According to new research, nearly two-thirds of the sharks and rays that live around the world’s coral reefs are threatened with extinction with potentially dire side effects for ecosystems and coastal communities.
Overfishing was the main cause of declines over the past half century, with the largest sharks and rays particularly affected.
“These sharks and rays have evolved over 450 million years and survived six mass extinctions, but they can’t cope with this fishing pressure,” said Professor Colin Simpfendorfer, a world expert on sharks and rays and one of the study’s lead authors. by James Cook of Australia. University.
“This is not just a few species,” he said. “This is a broad extinction crisis.”
As sharks and rays disappear, the study said there would be cascading effects on other species with “increasing ecological consequences for coral reefs, many of which will be difficult or impossible to reverse,” wrote a team of more than 30 researchers.
As global warming threatens the future of coral reefs around the world, the pressures facing shark populations will only worsen, the authors said.
Without urgent and large-scale global action to reduce the number of sharks and rays being caught, there would be “increasingly dire consequences for the health of the coral reef ecosystem and the coastal communities that depend on them.”
Tea new study, in the journal Nature Communicationsit is based on the findings of a 2020 study that concluded that sharks were “functionally extinct” in 20% of the world’s coral reefs.
The authors of the new study examined assessments of the conservation status of all 1,200 species of sharks and rays. coordinated in 2021 by the International Union for Conservation of Nature. Coral reefs are inhabited or used by 134 of these species.
Using a variety of previous studies and fishing data, the authors said that reef sharks and rays were much more at risk than other sharks and rays.
Larger species that travel long distances were more vulnerable because they were traveling through different jurisdictions that had different levels of protection.
Among the 134 species, only one, the bluespotted ribbontail ray, was known to be increasing globally.
Lead author Dr Samantha Sherman, from Simon Fraser University in Canada, said larger species such as bull, tiger and hammerhead sharks and manta rays were at higher risk because they tended to be more easily caught in nets.
“But also, they don’t mature until they’re around 20 years old, so when they’re fished, it takes a long time for the population to build up,” he said. “When they are caught before they can reproduce, we see these drastic declines.”
Fourteen of the 134 species reviewed were already critically endangered; nine of which were rays. “The future doesn’t look very bright unless we act now,” Sherman said. “It has to be a global effort. For example, bull sharks are found in more than 150 countries, but if they are only protected in a few, that has an extreme impact on their population.”
Simpfendorfer said that while climate change was degrading reef habitats, fishing was a much more immediate threat that, if left unchecked, could drive many species to extinction within a decade.
“That will lead to the next mass extinction if we don’t act very soon,” he said.
Professor Jodie Rummer, a marine biologist and shark and ray expert at James Cook University who was not involved in the research, said removing top predators from any ecosystem could have devastating impacts on entire ecosystems.
Preventing the species from being over-exploited, or caught as “bycatch” in nets, was possible, he said, but a challenge across different geopolitical boundaries.
He said that creating marine parks where fish are protected from fishing should also be seen as a bridge to protect them from global warming.
Reef habitats for sharks and rays had already been degraded by global warming, and sharks and rays were forced to move, adapt, or die.
“The homes of reef-associated sharks and rays have seen a rapid succession of massive coral bleaching events, heat waves, and multiple severe tropical cyclones,” Rummer said.
“Putting dotted lines around the waters doesn’t mean those waters won’t warm and those reefs won’t bleach.”