Up to 65% of boats anchor on Croatia’s Posidonia meadows, study finds

(Photo credit: Tino Mrčelić – Sub merus d.o.o)

Growing nautical tourism is placing increasing pressure on Croatia’s Adriatic coast, with satellite monitoring revealing that between 25% and 65% of vessels in some monitored areas were anchored directly over Posidonia oceanica meadows.

The findings come from detailed vessel distribution monitoring carried out in 2023 and 2025 as part of the Interreg BIOPRESSADRIA project. Researchers examined the Kornati National Park, the Pakleni Islands and areas of the ecological network in Dubrovnik-Neretva County, where Posidonia is a protected target habitat.

The proportion of vessels anchoring on Posidonia was lower in areas with a higher level of protection and established ecological mooring systems, such as Kornati National Park. Higher levels were recorded in areas of the ecological network, including the Pakleni Islands and Badija.

(Photo credit: Teo Baučić)

Posidonia meadows are an important part of the Adriatic marine ecosystem, but anchoring can cause significant and long-lasting damage. Boat anchors, chains and mooring systems can physically disturb the seabed and destroy seagrass, which grows extremely slowly and can take decades to recover.

Traditional mooring systems typically use large concrete blocks placed on the seabed, connected to chains, ropes and surface buoys. As boats move with wind, waves and currents, the chains can drag across the seabed, creating bare areas around the mooring point, sometimes known as the “halo effect”.

(Photo credit: Tino Mrčelić – Sub merus d.o.o)

Concrete blocks can also cover marine organisms beneath them and may remain on the seabed after a mooring system reaches the end of its useful life. Their production, transport and installation also require considerable quantities of materials, fuel and heavy equipment.

One proposed solution is the wider installation of ecological moorings, which are designed to secure boats while minimising contact with the seabed.

Instead of concrete blocks and heavy chains, these systems use geotechnical anchors, elevated seabed lines, elastic mooring lines and specialised buoys. Contact with the seabed is generally limited to the point where the anchor is installed, reducing friction and physical disturbance to surrounding habitats.

(Photo credit: Tino Mrčelić – Sub merus d.o.o)

Different types of anchors can be adapted to rock, sand, mud and other seabed conditions. Modern elastic systems can also reduce the required swing area of vessels, potentially allowing more efficient use of designated mooring areas.

Successful installation requires detailed planning, including assessment of seabed conditions, vessel numbers and sizes, appropriate anchor selection and professional installation. Regular inspection and maintenance are also necessary to ensure long-term safety and performance.

(Photo: Sunce)

The BIOPRESSADRIA project is also focusing on education and knowledge-sharing among institutions, protected-area managers, concession holders and nautical users.

As part of the project, environmental organisation Sunce participated in specialist training on ecological moorings in Dubrovnik in March and in Murter in June 2026, bringing together representatives of ministries, counties, public institutions, NGOs, concession holders and others involved in Adriatic marine protection.

(Photo: Sunce)

The project identifies ecological moorings as one of the tools that could help reduce the pressure of nautical tourism on Croatia’s sensitive marine habitats while maintaining safe and functional mooring areas for boaters.