What is bottom trawling?
Bottom trawling is a fishing technique that involves dragging a large net along the seafloor to catch demersal fish—those that live near or on the bottom—such as hake, red mullet, sole, and Norway lobster.
The net is often equipped with weights or rollers to keep it close to the seabed and may have an enormous opening, supported by metal arms or hydrodynamic doors.
What problems does it cause?
If it were just a matter of selective fishing, the damage might be limited. But bottom trawling is anything but selective. It devastates the seafloor, destroying complex habitats like seagrass meadows, gorgonian forests, and sandy structures that host incredible biodiversity.
Each pass leaves a deep “furrow”—like plowing a field. Beyond habitat destruction, this practice stirs up huge amounts of sediment, releases carbon stored in the seabed, contributes to coastal erosion, and indiscriminately kills non-commercial species as well.
What does the law say?
In Europe, bottom trawling is regulated but not banned. There are depth limits, protected areas where it is prohibited, and seasonal bans. Trawling is banned within 3 nautical miles from the coast or at depths less than 50 meters.
However, exceptions are numerous, enforcement is difficult, and penalties are often ineffective. The EU’s Marine Strategy Framework Directive requires member states to achieve “Good Environmental Status” of marine waters—but bottom trawling remains one of the main obstacles.
The situation in the Mediterranean
The Mediterranean Sea is one of the most biodiverse marine ecosystems in the world—and also one of the most overexploited. Here, bottom trawling has had, and continues to have, a devastating impact.
Despite existing regulations, nets are still dragged through marine protected areas and sensitive zones. In many regions, the seabed has been literally flattened, irreversibly altering the sea’s ecological structure.
Where bottom trawling is most common in Italy
With over 7,500 kilometers of coastline, Italy has one of the largest fishing fleets in the Mediterranean. A significant part of this fleet is made up of bottom trawlers.
This technique is practiced along almost the entire Italian coastline, but it is particularly concentrated in some areas due to both tradition and economic factors. The most affected seas include:
- Adriatic Sea: The most heavily exploited basin. Bottom trawling is widespread, especially along the coasts of Emilia-Romagna, Marche, and Puglia. Its shallow, sandy seabed—seemingly “easy to work”—has been intensively trawled for decades. This pressure has led to a drastic depletion of fish stocks and the degradation of benthic habitats. The Adriatic is now one of the most overfished seas in Europe.
- Ionian Sea: In Calabria, Basilicata, and eastern Sicily, bottom trawling is a major economic activity. The sandy seabed and the presence of commercially valuable species, such as red shrimp, have led to widespread use of trawl nets.
- Central and southern Tyrrhenian Sea: Bottom trawling is common along the coasts of Lazio, Campania, and the Tyrrhenian side of Calabria, often near vulnerable areas like submarine canyons or Posidonia meadows. In Campania, illegal trawling within protected areas is a recurring issue.
- Sicilian Channel: Another critical hotspot. Deep-sea bottom trawling is practiced here, often over extremely sensitive habitats such as deep coral and sponge reefs. The ecological risk is very high, and oversight is often lacking.
Although laws prohibit bottom trawling within 3 miles of the coast or at depths less than 50 meters, these rules are frequently ignored, and violations are hard to detect.
Some marine protected areas, like the Egadi Islands, have adopted satellite monitoring systems to prevent illegal trawling, but the practice remains widespread.
Bottom trawling in Italy is not an exception—it’s a widespread practice, supported by economic incentives and deeply rooted in many coastal communities.
Change is only possible through real political will, stronger support for small-scale sustainable fishing, and increased public pressure.
The species most affected by bottom trawling in the Mediterranean
In the Mediterranean, bottom trawling targets mainly demersal species—those living in close contact with the seabed.Many are commercially valuable, but intense fishing has led to dramatic population declines, threatening both ecosystem balance and the sustainability of the fishing industry itself.
Some of the main target species include:
- European hake (Merluccius merluccius): One of the most caught species, especially in its juvenile stages. The Adriatic is a key area for hake, but stocks are severely overexploited. It’s often fished before reaching reproductive age.
- Norway lobster (Nephrops norvegicus): Highly prized commercially, it lives in burrows in muddy bottoms between 200 and 700 meters. Trawling destroys its habitat and simplifies the seafloor, making recolonization difficult.
- Red mullet (Mullus barbatus): A typical species of sandy and muddy bottoms, under heavy pressure. Its short life cycle and early capture worsen its vulnerability.
- Deepwater rose shrimp (Parapenaeus longirostris): One of the most fished deep-sea species, especially in the Sicilian Channel and Ionian Sea. Fishing pressure is extremely high, with serious consequences for non-target species sharing its habitat.
- Giant red shrimp (Aristaeomorpha foliacea): Targeted by deep-sea trawling, this species lives between 500 and 1000 meters. Intensive fishing threatens entire deep-sea ecosystems, still poorly understood but ecologically crucial.
- Other species such as groupers, seabream, John Dory, monkfish, gilthead bream, soles, rays, and benthic sharks are frequently caught as bycatch. Bottom sharks, in particular, are among the most threatened groups: their slow reproductive cycles make it impossible for populations to recover from declines.
In addition to target species, bottom trawling captures tons of non-commercial organisms (bycatch) every year—many of which die before being discarded. This massive waste of marine life contributes to irreversible biodiversity loss.
In the end, bottom trawling in the Mediterranean is not selective: it destroys habitats, removes immature specimens, and hits endangered species. In the long run, it harms not just nature but also those who depend on the sea: the fishers themselves.
Oceanic bottom trawling
Far from the coasts, in the deep ocean, the situation is even more dramatic. Industrial vessels—long as horizontal skyscrapers—drag nets spanning up to 10,000 square meters.
In a few hours, they can haul in tons of fish… and erase centuries of ecological history. Deep-sea floors, rich in coral and unknown life forms, are treated like mines to be emptied.
Why sandy ecosystems matter
When we think about protecting the seafloor, we usually imagine coral reefs, kelp forests, or underwater caves. Yet sandy bottoms—often seen as “empty” or monotonous—are among the largest and most crucial marine ecosystems on the planet.
Beneath this uniform sandy layer lies a world teeming with life: benthic sandy habitats. The term “benthic” refers to everything that lives on or near the seabed.
In sandy sediments, a rich and layered community thrives—from microscopic bacteria and protozoa to burrowing crustaceans, marine worms, echinoderms, bivalves, and flatfish.
Though less visually striking than other habitats, these ecosystems serve essential ecological functions:
- Natural filtration: many benthic organisms filter water and break down organic matter, contributing to nutrient cycling and maintaining water quality. They are the sea’s natural cleaners.
- Carbon storage: sandy sediments act as carbon sinks, storing atmospheric CO₂ in the form of biological debris. When disturbed by trawling, this carbon can be released again, contributing to climate change.
- Biodiversity nurseries: many fish species use these habitats as breeding, nursery, and shelter grounds. Without them, marine populations would struggle to reproduce and survive.
- Seafloor stability and coastal protection: benthic organisms, by burrowing and mixing sediments, help maintain the structural and dynamic balance of the seabed. Their destruction leaves coastlines more vulnerable to erosion and storm impacts.
In short, sandy seabeds are not inert wastelands—they are living systems of high ecological complexity, fragile and often overlooked.
Every time a trawl net passes through, it’s like a bulldozer crossing a flowered meadow—erasing centuries of evolution and biological interaction.
Protecting them means safeguarding the entire marine food web, the resilience of the oceans, and ultimately, ourselves.
“Plowing the sea helps”: Why comparing the seafloor to farmland is misleading
One of the most common justifications for bottom trawling is an often-repeated analogy: “Just like on land, plowing the seafloor helps new life grow.” But while evocative, this comparison is profoundly flawed. The sea is not land, and the seabed does not function like a plowed field.
On land, plowing is done intentionally to sow seeds in controlled environments with planned agricultural cycles. In the ocean, benthic ecosystems develop in delicate balance over hundreds or thousands of years—with no need for human intervention.
When a trawl net passes over a sandy bottom or a Posidonia meadow, it doesn’t “revitalize” the habitat—it destroys it. It wipes out slow or immobile organisms, alters sediment structure, stirs up clouds of particles that smother life, and releases stored carbon.
Furthermore, the supposed “positive effects” seen in the short term—like the arrival of opportunistic species after disturbance—are not signs of renewal but symptoms of imbalance. It’s like saying rats thrive after a wildfire: it’s not a sign of health, but of a degraded environment.
The idea that the seabed needs to be “plowed” is an anthropocentric and simplistic view. The ecological reality is far more complex, and every pass of a bottom trawl is one step closer to the desertification of the sea.
Deterrent methods
Are there alternatives? Yes. Some areas have been protected with artificial reefs or anti-trawling barriers—structures that physically prevent the passage of nets. In addition, technologies such as satellite radar and automated sensors are improving the monitoring of illegal activities.
But without strong political will and constant public pressure, these measures remain isolated efforts.
What we can do to end this practice
Change starts with us.
Choosing fish caught by small-scale or certified sustainable fisheries, demanding transparency about product origins, and supporting organizations that protect the ocean are all steps we can take.
And above all, we must push for a ban on bottom trawling in the most vulnerable areas. The voice of citizens can become an unstoppable wave—if it is united and informed.
Conclusion
The sea has no voice, but it leaves us signs: barren seafloors, abandoned nets, depleted coasts. Stopping bottom trawling is not a utopian dream—it’s an urgent necessity, for the health of the oceans and the future of life on Earth. We can no longer afford to ignore the scars we leave behind.
