Research unveils cases of plastic entanglement in ocean species

A new study centers on plastic entanglement in world’s ocean, denoting that hundreds of sharks and rays are tangled in plastic waste. Team of scientists at the University of Exeter reports that there are 1000 and more entangled individual species.

According to scientists, the material of entanglement includes lost or discarded fishing gear, among others. Claiming that such material is less dangerous in comparison to commercial fishing, the entanglement has become a serious welfare concern.

Kristian Parton quotes an example of a shortfin mako shark. The shark had a fishing rope fixed tightly around its neck, concealed in barnacles. It had grown even after entanglement, with the rope dug into its skin, but the rope had damaged the shark’s 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,” says Parton, of the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

In another statement by Brendan Godley, professor and co-ordinator at the University’s marine strategy, he claimed that the problem of entanglement had become less severe owing to the more poignant issue of over-fishing and by-catch, which meant accidental catching of sharks while fishing for other species.

According to reports, the team used Twitter to collect data. Information from social media also brought such incidence of species entanglement to light, which was not recorded in academic papers.

Results from academic papers drew attention to 557 cases of plastic entanglement of sharks and rays. The results covered oceans stretching over the Atlantic, Pacific and Indian and claimed 60% of animals belonging to the species of spiny dogfish, spotted ratfish and lesser spotted dogfish. Twitter uncovered 74 cases of entanglement, with 559 individual sharks and rays, and over 26 species, which included great whites, tiger sharks, whale sharks and basking sharks.

Combined results from both the studies showed that the most common entangling objects included ghost fishing gear: a host of lines, nets and lost or abandoned fishing equipment and accessories. Another category included strapping brands, polythene bags and rubber tyres.

The study highlights that sharks and rays were more vulnerable to entanglement; with sharks, sawfish, and basking sharks more likely to be at risk, owing to their body shape. Species that migrated long distances were also vulnerable.

The study titled as ‘A global review of shark and ray entanglement in anthropogenic marine debris,’ is published in Endangered Species Research. It collaborated with the Shark Trust to gather data.