July 24, 2017 — Roughly a fifth of all fish eaten globally are caught using nets towed along the bottom of the ocean. There’s long been concern that this method – known as trawling – destroys or severely damages the ecosystems where it’s used. Now, a new meta-analysis of the science available on this topic offers some quantification of the impacts of different type of trawls.
Previous studies have found that the mud plumes from some trawls can be seen from space, and that “bottom trawling related to commercial fisheries leaves a greater physical footprint on the seafloor than the combined effects of all other human activities, including scientific research, fossil fuel recovery and waste disposal.”
While it is undeniable that dragging metal gear across the seafloor impacts the ecosystems there, a new analysis of seventy different studies finds that not all trawls are equal, and that some do significantly less damage than others.
In particular, otter trawls – the type most commonly used in New England – have the least impact of the four types compared. Otter trawls scrape, on average, just under an inch off the seafloor and remove about six percent of the animals living there. In contrast, hydraulic dredges squirt water into the sediment to release buried animals, reaching about six inches into the sea floor and removing more than forty percent of animals.