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article imageStingray populations in decline

By Tim Sandle     Jan 25, 2014 in Environment
A new report finds that about a quarter of the world’s cartilaginous fish species are at risk of extinction. This includes many rays and some shark species.
In what has been heralded as the first major international survey of its kind, a global team of marine biologists have issues a warning about the decline of many types of cartilaginous fish. Cartilaginous fish (or chondrichthyes) are fish that have a skeleton made of cartilage, rather than bone. As the fish do not have bone marrow, red blood cells are produced in the spleen.
All sharks, skates, and rays (e.g., the southern stingray) are cartilaginous fish. The majority of them are marine, though a few do venture into brackish and freshwater. There are two subclasses: the subclass Elasmobranchii (sharks and rays) and the subclass Holocephali (chimaeras).
As a stark warning, the researchers have recently found that of the 1,041 species of cartilaginous fishes (chondrichthyans) investigated, 25 species are critically endangered, 43 are endangered, 113 are vulnerable, and 132 species are “near threatened," according to a report in the journal eLife. The report is called "Extinction risk and conservation of the world’s sharks and rays."
Commenting on the decline, the lead author, Nicholas Dulvy, a marine ecologist at Simon Fraser University in Burnaby, Canada, has said in a statement: "Our analysis shows that sharks and their relatives are facing an alarmingly elevated risk of extinction. In greatest peril are the largest species of rays and sharks, especially those living in shallow water that is accessible to fisheries."
The report, which errs on the side of sharks facing the greatest risk, has been challenged, in part, by the Wildlife Conservation Society. In a report, the society argues that it is in fact rays that face the biggest population declines.
More about Sharks, Rays, cartilaginous fish, Evolution, Extinction
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