in Canada, examined population data for the world’s 31 oceanic shark and ray species.
It was seen that the abundance of oceanic sharks and rays declined by more than 70 percent between 1970 and 2018 globally. The study says that 24 of the 31 species of sharks and rays are threatened with extinction with oceanic whitetip sharks, scalloped hammerhead sharks, and great hammerhead sharks are being considered critically endangered.
Overfishing taking its toll
This fall was linked primarily to overfishing. Global fishing fleets have doubled since the 1950s, and while sharks are do intentionally caught from time to time, they are often caught accidentally while fishing for other species. Instead of being turned to the water, however, they are kept and sold most of the time.
The reason for this is their ability to sense outside changes quickly from a great distance which enables them to get to where the fishing is happening first. The fishing pressure is especially hard for oceanic shark species since they take several years to reach sexual maturity and have fewer children. "Their populations cannot replenish as quickly as many other kinds of fish," says Pacoureau.
This could have huge implications for nature. "When you remove top predators of the ocean, it impacts every part of the marine food web," says Stuart Pimm, an ecologist at Duke University. "Sharks are like the lions, tigers, and bears of the ocean world, and they help keep the rest of the ecosystem in balance."
The new study, among many others, is a reminder for the international communities to take action to reverse the detrimental effects of human activities while there’s still time.