Scientists at the University of Exeter have found hundreds of sharks and rays have been entangled in plastic.
The scientists scoured academic papers and Twitter and found reports of 557 individual sharks and rays entangled in plastic in the Atlantic, Pacific and Indian oceans.
On Twitter, the scientists found 74 instances of shark and ray entanglements impacting 559 individual sharks and rays from 26 species including whale sharks, great whites, tiger sharks and basking sharks.
The true number is likely higher since there haven't been many studies focused on plastic entanglement of sharks and rays. Most of the entanglements were the result of lost or discarded fishing nets. And while its less of a threat than commercial fishing to sharks and rays, it's clearly causing suffering.
“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," the scientists from the University of Exeter said in a press release announcing the results of the study. “Additionally, there’s a real animal welfare issue because entanglements can cause pain, suffering and even death.”
Fishing Gear Among the Biggest Culprits
The scientists pointed to one entanglement in which a shortfin mako shark had fishing rope tightly wrapped around it. The shark had grown during the entanglement with the barnacle-covered rope dug into the skin, causing damage to the spine.
Both data points, research and Twitter, suggested abandoned fishing gear by far was to blame. Strapping bands, polythene bags, and rubber tyres also caused some of the entanglements.
Sharks In Open Oceans Most at Risk
Based on the research the scientists found sharks and rays in the open ocean are at more risk of being entangled as are those living on the seafloor. Species that cover long distances are also at more risk of running into plastic waste.
Sharks are at more risk than rays because of their body shapes. The researchers said species with unusual features including manta rays, basking sharks and sawfish face more danger.
“Due to the threats of direct over-fishing 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," said Co-author Professor Brendan Godley, co-ordinator of the university’s marine strategy in the release. “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.”
The scientists said more research needs to be done and created an online report form for data gathering.