Hundreds of sharks and rays entangled in plastic debris discarded by humans – study
More than a thousand sharks and rays are known to have become entangled in plastic debris with “significantly greater number of species” likely to be affected, a study found.
Scientists at the University of Exeter found reports of 1,116 of the creatures caught up in plastic in the world’s oceans after scouring existing studies and social media.
The true number is likely to be far higher, the researchers said, calling debris from land-based pollution and discarded fishing gear a “severely under-reported threat”.
The researchers reviewed existing studies and also appealed for information on Twitter, fearing that the issue had been pushed “under the radar” by threats such as over-fishing.
Co-author Professor Brendan Godley, co-ordinator of the university’s marine strategy, said: “Due to the threats of direct overfishing of sharks and rays, and ‘bycatch’ (accidental catching while fishing for other species), the issue of entanglement has perhaps gone a little under the radar.
“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.”
Dozens of species were affected including whale sharks, great whites, tiger sharks and basking sharks.
The majority of the entanglements involved abandoned, lost or discarded fishing equipment, known as ghost fishing gear.
There were also reports of the creatures, which are classed as elasmobranchs, trapped in plastic packing straps, bags, packaging, elastic cords and clothing.
The scientists acknowledged that entanglement is a “far lesser threat” than commercial fishing, but said it remains a “major animal welfare concern”, with possible conservation implications.
Authors of the study, published in Endangered Species Research, wrote: “If elasmobranchs are susceptible to entanglement in anthropogenic debris, this could have potential negative implications on rapidly declining populations.
“Entanglement can lead to starvation, suffocation, immobilisation and ultimately death, making this unequivocally an animal welfare issue, if not of conservation relevance.”
They said that there were alarmed to see reports regarding whale shark entanglement made on social media, compared to none in published studies.
They added: “This emphasises that entanglement is more than likely impacting a significantly greater number of species on a vastly larger scale than this review has presented.”
They are calling for a “citizen science platform” to be set up via a website or smartphone app to help crowdsource reports.
The researchers have worked with the Shark Trust, a Plymouth-based charity, to create an online report form to gather data on entanglements.