DNA in Seawater Reveals Shark Presence

Reader Contribution by The Pew Charitable Trusts
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Typically, researchers have had to rely on traditional methods of tracking sharks in the oceans to study and understand their growing and moving populations, such as cameras, sensors, or direct observatory. This requires that researchers or cameras be in the exact right location at the exact right time to track the sharks, but new research may have revealed an easier way to monitor sharks in the ocean.

Environmental DNA, or eDNA, may be able to make things much easier for researchers. EDNA looks at the genetic material left behind by sea creatures, and can be used to determine what species are in or have recently been in the area. Stefano Mariani, a professor and associate dean of research at the University of Salford, United Kingdom, and a team of researchers based in France, Australia, Polynesia, and the United States conducted traditional and eDNA surveys in New Caledonia, an archipelago in the South Pacific that boasts many shark species.

This new method was able to detect more species in the area, and was also able to more accurately predict the populations of these species. This method was used in remote areas, so that the presence of humans could not affect the results, as well as more human-populated areas, both with the same level of accuracy. EDNA testing was also able to identify more species than traditional underwater visual census (UVC) samples.

On top of yielding more accurate results, testing with eDNA speeds up the process for researchers, taking three months where traditions tests can take three years to produce useful results. However, the downside to eDNA is that it cannot show the age or size of any sharks in the area.

It is important for researchers to understand the movements of sharks and their changing populations, since sharks face heavy threats from fisheries around the world, with as many as 273 million killed each year. If researchers can keep a more accurate record of shark populations, they can better understand the level of threat they the species is under, and learn how to protect it in the future.

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