To get an estimate on how many sea creatures are becoming tangled in plastic waste in the world’s oceans a team of University of Exeter scientists compiled all existing published studies and Twitter posts they could find on shark and ray entanglements. They found well over 1,000 different reports on entangled individuals! What’s worse is that they believe the true number is actually far higher since not many studies have focused on plastic entanglement among shark and rays. The research has been published in the journal Endangered Species Research.
Most of these entanglements involve lost or discarded fishing gear. As tragic as this is, it is a “far lesser threat” to sharks and rays than commercial fishing. Nevertheless, the suffering it causes is still a major animal welfare concern.
Kristian Parton, of the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall, said:
One example in the study is a shortfin mako shark with fishing rope wrapped tightly around it. 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.
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. Additionally, there’s a real animal welfare issue because entanglements can cause pain, suffering and even death.
Co-author Professor Brendan Godley, a coordinator of the university’s marine strategy, added:
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. 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.
From all the data they collected, 559 animals from 26 shark and ray species, great white, basking, tiger, and whale sharks were found from Twitter reports; while 557 individuals from 34 species, nearly 60% of those cases involved spotted dogfish, spiny dogfish and spotted ratfish, were found from the academic papers.
Both data sources suggested “ghost” fishing gear (nets, lines, and other equipment lost or abandoned) were by far the most common entangling objects, followed by items included strapping bands used in packaging, polythene bags, and rubber tires.
According to a press release, the study identifies the following factors that appear to put certain species more 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.
As a continuation of their research, the scientists have worked with the Shark Trust to create an online report form to gather data on entanglements. That report can be seen HERE.
This research is a welcome reminder that what we do has an effect on all the creatures around us and we have a responsibility not just for the survival of our species, but for the wellbeing of the others too.
