The past 50 years have seen the number of sharks and rays in the world’s oceans drop by more than 70 per cent, a new study has shown.
Researchers from Simon Fraser University in Canada believe almost three-quarters of shark and ray species are headed towards extinction.
Their findings, which have been published in the Nature journal, come after Australia recorded a 90-year high in shark attack fatalities in 2020.
The researchers identified overfishing as the main cause behind the 71 per cent decline in oceanic sharks and rays since 1970.
Using a model based on biodiversity indicators, scientists found the number of sharks and rays caught compared to the total population of these animals has had an 18-fold increase since 1970.
The team analysed 18 shark species and found the oceanic whitetip shark, the scalloped hammerhead and the great hammerhead were critically endangered.
“The global abundance of oceanic sharks and rays has fallen to the point that 75 per cent of these species now qualify as threatened with extinction,” said James Cook University’s Dr Cassandra Rigby.
“The alarming trend is that there has been this decline, and that is even maybe more severe than we think because we only started looking at analysis about 1970.
“These open ocean fishing fleets have been expanding globally since before the 1950s.”
The clear driver of the “alarming” trend was a doubling of fishing pressure and a tripling of shark and ray catches, the team of researchers from universities around the world concluded.
The scientists urged governments worldwide to act fast to prevent the extinction of huge numbers of shark and ray species, for example by introducing upper limits to fishing, so that numbers can be recovered.
Despite poor outlooks for many other species, great white sharks and the great hammerhead shark populations in the Northwest Atlantic Ocean appeared to be recovering due to strict US laws now protecting them.
Similar protections, including science-based fishing limits, are urgently needed across to globe to prevent shark and ray population collapses, Dr Rigby says.
“I hope it is a call to action. We can’t just sit back and do nothing.”
The high number of shark attacks in Australia is not an indicator that populations are thriving, she says.
“We’ve got 1200 species of sharks and rays in the world and those responsible for attacks are just a couple of species.”
Eight Australians were killed in shark attacks in 2020, the highest number since 1929.
The paper, published on Thursday, is part of the Global Shark Trends Project, which is reassessing the population of 1200 species around the world and marks the first global analysis of its kind, the authors say.
-with AAP
