This story at the origin appears in The Guardian and is part of Climate Office collaboration.

A third of shark and ray species have been overexploited to extinction, according to an eight-year scientific study.

“Sharks and rays are the canary in the overfishing coal mine. If I tell you that three quarters of tropical and subtropical coastal species are threatened, imagine a David Attenborough series with 75 percent of its predators extinct. If the sharks are in decline, there is a serious problem with the fishery, ”said lead author Nicholas Dulvy of Simon Fraser University in Canada.

The health of “all ocean ecosystems” and food security are at risk, said Dulvy, former co-chair of the shark specialist group of the United States. International Union for the Conservation of Nature (IUCN).

The number of species of sharks, rays and chimaeras, collectively known as chondrichthyan fish, facing “a global extinction crisis” has more than doubled in less than a decade, according to the article published on September 6 in the newspaper Current biology.

Rays are the most threatened, with 41 percent of the 611 species studied at risk; 36 percent of the 536 shark species are at risk; and 9 percent of the 52 species of chimaeras.

Dulvy said: “Our study reveals an increasingly grim reality, these species are now one of the most endangered lineages of vertebrates, just behind amphibians in terms of the risks they face.”

“The widespread depletion of these fish, especially sharks and rays, threatens the health of entire ocean ecosystems and the food security of many countries around the world,” he said.

The assessment is the second to be carried out since 2014, and it comes after a study in January that found shark and ray populations have collapsed by more than 70% in the past 50 years, with previously widespread species such as the endangered hammerhead sharks.

Sharks, rays and chimaeras are vulnerable to overfishing because they grow slowly and produce few young. He was valued that 100 million sharks are killed by humans each year, overwhelming their slow reproductive capacity. Industrial fishing was a “key threat” to chondrichthyans, either alone or in combination with other fisheries, the authors said.

Most sharks and rays are caught “unintentionally”, but they can be the “unofficial target” in many fisheries, according to the report, and are kept for food and feed. Habitat loss and degradation, the climate crisis and pollution are worsening overfishing, the authors said.

The species are disproportionately threatened in tropical and subtropical waters, especially off countries such as Indonesia and India, experts have found, due to very high demand from large coastal populations combined with fisheries. mostly unregulated, often driven by demand for higher value products such as fins.

According to the report, the Chondrichthyans have survived at least five mass extinctions in their 420-million-year history. But, at least three species are now critically endangered and possibly extinct. The Java stingaree has not been recorded since 1868, the torpedo ray from the Red Sea since 1898, and the lost shark from the South China Sea has not been seen since 1934. Their disappearance would be the first time in the world that marine species are becoming extinct due to overfishing.

Colin Simpfendorfer, assistant professor at James Cook University in Queensland, Australia, said: “The tropics are home to an incredible diversity of sharks and rays, but too many of these inherently vulnerable species have been heavily fished for more than a year. century by a wide range of fisheries. which remain poorly managed, despite countless improvement commitments.

“As a result, we fear that we will soon confirm that one or more of these species has been doomed to extinction due to overfishing, a deeply troubling first for marine fish,” he said. “We will work to make this study a turning point in efforts to prevent irreversible loss and ensure long-term sustainability. “

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