The ‘extinction crisis’ of sharks and rays will have a devastating effect on other species

Nearly two-thirds of sharks and rays living on the world’s coral reefs are at risk. And 14 of the 134 species analyzed are critically endangered.

According to new research, nearly two-thirds of sharks and rays living in the world’s coral reefs are threatened with extinction, with potentially dire side effects for coastal ecosystems and communities.

Overfishing has been the main cause of declines over the past half century, with the larger sharks and rays particularly affected.

These sharks and rays have evolved for 450 million years and survived six mass extinctions, but they can’t handle this fishing pressure.said Professor Colin Simpfendorfer, a world expert on sharks and rays and one of the lead authors of the study by James Cook from Australia. University. “That’s not just a few species“, said. “This is a broad extinction crisis”.

sharks and rays, coral reefs, extinction, species, overfishing

Ripple effects of disappearing sharks and rays

As sharks and rays disappear, the study warned that there would be ripple 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 get worse, the authors said.

Without urgent, large-scale global action to reduce the number of sharks and rays caught, there would be “increasingly dire consequences for the health of the coral reef ecosystem and the coastal communities that depend on them”.

Functionally extinct sharks

The new study, published in the journal Nature Communications builds 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 conservation status assessments 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.

Based on previous studies and fisheries data, the authors said that sharks and rays are much more at risk than other sharks and rays.

Larger species that travel longer distances were more vulnerable because they traveled through different jurisdictions with different levels of protection.

The most affected species of sharks and rays

sharks and rays, coral reefs, extinction, species, overfishing
Ribbontail ray with blue spots

Among the 134 species, only one, the blue spotted ray, was increasing globally.

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Lead author Samantha Sherman of Simon Fraser University in Canada said that larger species such as bull sharks, tiger and hammerhead sharks, and manta rays are at greater risk because they tend to be more easily caught in nets.

But also, they don’t mature until they are 20 years old, so when they are fished, it takes a long time for the population to grow.“, said. “When they are captured before they can reproduce, we see these drastic declines.“.

Fourteen of the 134 species analyzed were already critically endangered; nine of which were rays. “The future doesn’t look great unless we act now.said Sherman. “It has to be a global effort. For example, bull sharks are found in over 150 countries, but if they are only protected in a few, it will have an impact on their population.”.

Simpfendorfer said that while climate change is degrading reef habitats, fishing is a much more immediate threat that, if left unchecked, could drive many species to extinction within a decade. “It will lead to the next mass extinction if we don’t act soon.“, said.

The consequences of eliminating predators

Professor Jodie Rummer, a marine biologist and expert on sharks and rays 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.

Prevent the species from being overexploited or captured as “accidental capture” on networks, it was possible, he said, but it was a challenge across different geopolitical borders.

He said that the creation of marine parks where fish are protected from fishing should also be seen as a bridge to protect them from global warming.

The habitats of reefs for sharks and rays they had already been degraded by global warming, and sharks and rays were forced to move and adapt in order not to 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 that those waters won’t warm and those reefs won’t bleach.”.

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