Cheaper, easier eDNA testing shows similar results to bottom-trawl surveys

Published on
December 31, 2020

A recent study says that environmental DNA (eDNA) has the potential to be a far cheaper and less environmentally destructive alternative to traditional bottom trawl surveys. 

The study, published recently in ICES Journal of Marine Science, found large-scale comparisons of eDNA testing results and traditional bottom-trawl surveys yielded similar stock assessment data.

Last year, researchers from the Rockefeller University, Monmouth University, and New Jersey’s Bureau of Marine Fisheries joined the New Jersey Bottom Trawl Survey on four different occasions, collecting water in the same area where researchers were conducting trawl surveys. They found that eDNA testing identified 92 to 100 percent of the abundant species detected by trawl surveys, and up to 82 percent of all species.

“In this one-year study, eDNA reporting largely concorded with monthly trawl estimates of marine fish species richness, composition, seasonality, and relative abundance. Piggybacking eDNA onto an existing survey provided a relatively low-cost approach to better understand eDNA for marine fish stock assessment,” the report states.

The big difference between the methods is that bottom trawls require boats to drag large nets across the seafloor, while eDNA samples can be collected by simply scooping up buckets of water. The eDNA testing itself “can be performed rapidly over large scale by non-experts with modest equipment."   

The paper’s lead author was Rockefeller University environmental genetics researcher Mark Stoeckle. According to the report, this is only the third study that directly compares eDNA to bottom trawls. The report goes on to note that “realizing this promise awaits better understanding of how eDNA relates to fish presence and abundance.” 

"It's really going to be a game change for ocean science, with many applications,” Stoeckle told ABC News.

The paper postulates that eDNA could even prove to be more accurate, as bottom-trawl captures can be inconsistent, influenced by the type and mesh size of nets used, as well as other factors like species avoidance and distribution.

Other survey alternatives like unmanned sail drones, which were used in Alaska’s Bering Sea this summer when surveys were suspended over coronavirus concerns, have proved to be cost prohibitive.

Photo courtesy of Anney_Lier/Shutterstock

Contributing Editor reporting from Seattle, USA

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