Every day, vast nets weighted with steel doors drag across the ocean floor — flattening coral reefs, crushing sponges, and stirring up clouds of sediment that smother everything in their path. This practice, known as bottom trawling, has become one of the most devastating forces in marine history.
What started as a way to increase fishing yields has turned into an industrial act of erasure — one that removes not only fish but the very ecosystems that sustain them.
What Bottom Trawling Is
Bottom trawling uses massive, weighted nets to scrape the seafloor for fish and shellfish such as shrimp, cod, and flounder. Each trawl can cover several square miles, removing every structure and organism in its path.
A single industrial trawler can drag a net the size of 10 football fields, sweeping through areas that took centuries or millennia to form.
While the catch is hauled up and sorted, most of what was alive below is left destroyed — crushed, buried, or dead.
The Scale of Destruction
Bottom trawling now covers an area of seabed larger than the entire United States every year. According to the UN Food and Agriculture Organization (FAO), it accounts for about one-quarter of global wild fish catches — but also for the majority of seafloor damage.
Research shows that trawling disturbs up to 2.6 million square kilometers of seabed annually, eroding biodiversity faster than any other human activity in the ocean.
How It Erases Ecosystems
1. Coral and Sponge Destruction
Many deep-sea coral reefs and sponge gardens grow only millimeters per year. When trawling gear passes over them, those structures — some hundreds or even thousands of years old — are instantly pulverized.
Deep-sea corals such as Lophelia pertusa and Paragorgia cannot regrow once destroyed. Their loss removes nursery grounds for countless fish and invertebrates, collapsing entire food webs.
2. Sediment Plumes and Suffocation
Dragging nets through sediment releases plumes of fine particles that remain suspended for days or weeks, reducing oxygen and blocking sunlight. This suffocates benthic organisms like worms, crustaceans, and small corals that live in or on the seafloor.
The process also releases stored carbon from sediments — carbon that had been locked away for centuries — making bottom trawling a hidden contributor to climate change.
3. Bycatch and Waste
Bottom trawling is notoriously indiscriminate. Up to 90% of the catch in some shrimp trawls is bycatch — fish, turtles, sponges, and corals that are discarded, often dead or dying.
This waste not only depletes fish populations but also destabilizes ecosystems by removing species critical to food web balance.
4. Habitat Loss and “Ocean Deserts”
Once trawled, the seafloor can become a flat, barren plain. Without structure, species that depend on reefs or sponge beds cannot return. Scientists call these areas “marine deserts” — lifeless zones that may never fully recover.
Biodiversity Loss on a Planetary Scale
According to a 2021 study in Nature, bottom trawling has caused a 70% reduction in deep-sea biodiversity in heavily fished regions. In some parts of the North Atlantic and Mediterranean, entire coral ecosystems have disappeared, replaced by mud and empty water columns.
Globally, trawling is now estimated to account for around 25% of total marine biodiversity loss related to human activity — a staggering toll that continues daily.
Why It Continues
- Economic inertia: Trawling is profitable for industrial fleets.
- Weak regulation: Much of the deep sea lies outside national jurisdictions, where enforcement is minimal.
- Consumer detachment: Most seafood consumers have no idea where or how their fish is caught.
Even in protected areas, illegal trawling is common. Enforcement is difficult, and penalties are often insignificant compared to profits.
Climate Impacts: Stirring Up the Carbon Sink
Trawling physically disturbs sediments that store carbon, releasing it back into the water column. Scientists estimate that bottom trawling releases up to one gigaton of CO₂ each year — roughly the same as global aviation.
This means the destruction of reefs and sponge beds doesn’t just erase ecosystems — it actively worsens the climate crisis.
What Can Be Done
1. Ban Bottom Trawling in Vulnerable and Deep-Sea Areas
Several countries — including New Zealand, Palau, and parts of Norway — have already restricted trawling in sensitive marine zones. Expanding these bans is vital.
2. Strengthen International Regulation
The high seas need stricter enforcement under UN treaties to protect biodiversity beyond national borders.
3. Support Sustainable Fisheries
Consumers can choose fish certified by sustainable programs such as MSC — and avoid products known to come from trawled sources.
4. Invest in Reef and Habitat Restoration
Damaged seabeds can sometimes be rehabilitated through coral transplants and artificial reef projects — though prevention remains far more effective than repair.
5. Reduce Global Demand
The easiest way to reduce trawling is to reduce the global appetite for cheap, mass-caught seafood. Supporting small-scale, local fisheries helps protect ocean ecosystems.
FAQs
Can trawled areas recover?
In shallow waters, some recovery is possible within decades, but deep-sea corals may take centuries — or never return.
Is bottom trawling still legal in most places?
Yes. Despite the damage, it remains legal in most of the world’s oceans, including parts of protected marine zones.
Are there alternatives to trawling?
Yes. Selective fishing gear and midwater trawls (which don’t touch the seabed) can significantly reduce habitat destruction.
Final Thoughts
Bottom trawling isn’t just fishing — it’s deforestation of the ocean floor. It destroys centuries of growth in minutes and turns thriving habitats into lifeless plains of sediment.
Each pass of a trawl net erases history: coral forests, sponge gardens, and the memory of ecosystems that once held extraordinary life.
Protecting the ocean begins by ending this silent erasure. The seabed may be out of sight, but it should never be out of mind.
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