Six Shark Species Identified By Sequencing Their DNA From Seawater

As sharks swim, they shed bits of skin and thus their DNA, that researchers can now detect. Matt9122/Shutterstock

By filtering seawater and then analyzing the DNA that is floating around in it, quite amazingly, scientists have been able to identify exactly which species of shark are living in a particular area.

The team of researchers have been using the newly emerging field of environmental DNA, also simply known as eDNA, to see if it can help them figure out what large animals are still living in highly damaged environments. Testing this out in the waters surrounding the New Caledonian archipelago in the Pacific Ocean, they found that eDNA detected an impressive 44 percent more shark species than more traditional methods.


“We have all been surprised by these results,” explained Jeremy Kiszka, one of the co-authors of the study. “It's exciting to know how useful this tool is, particularly to monitor the presence of rarer and more elusive species, which potentially includes endangered species.”

“We really hope to expand our efforts to identify critical habitats for endangered marine species using this technique.”

Publishing the results this week in Science Advances, the incredible power of this new technique is shown when you consider that the team were able to identify the presence of six different species of shark from just 22 samples of seawater, none of which had been seen during over 3,000 dives and 400 baited video traps.

The waters surrounding New Caledonia have been heavily degraded due to human activity, and so the researchers wanted to know whether or not the sharks that once patrolled the waters and now rarely seen have actually been extirpated, or simply reduced to such a low number that they have gone “dark” instead.


It has already been shown that the skin shed from large marine species such as sharks can be detected in samples taken from the water and sediment subsequently used to detect species, but this time around they were able to show how effective it was in comparison to more traditional techniques in illuminating the presence of dark species.

The most notable species they were able to find was that of the great hammerhead and the silky shark, both of which are known to be targeted for their fins. They also revealed that bull sharks are swimming these waters, a common species that had not been recorded in the area before.

The work could be a vital tool in conservation, vastly improving the ability of scientists to track and monitor threatened and elusive megafauna, and helping them to understand if species would be able to bounce back if the environment is returned to a healthier state.


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