Rising Extinction Risk for Sharks and Rays
New research shows oceanic shark and ray numbers are down by more than 70 per cent over the past 50 years, and James Cook University scientists fear some species are facing extinction.
JCU’s Professor Colin Simpfendorfer and Dr Cassandra Rigby were part of an international team of authors that found dramatic declines after they calculated two biodiversity indicators for oceanic sharks and rays worldwide.
“The numbers show the global abundance of oceanic sharks and rays has fallen to the point that 75% of these species now qualify as threatened with extinction,” said Dr Rigby.
She said the scientists considered a number of reasons for the decline, but the clear driver was a doubling of fishing pressure and a tripling of shark and ray catches.
“This amounts to an 18-fold increase in Relative Fishing Pressure - exploitation relative to the number of fish left. The decline may be even more severe, as these analyses start in 1970 while fishing fleets have been expanding globally since before the 1950s,” said Dr Rigby.
Professor Simpfendorfer said despite the bad news, Great White Sharks and the Great Hammerhead Shark populations in the Northwest Atlantic appear to be recovering due to strict US laws now protecting them.
“Fishing limits are needed immediately to prevent shark and ray population collapses. Governments should adopt, implement, and enforce - at domestic and regional levels - science-based catch limits and other protective measures,” said Professor Simpfendorfer.
He said scientists were also warning of the consequences of doing nothing.
“There is a moment when depletion of a species reaches a point of no return. If nothing is done and we reach that point then we are gambling on what a future without sharks and rays in our oceans will be like,” said Professor Simpfendorfer.
The paper is a project of the Global Shark Trends Project (GSTP), a collaboration of the IUCN Shark Specialist Group, Simon Fraser University, James Cook University, and the Georgia Aquarium established with support from the Shark Conservation Fund to assess the extinction risk for chondrichthyan fishes (sharks, rays, and chimaeras).
The GSTP team engaged more than a dozen additional experts from around the world to complete the oceanic shark and ray analysis.