Bottom Trawling
Definition
What 'Bottom Trawling' means
Bottom trawling involves towing weighted nets along the ocean floor to catch groundfish and shellfish. This practice crushes coral, sponge, and seagrass ecosystems, kills non-target species, and stirs up sediment that releases centuries of stored carbon, contributing to ocean acidification and biodiversity loss.
In depth
The longer answer
Bottom trawling is a commercial fishing method in which a large, cone-shaped net is dragged across the seafloor. The net's opening is held open by heavy doors or beams, and the bottom edge is weighted to maintain contact with the seabed. This technique is used to catch groundfish like cod, flounder, and shrimp, as well as scallops and other benthic species. Consumers encounter bottom-trawled seafood on menus, in supermarkets, and in canned fish products, often without any label indicating the capture method.
In practice, bottom trawling involves towing a net that can weigh several tons across the ocean floor, often at depths of 200 to 2,000 meters. The heavy gear plows through sediment, crushing or dislodging everything in its path, including corals, sponges, and buried organisms. Bycatch—unwanted fish, turtles, and marine mammals—can account for 20 to 60 percent of the catch. The trawl doors alone can create furrows up to 30 centimeters deep, and a single pass can remove decades-old habitat structures.
For consumers, choosing bottom-trawled seafood means supporting a practice that causes extensive habitat destruction and high bycatch rates. However, not all trawling is equal: some regions have banned it in sensitive areas, and modified gear can reduce seabed contact. The nuance is that many fisheries lack transparent labeling, making it difficult for shoppers to avoid bottom-trawled products. Opting for seafood certified by programs like the Marine Stewardship Council can help, though certification does not guarantee zero habitat impact.
At a glance
Quick facts
| Detail | What to know |
|---|---|
| Habitat damage | Destroys seafloor structures for decades |
| Bycatch rate | 20–60% of total catch |
| Global fuel use | Up to 20% of fishing fuel |
| Common targets | Cod, flounder, shrimp, scallops |
In practice
What this means for you
- Look for labels like 'pole-and-line,' 'trap-caught,' or 'dredge-free' to avoid bottom-trawled seafood.
- Ask your fishmonger or restaurant where and how the fish was caught; vague answers often indicate trawling.
- Choose bivalves like mussels and clams farmed on ropes or trays, which have minimal seabed impact.
- Support marine protected areas and policies that restrict bottom trawling in vulnerable habitats.
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