Rare sharks detected around UK with DNA 'traps'

Sharks and rays rarely seen in British coastal waters have been detected by marine biologists using the DNA traces they left in their wake, reports a new academic paper.

Using eDNA surveys off the coast of Plymouth, the team from LJMU, Exeter, Bristol and the Marine Biological Association found 13 species of elasmobranchs compared to only three picked up in traditional trawl surveys.

The list includes formidible open water predators such as the porbeagle and thresher shark and the rare tope shark, listed as critically-endangered by the IUCN, along with the ‘endangered’ undulate ray.

Professor Stefano Mariani, a co-author of the study, said: “This is the first ever characterisation of shark and ray's seasonal occurrence and abundance in the South-west of England, carried out without even seeing or touching them.

“The more we know about where these fantastic fish go and at what times of year, the more we can do to protect them”

eDNA: What is that?

Environmental DNA (eDNA) is a non-invasive method of capturing information on animal species and involves collecting the fragments of DNA shed individuals as they swim through the water.

Increasingly popular, the method does no harm to the animals and is frequently more reliable than capturing or photographing the organism, as it is not biased towards the animals that are more likely to be seen or caught, hence revealing much more about whole communities. 

Prof Mariani, from the School of Biological and Environmental Sciences, who has used eDNA metabarcoding to locate marine species across the world, added: “All we have to do is collect samples of the water they swim in and that can generate fascinating ecological information.

“When you think about the spatial and temporal scalability, I don’t think there is a method that can detect more species, more efficiently and affordably than eDNA.”

The paper Environmental DNA captures elasmobranch diversity in a temperate marine ecosystem is published in the Wiley Journal Environmental DNA and authored by Zifang Liu, Rupert A Collins, Charles Baillie, Sophie Rainbird, Rachel Brittain, Andrew M Griffiths, David W Sims, Stefano Mariani and Martin J Genner.