Fish Forensics Yield Surprising Results

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TThe oceans are teeming with life, but the volume of water on our blue planet makes that life sometimes a little frustrating to find. Traditional methods of locating sea creatures – cameras, direct observation, net captures, etc. – are far from exhaustive and monitoring remote regions poses even more logistical difficulties. This means that even the most in-depth studies of ocean life will have some gaps.

Today, these gaps are filled thanks to a few infinitesimal indices.

To get a more complete picture of life in our oceans, a team of researchers turned to environmental DNA, or eDNA. These traces of DNA are left behind by marine organisms during their normal life, from fluids, excreted cells, etc. The eDNA is then recovered from seawater samples, filtered, and compared to databases to determine which animals shed them. In aquatic environments, eDNA tends to degrade relatively quickly, making it a good indicator of the presence of the species to which it belongs in the area. In total, the team’s eDNA study included more than 900 water samples from various depths ranging from the poles to the tropics, according to their study published in Biology PLOS.

Read more: »The challenge of deep-sea taxonomy»

The team, from the University of Montpellier, France, and the Center National de la Recherche Scientifique, found that the geographic ranges of more than 93% of the species detected had previously been underestimated, meaning that these species actually live over a larger territory than previously thought. Additionally, some species tolerate surprising environments. For example, the team found DNA from the crocodile icefish — a species that lives only in the frigid waters of Antarctica — as far north as Patagonia, in waters about 18 degrees Fahrenheit warmer.

These findings have important implications for ocean conservation for a very simple reason: it is impossible to fully understand the threats to marine life without first fully understanding the magnitude of marine life. With this study, our understanding of ocean life becomes a little closer.

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Main image: Marrabbio2 / Wikipedia

• Jake Currie

  Published on November 4, 2025

  Jake Currie is a writer based in Brooklyn, New York.