Shark and ray populations have decline by more than 50 percent since 1970 off the back of global overfishing.
A new study, led by Simon Fraser University, said the risk of extinction for many of these species had increased by 19 percent.
Chondrichthyans, which include sharks and rays, are an ecologically diverse group of more than 1199 fish that are increasingly threatened by human activities.
“Overexploitation by target fisheries and incidental capture (bycatch), compounded by habitat degradation, climate change and pollution, has resulted in over one-third of chondrichthyans facing extinction,” the study report says.
“The study also highlights that the overfishing of the largest species in nearshore and pelagic habitats could eliminate up to 22 per cent of ecological functions.”
The study, published in the journal Science, says populations of chondrichthyan fish – sharks, rays, and chimaeras – had declined by more than 50 percent since 1970.
“(Shark and ray) declines first occurred in rivers, estuaries, and nearshore coastal waters before spreading across the oceans and then down into the deep sea”, Professor Nicholas K. Dulvy, of Simon Fraser University,said.
“The sequential depletion of the largest and most functionally important species – such as sawfishes and rhino rays – was followed by the decline of large stingrays, eagle rays, angel sharks, hammerheads and requiem sharks.
“Eventually, fisheries turned to deepwater sharks and skates for the liver oil and meat trade”.
European Institute for Marine Studies researcher Nathan Pacoureau said sharks and rays were important predators and vital for the transfer of nutrients from deeper waters to coral reefs.
Rays were also important for the mixing of and oxygenate sediments which influenced marine productivity and carbon storage.
The paper can be accessed here here.
