Standfirst: More than 6,000 concrete blocks and thousands of synthetic ropes have been removed from Greek waters through the Fishing For Litter programme. The waste is linked to an illegal fishing practice that can damage marine habitats, vessels and fishing equipment.
More than 6,000 concrete blocks have been recovered from the seabed in Greek waters since 2019, highlighting the lasting environmental cost of abandoned fishing equipment in the Mediterranean. The material is being collected through the Fishing For Litter programme, operated by the Athanasios C. Laskaridis Public Benefit Foundation in partnership with environmental organisation iSea.
The programme has also recorded around 11,700 synthetic ropes associated with fishing activity. Participating vessels remove waste from deep waters while carrying out their normal work, giving researchers a clearer picture of the scale and location of marine pollution.
What the Greek seabed clean-up has found
According to figures provided by iSea, the programme has recovered 6,278 concrete blocks and approximately 11,700 ropes since it began. Fishing vessels involved have removed more than 360 tonnes of waste from Greek waters.
Plastic accounts for more than 83 per cent of the material collected, while abandoned fishing gear represents 34 per cent. The largest concentrations of the concrete blocks and ropes have been identified in:
- the Euboean Gulf;
- the Thracian Sea; and
- the Thermaic Gulf.
The initiative is continuing across Greece, with 67 fishing vessels taking part and operations covering a wider area than in earlier years.
How concrete blocks are abandoned at sea
The waste is associated with night-time fishing using traditional Mediterranean vessels known as gri-gri boats. These operations use floating light devices, sometimes called “robots”, to attract and concentrate fish near the fishing vessel.
The devices must be kept stable in the water. Under the prescribed method, they are secured with suitable anchors and retrieved once fishing has finished. The equipment is meant to be brought back on board gradually, together with the anchoring system.
iSea says that, in some cases, crews instead use concrete blocks attached to polypropylene ropes. Typically, two blocks are used for each light device. When fishing ends, the ropes may be cut so that the floating equipment returns quickly to the main vessel.
The light devices are recovered, but the blocks and severed ropes remain on the seabed. A time-saving practice therefore creates persistent underwater waste.
Why the blocks are difficult to detect
Many of the blocks are found only after becoming caught in fishing nets. The recovered items weigh approximately four to five kilograms each, meaning the 6,278 blocks recorded by the programme represent several dozen tonnes of concrete that had been left underwater.
The total amount may be higher because the programme records only the material brought to the surface and reported through its collection work. The figures therefore provide an important indication of the problem rather than a complete inventory of all abandoned fishing equipment.
Risks to marine life, boats and fishing gear
Abandoned fishing gear is a significant form of marine litter because it can remain active or hazardous long after it has been discarded. Ropes may continue to entangle marine animals, while their movement through the water can create risks for vessels.
Polypropylene ropes can also break down into smaller plastic particles. These microplastics may enter marine food chains when ingested by fish and other organisms. Concrete blocks, meanwhile, settle directly on the seabed and can disturb habitats and organisms living there.
The material also creates practical risks for the fishing industry:
- ropes can become caught around boat propellers;
- concrete blocks can damage nets and other equipment;
- entanglement can endanger marine wildlife; and
- blocks caught in nets can damage or destroy part of a catch.
These impacts add to existing pressures from overfishing, plastic pollution and habitat degradation in coastal waters.
Calls for stronger enforcement in Greek waters
iSea argues that removing waste after it has been abandoned is not enough to solve the problem. The organisation has called for more systematic enforcement of existing rules and clearer legal definitions covering the equipment used in gri-gri fishing.
Suggested measures include:
- more inspections carried out at sea;
- checks on vessels as they leave and return to port;
- penalties where illegal anchoring practices are confirmed; and
- clearer rules on auxiliary light devices and their anchoring systems.
Clearer descriptions in legislation could help distinguish lawful equipment from practices that leave ropes and blocks behind. Better monitoring would also make it easier to identify the sources of marine litter before it spreads across wider areas.
Why this matters beyond Greece
The Greek clean-up illustrates a wider European environmental challenge: fishing gear can become marine pollution when it is lost, abandoned or deliberately discarded. Because waste moves through coastal waters and marine ecosystems cross national boundaries, prevention and recovery can have relevance beyond the waters where material is first found.
For Greece, the immediate issue is the condition of its gulfs and seas and the safety of local fishing activity. For the wider region, the findings underline the importance of responsible fishing practices, effective port controls and cooperation between fishers, environmental groups and public authorities.
The Fishing For Litter programme shows how working fishing vessels can contribute to marine clean-up operations. Its recorded recoveries also demonstrate that prevention remains more effective than relying on nets and crews to remove waste after it reaches the seabed.
What happens next?
The programme is continuing in Greece with expanded participation and geographical coverage. Further recoveries may improve understanding of where the waste is concentrated and how much is linked to specific fishing practices.
The longer-term response will depend on enforcement of existing requirements, clearer rules for light-based fishing equipment and cooperation with fishing communities. The central takeaway from the Greek experience is straightforward: removing abandoned gear is essential, but stopping it from being left behind is the most effective way to protect marine ecosystems.
