Sawfish

Extinction Threatens Quarter of Sharks and Rays

A quarter of sharks, rays and chimaeras are threatened with extinction, according to a new study by the International Union for Conservation of Nature. Large, shallow-water species are at most risk.

The group found that only 23 percent of these fish is listed as “least concern” on the IUCN Red List of Threatened Species. Of the 1,041 known species, 25 are listed as critically endangered, 43 are endangered, and 113 are vulnerable to extinction. This is the worst reported status for any major vertebrate group except for amphibians.

“Our analysis shows that sharks and their relatives are facing an alarmingly elevated risk of extinction,” says Dr Nick Dulvy, IUCN Shark Specialist Group Co-Chair and Canada Research Chair at Simon Fraser University in British Columbia. “In greatest peril are the largest species of rays and sharks, especially those living in shallow water that is accessible to fisheries.”

The most threatened families are:

  1. Sawfishes (Pristidae)
  2. Angel sharks (Squatinidae)
  3. Wedgefishes (Rhynchobatidae)
  4. Sleeper rays (Narkidae)
  5. Whiptail stingrays (Dasyatidae)
  6. Guitarfishes (Rhinobatidae)
  7. Thresher sharks (Alopiidae)

Overfishing is the main threat to the species, according to the paper. Reported catches of sharks, rays and chimaeras peaked in 2003 and have been dominated by rays for the last 40 years. Actual catches are likely to be grossly under-reported.

Unintentionally caught sharks and rays account for much of the catch, yet developing markets and depleting fishery targets have made this “bycatch” increasingly welcome. Intentional killing of sharks and rays due to the perceived risk that they pose to people, fishing gear or target species is contributing to the threatened status of at least 12 species.

Sharks and their relatives include some of the latest maturing and slowest reproducing of all vertebrates, exhibiting the longest gestation periods and some of the highest levels of maternal investment in the animal kingdom. This makes them very sensitive to over-fishing.

The Indo-Pacific, particularly the Gulf of Thailand, and the Mediterranean Sea are the two ‘hotspots’ where the depletion of sharks and rays is most dramatic. The Red Sea is also home to a relatively high number of threatened sharks and rays, according to the experts.

The report was published in the journal eLIFE.

Photo credit: Sawfish by Forrest Samuels (CC BY-NC-SA 2.0).

Further Reading:
eLife 2014;3:e00590
IUCN

Jill Studholme

By Jill Studholme. Jill edits SCUBA News (ISSN 1476-8011), the monthly newsletter with articles on diving and marine science.She tweets as @SCUBANews. You can find her on Google+ at https://plus.google.com/+JillStudholme/.

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