Bottom Trawling and Fish Welfare: Decompression, Injury, and Bycatch

Bottom trawling captures fish in ways that cause acute physical injury and death from decompression trauma, with welfare implications for billions of fish annually.

Key Facts

Bottom trawling accounts for approximately 25% of global wild fish catch
Fish hauled rapidly from depth experience decompression — swim bladder rupture and organ damage
Bycatch in trawl fisheries can equal or exceed target species catch in some areas
Beam trawls dragged across the seabed cause direct mortality of benthic invertebrates
Several countries and the EU have proposed restrictions or bans on bottom trawling in marine protected areas

Welfare Considerations

Fish caught in bottom trawls experience a cascade of physical harms. Rapid pressure changes during hauling rupture swim bladders and cause hemorrhage. Crushing from the weight of catch above causes skeletal fractures. Asphyxiation begins as soon as fish are removed from water. For deepwater species, decompression injury is severe — eyes protrude, organs herniate, and fish may be dead before the net reaches the surface. The welfare case for reducing trawl fishing is compounded by its ecological destruction of seafloor habitats.

What You Can Do

Choose MSC-certified fish from non-trawl methods including line, trap, or seine where possible
Support campaigns for bottom trawling bans in marine protected areas
Reduce consumption of species predominantly caught by trawl including prawns and flatfish
Advocate for transition funding for trawl fishers moving to more selective methods
Support sustainable fisheries research and monitoring organizations