We all have in our heads the typical image of a turtle entangled in a plastic fishing net or of the fish caught in the rings used to pack cans. However, it is difficult to know how many animals in particular are affected by the problem of the presence of plastic in the oceans , but quantifying its impact is important to remedy it.
Now, a team of scientists from the University of Exeter has published a work in which they estimate the number of sharks and rays entangled in plastic, or at least the reported cases, as the number is expected to be much higher. The researchers focused on reviewing the scientific studies published with this type of data to date, and also on the notices given through social networks, specifically Twitter.
The authors of the research, which is published in the journal Endangered Species Research , point out that, although the biggest problem for these species is not getting trapped in plastic – the impact of commercial fishing on their populations is much greater -, It is precisely for this reason that the study of the effect of plastic has been relegated to the background and there is not much information about it.
“While we do not believe that becoming entangled in debris is a significant risk to the future of sharks and rays, it is important to understand the variety of impacts faced by populations of these species, which are among the most threatened of the species. oceans “, explains Kristian Parton, one of the signatories of the work.” In addition, it is a real problem of animal welfare , because entanglements can cause pain, suffering and even death, “he adds.
One of the examples given by the authors is that of the mako shark, or short-finned shark ( Isurus oxyrinchus ) that was trapped in an old traditional fishing line (see image at the top). “The shark had continued to grow even after becoming entangled, so the rope, which was covered in barnacles, had gotten into its skin and damaged its spinal column ,” adds the researcher.
Alarms via Twitter
The authors emphasize that their work has pioneered the use of the social network Twitter to collect information on notices of sightings of animals trapped in plastic. “The results revealed appointments of individuals in places that had not been previously recorded in academic articles,” explains Brendan Godley, another of the researchers participating in the work.
On Twitter, the researchers found reports of entanglement involving 559 individuals belonging to 26 species of sharks and rays. On the other hand, the review of academic documents found reports of 557 sharks and rays entangled in plastic, covering 34 species in the Atlantic, Indian and Pacific oceans.
The most dangerous objects
Both data sources suggested that, in general, the majority of animals became entangled in abandoned fishing gear. Other items included items used in packaging processes, polyethylene bags, and rubber tires.
Risk factor’s
The study identified the biggest risk factors for getting caught in plastic:
- Habitat : sharks and rays that live in the open ocean, as well as those that frequent the seabed.
- Migrations: species that cover great distances
- Body shape: Sharks appear to be more likely to entangle than rays. Other species with special characteristics that are more at risk are stingrays, basking sharks and sawfish.
Citizen science
The authors insist that much more information is needed to know the real impacts of plastic on these species, and they have worked with the Shark Trust entity to create an online form that allows to easily report sightings of species trapped in any corner of the planet.
Photo: Daniel Cartamil
