Image © Howard Wood / COAST
Humanity’s most popular industrial-scale method for catching fish is also one of the most destructive.
Bottom trawlers, vessels that drag weighted nets over the seabed to scrape up seafood, land around 19 million tons of seafood annually. This is almost a quarter of global marine landings and is an amount larger than any other fishing method. In some parts of the world over half of all seafood landed is caught in this way.
How does it work?
Trawling is the practice of dragging a weighted fishing net (a trawl) through the ocean in an effort to catch seafood.
Bottom trawling is when the net is towed along, or very near to, the seafloor to catch bottom-living fish like flounder, plaice and halibut, as well as semi-pelagic species such as cod, squid and rockfish.
It is different from midwater trawling, which targets pelagic fish (those that live in the upper water column) like mackerel, anchovy, herring and hoki. Midwater trawlers usually fish for a single species, whereas bottom trawlers target multiple species.
Want to know more?
Bottom trawling can be hugely devastating for marine ecosystems and those who rely upon them to eat and to live.
Trawl nets as wide as a football field plough up the seabed, destroying vast amounts of marine life. Fragile habitats that provide food and shelter for a huge and varied range of sea creatures can be ripped to shreds. Many never recover.
Over the past 65 years alone, bottom trawlers have discarded overboard more than 400 million tonnes of untargeted marine life.
This includes everything from protected species and marine megafauna to commercially valuable fish also targeted by small-scale fishers. Had this catch been landed, it would have been worth around US$560 billion.
Over 100 million people rely on inshore subsistence and small-scale artisanal fishing for their daily food and livelihood − often using the same waters targeted by destructive trawlers.
The destruction wrought by bottom trawling goes much deeper than the glaring loss of marine life. By pulverising complex habitats and undermining fish populations, bottom trawling creates conflict and diminishes fisheries that are critical to the livelihoods and food security of some of the most vulnerable people on earth.
Every year, bottom trawling releases one billion tons of CO2 from the seabed, an amount that some have equated to emissions from the entire aviation sector.
The marine sediments disturbed by trawl nets are the world’s largest carbon stores. Bottom trawling releases carbon from the seabed into the water, increasing ocean acidification, and further undermining productivity and biodiversity. Plus there are the emissions from the trawlers themselves, which are among the highest of any method of food production.
We want to see bottom trawling urgently tackled by all coastal nations, with evidence of a globally reduced footprint by 2030.
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