The effect ocean junk is having on sharks and rays revealed

Hundreds of new cases of sharks and rays entangled in nets and plastic waste have been uncovered by researchers using social media.

But they're warning the true number will be much higher, with only a fraction of incidents being seen by human eyes.

"One example in the study is a shortfin mako shark with fishing rope wrapped tightly around it," said Kristian Parton of the Centre for Ecology and Conservation at the University of Exeter.

"The shark had clearly continued growing after becoming entangled, so the rope - which was covered in barnacles - had dug into its skin and damaged its spine."

Study co-author Brendan Godley said with all the other threats marine life faces nowadays, there had been little focus on entanglement.

"We set out to remedy this. Our study was the first to use Twitter to gather such data, and our results from the social media site revealed entanglements of species - and in places - not recorded in the academic papers."

While they recovered academic reports of 557 sharks and rays of 34 different species getting caught up in nets and fishing gear, there were reports of another 559 from 26 different species on Twitter.

The academic and social media reports were consistent in what was to blame - humans.

"Both data sources suggested 'ghost' fishing gear (nets, lines and other equipment lost or abandoned) were by far the most common entangling objects," the researchers said in a statement.

"Other items included strapping bands used in packaging, polythene bags and rubber tyres."

Most at risk were creatures which spend more time near the bottom of the ocean, where junk tends to accumulate; animals which migrate, putting them more at risk of encountering hazards; and those with "unusual" body features, such as sawfish, which make them prone to getting stuck. 

"Although we don't think entanglement is a major threat to the future of sharks and rays, it's important to understand the range of threats facing these species, which are among the most threatened in the oceans," said Parton.

"Additionally, there's a real animal welfare issue because entanglements can cause pain, suffering and even death."

Before you start thinking this is revenge for all the people sharks kill, bear in mind that in 2018, sharks were responsible for only four deaths worldwide. In turn, humans killed about 100 million sharks every year. 

Newshub was able to find only one report of a human death caused by a stingray in 2018. Only two have been reportedly recorded in Australia since World War II - including 'Crocodile Hunter' Steve Irwin.

Their research was published last week in journal Endangered Species Research.