انخفاض أعداد أسماك القرش
January 27, 2021 - Global numbers of oceanic sharks and rays have fallen by 71% in the last 50 years, due primarily to overfishing. A new study calls on governments to act immediately to prevent a collapse in populations.
Biologist Nathan Pacoureau and colleagues estimated the relative abundance of 18 oceanic species of sharks and rays from 1970 to 2018 and assessed the risk of extinction for all 31 oceanic shark and ray species.
The authors found that, globally, the abundance of oceanic sharks and rays declined by 71.1% from 1970 to 2018.
Three formerly abundant species – the Oceanic whitecap shark, the Scalloped hammerhead, and the Great hammerhead – are now classified as critically endangered, the highest threatened category in a list that is produced by the International Union for Conservation of Nature (IUCN).
And four are endangered – the Pelagic thresher, Dusky shark, the Shortfin mako and the Longfin mako.
In total, more than three-quarters of shark species are now threatened with extinction.
There are some encouraging findings. The white shark is now recovering in several regions, aided by retention bans. Hammerhead shark populations are rebuilding in the Northwest Atlantic, owing to strictly enforced quotas throughout their U.S. range.
The authors argue that immediate action is needed to prevent collapses in populations. Specifically, they call on governments to implement catch limits to help promote species recovery.