This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: To what extent does bottom trawling impact the seafloor of the Baltic Sea—and how quickly does it recover? Two new studies from the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) show that the marks on the seafloor provide a much clearer picture of the actual impact than vessel position data alone.
Using high-resolution echo sounder measurements and AI, the researchers reveal previously insufficiently recorded impacts and also document surprisingly rapid changes of the seafloor condition. Furthermore, they found strong indications of fishing violations in a marine protected area. The study results were published in the journals Ecological Informatics and Anthropocene.
Bottom trawling is one of the most significant forms of direct human interference with the seafloor. Nets are dragged along the bottom, and heavy net-opening devices—known as "otter boards"—in particular can leave deep furrows. This stirs up sediments, alters habitats and harms benthic organisms.
However, it is often difficult to determine the extent to which individual marine areas are affected. Standard methods of monitoring fishing activity based on Automatic Identification System (AIS) vessel data have gaps: Smaller fishing vessels, which play an important role in the western Baltic Sea, are not reliably detected by established monitoring systems. A team including IOW marine geoscientists Mischa Schönke and Peter Feldens and scientists from the Thünen Institute of Baltic Sea Fisheries has therefore adopted a different approach: Rather than just investigating where fishing vessels have been operating, the researchers analyzed the fishing gear marks on the seafloor.
Their research shows how this can be used to record spatial and temporal changes in trawl marks and to gain new insights into the regeneration of the seabed. "AIS vessel position data tell us where fishing boats have been active. However, they do not necessarily reveal the extent to which the seafloor was actually impacted.
The marks in the sediment, on the other hand, provide us with direct evidence of physical changes—even in areas where information on fishing activities is patchy," explains Schönke, lead author of the study published in Ecological Informatics. Fishing intensity in the western Baltic Sea has changed significantly in recent years. In particular, due to the largely discontinued fishing for cod, bottom trawling declined markedly in many areas from 2022 onward.
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