Trawling – dragging heavy gear over ocean bottoms in search of fish near the sea floor – is arguably one of the most destructive human practices. Removing fish from the sea for an ever-hungry, growing human population has consequences that include reducing fish populations and messing with the natural balance of the ocean’s food webs. In the last two decades, the secondary impacts, including reduction in species diversity and flattening of complex seafloor habitats, have started receiving more and more attention.
The heavy chains, nets and steelwork of a trawler’s fishing gears scour the ocean floor, scooping fish into the jaws of the net. They’re looking for things like flounder, cod, and shrimp, but most things in the way of the trawl either get scraped up, crushed or damaged, unless they are lucky enough to sink into a cosy burrow.
What is left after the trawl passes is a drastically altered seafloor ecosystem: a flatter, less complex habitat, with fewer invertebrate organisms and fewer fish. For those fish that manage to escape the trawl, these changes can have negative consequences for their continued growth.