Generally, the study supports that although entanglement is a lesser threat to sharks, in comparison to commercial fishing, the suffering causes a major animal welfare concern.
Co-author Professor Brendan Godley, co-ordinator of the university's marine strategy, reported that
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.
He continued that their study was the first to use Twitter to gather data and the results from the social media site revealed entanglements of species - and in places - not recorded in the academic papers.
Moreover, by reviewing academic papers, scientists found out reports of 557 sharks and rays entangled in plastic, spanning 34 species in oceans, including the Atlantic, Pacific and Indian. About the 60% of these animals were either lesser spotted dogfish, spotted ratfish or spiny dogfish.
In addition, via Twitter, scientists found 74 entanglement reports involving 559 individual sharks and rays from 26 species including whale sharks, great whites, tiger sharks and basking sharks.
An example in the study is a shortfin mako shark that was found with a fishing rope wrapped tightly around it, as Kristian Parton, of the Centre for Ecology and Conservation on Exeter's Penryn Campus in Cornwall, reported. He continued that the shark grew with the rope around it, resulting to the rope dug into its skin and damaging its spine.
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.
... Kristian Parton highlighted.
In addition, the study presented factors that place specific species at risk:
- Habitat - sharks and rays in the open ocean appear more likely to get entangled, as do those living on the sea floor, where materials such as nets loaded with dead fish sink and attract predators, which in turn get stuck.
- Migration - species that cover long distances appear at more at risk of encountering plastic waste.
- Body shape - sharks seem to be at greater risk than rays. Species with unusual features - such as manta rays, basking sharks and sawfish - are also at more risk.
Concluding, scientists aspire to find more on the matter and gather data; So, in collaboration with the Shark Trust they created an online report form to gather data on entanglement. To provide information, click here.