Leopard Shark (Triakis semifasciata). Photo by Rhett Butler.
Analyzing the DNA sequences of 4,383 specimens of sharks and rays, researchers have discovered 79 potentially new species, raising both the known diversity of this predacious family and concerns that many species are likely more imperiled than thought. Already 32 percent of open ocean sharks and rays are considered threatened with extinction by the IUCN Red List, due largely to overfishing, finning, bycatch, and prey depletion.
Many of the potentially new species are ‘cryptic’ species, according to the study published in Nature. In other words two species look so similar that scientists have long mistaken them for a single species until the DNA reveals they are not so closely related. This means that some endangered species may be even more threatened when split into two, even smaller, populations.
The scientists were especially surprised by their findings since they only sequenced about half of the world’s 1,200 ray and shark species.
“This will have an impact on what is considered endangered and the fragility of different organisms,” lead author Gavin Naylor with the College of Charleston in South Carolina, told the Scientific American. “These are sentinel species of all sorts of other organisms in the sea which are probably undergoing similar or worse kinds of impacts.”
Experts have begun to warn that the world’s marine ecosystems may suffer a mass extinction. An expert panel last year released a report that argued that the combined impacts of overfishing, pollution, and climate change in the world’s oceans could lead to a widespread collapse in marine life. To deal with these problems the experts recommended immediately slashing carbon emissions, restructuring fisheries towards sustainability, and dealing with sources of pollution, such as plastic and nitrogen run-off.
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