Fishing is as old as human civilization, but industrial techniques have transformed it into one of the most destructive forces in the ocean. Among these methods, bottom trawling stands out. By dragging enormous weighted nets across the seafloor, bottom trawling doesn’t just catch fish — it crushes corals, sponges, and centuries-old deep-sea habitats in its path.
What Is Bottom Trawling?
Bottom trawling is a method of fishing where heavy nets, often large enough to swallow entire buildings, are dragged across the seafloor. The nets are held open by steel doors and weighted to stay on the bottom.
- Anything in their path is swept up: target fish, non-target species (bycatch), and seafloor structures.
- Deepwater trawls can reach depths of over 2,000 meters.
- One pass can flatten ecosystems that took centuries to form.
This makes bottom trawling one of the most damaging human activities in marine environments.
Why Coral Reefs Are Especially Vulnerable
Coral reefs — both shallow-water tropical reefs and deep-sea cold-water corals — are no match for industrial nets.
- Fragile skeletons: Coral structures are brittle. A single trawl can snap, crush, and uproot them.
- Slow growth: Many corals grow just millimeters a year. Some deep-sea corals are over 1,000 years old. Once destroyed, recovery is virtually impossible.
- Complex ecosystems: Corals provide shelter and food for countless species. When reefs are destroyed, entire food webs collapse.
Bottom trawling doesn’t just catch fish — it erases ecosystems.
The Scale of Destruction
- The UN FAO estimates bottom trawling accounts for 25% of global fisheries catch.
- Studies show up to 90% of seafloor life is destroyed in areas hit by trawling.
- Some deep-sea trawled areas resemble barren deserts after repeated passes.
- Recovery can take centuries, if it happens at all.
One pass of a trawl net can do more damage to the seafloor than a hurricane.
The Ripple Effects
Biodiversity Loss
- Bycatch kills non-target species: sharks, rays, turtles, and juvenile fish.
- Seafloor communities like sponges and anemones vanish.
- Apex predators decline when prey habitats disappear.
Carbon Release
- Seafloor sediments store massive amounts of carbon.
- Trawling stirs them up, releasing CO₂ back into the water and atmosphere.
- A 2021 study in Nature found bottom trawling may release as much CO₂ annually as global aviation.
Fisheries Collapse
- While trawling brings short-term profit, it destroys the very habitats fish need to reproduce.
- Depleted stocks lead to long-term economic losses, hitting coastal communities hardest.
Real Examples
North Atlantic: Deep-sea coral forests have been nearly wiped out by decades of trawling. Some colonies destroyed were more than a thousand years old.
Mediterranean Sea: Over 80% of assessed fish stocks are overfished, with bottom trawling a primary driver of collapse.
New Zealand and Australia: Deepwater ecosystems have been severely damaged, leading to international calls for bans on deep-sea trawling.
Why It Continues
- Subsidies: Governments provide billions in fuel subsidies to industrial fleets, making trawling economically viable even when unsustainable.
- Weak enforcement: International waters are poorly monitored, allowing destructive fleets to operate with little oversight.
- Market demand: Popular species like shrimp, cod, and flounder often come from trawl fisheries.
The practice persists because it is profitable in the short term — but the long-term costs are hidden.
Solutions and Alternatives
Policy Change
- Ban bottom trawling in vulnerable ecosystems, such as coral reefs and seamounts.
- Redirect subsidies from destructive practices to sustainable fisheries.
- Enforce stronger international agreements on high seas fishing.
Sustainable Practices
- Transition to selective fishing methods like traps, hook-and-line, or pole-and-line.
- Promote small-scale fisheries that support communities without destroying habitats.
Consumer Power
- Avoid seafood sourced from bottom trawl fisheries (especially shrimp and deep-sea species).
- Support certified sustainable seafood where standards are credible and enforce real change.
Innovation
- Technology like satellite monitoring can track and expose illegal trawling.
- Mapping seafloor ecosystems helps identify no-trawl zones for protection.
FAQs
Why can’t coral reefs recover after trawling?
Because they grow so slowly. Deep-sea corals that are centuries old can be destroyed in seconds, and regrowth may take hundreds of years.
Is bottom trawling banned anywhere?
Yes. Some countries have banned trawling in shallow waters, and international agreements restrict it in certain deep-sea regions. But large areas remain unprotected.
Is all trawling destructive?
Midwater trawling (which doesn’t touch the seafloor) has fewer impacts, but bottom trawling is consistently destructive.
What seafood comes from bottom trawling?
Shrimp, cod, haddock, flounder, and some types of crab and prawn are commonly caught this way.
Final Thoughts
Bottom trawling is one of the clearest examples of short-term gain versus long-term loss. Huge nets dragged across the seafloor flatten corals, wipe out biodiversity, and even release stored carbon back into the atmosphere.
For reefs already stressed by warming and acidification, bottom trawling is not just unsustainable — it is catastrophic. Protecting coral ecosystems means ending this destructive practice and rethinking how seafood is caught. The ocean floor is not a mine to be stripped, but a living system to be protected.
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