What is eDNA and How Can It Help Save Sharks?

Posted by TF Oren
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eDNA: four little letters, one big advancement.

A new U.K. study has found that it is possible to use traces of environmental DNA (eDNA) found in the ocean to keep track of shark populations.

These tiny, floating fragments of DNA (from the skin, blood, and excretions of animals that have passed through an area) can be used to "track" various species of sharks.

Conservation geneticist Stefano Mariani of the University of Salford says:

"It's just like when detectives do a forensic search of a crime scene, and can locate tissues and cells that contain the DNA of the suspects."

Using eDNA to monitor shark populations is superior to current methods of monitoring, which are costly, complex, invasive, time-consuming, and not always fruitful. As a result of these cumbersome methods, very little data exists on nearly half of all known shark species.


The study's lead author Judith Bakker says:

"The beauty of our method is that we can get a picture of shark diversity without the need for chasing, bating, and hooking them - so it is a lot faster for conservation scientists and less traumatic for the animals."

In the study, the team, which included scientists from six countries in Europe and the Americas, collected water samples from seven sites: four in the Caribbean and three in the Pacific Coral Sea. Then, using a process called metabarcoding, the team identified shark DNA sequences in the samples.

The eDNA collected from just a few liters of water provided valuable information not only about species diversity in certain areas, but also about population concentrations in those areas. For example, the eDNA collected from the site off the remote archipelago of Chesterfield contained the highest amount of shark DNA, suggesting that the anthropogenic impact on shark populations was less severe there than in other, more densely inhabited areas.

Bakker says:

"Sharks are vulnerable to overfishing, often have slow growth rate and low fecundity, and therefore are a flagship species in marine conservation."


Using eDNA to monitor shark populations is inexpensive and data rich. Mariani believes it is an important advancement for conservation.

He says:

"In order to protect these elusive animals and their ecosystems, we must be able to rapidly assess many areas at repeated time intervals...eDNA should prove a big step forward because basically anyone can collect water samples, and every bottle of water is a potential gold mine of data."

Although the use of eDNA is promising, there is much more to be done in terms of honing the method, including fine tuning the molecular tools used in the DNA analysis so that scientists are able to identify every species unambiguously as well as conducting further studies on how currents and depths affect the movement of eDNA.

The study was published in Scientific Reports and you can check it out here.

What do you think of this innovative new research method? Tell us in the comments section!

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What is eDNA and How Can It Help Save Sharks?