Press release Combination of passive fishing and marine aquaculture step closer to profitable practice


The SYMAPA project delivers innovations in shellfish culture, a toolkit for successful baiting techniques for passive fishing, and tools for smart aquafarming.

The spatial combination of a sea farm where mussels, oysters and seaweed grow with passive fishing through innovative baiting techniques has been extensively tested off our coast for the past three years. That it succeeds is good news, because both activities, unlike traditional (active) beam trawling, are allowed in zones in front of wind farms. Light, sound and smell appear to be successful techniques for catching more squid (cuttlefish), shrimp and fish on the bottom of a multi-species sea farm. Data scientists have also developed tools that allow sea farm operators to better plan sea trips. The results of the VLAIO and Blue Cluster project SYMAPA were presented to press and stakeholders on Thursday in Ostend by project partners Colruyt Group, Brevisco, AtSeaNova, Flemish Fish Auction, Institute for Agricultural, Fisheries and Food Research (ILVO) and The Royal Belgian Institute of Natural Sciences (KBIN).

North Sea Minister Vincent Van Quickenborne was there:

"We are going to develop the Belgian part of the North Sea as the powerhouse of our country and as an engine of innovation and self-sufficiency. Therefore, in addition to wind farms and floating solar panels, we also want to cultivate seaweed in the North Sea to make biofuel. For this we have allocated 250,000 euros of research money. In the wind farms we can produce food in addition to energy. If you know that in Europe we import 70% of our marine food, this proves that there is still a lot of potential in our country for mariculture and passive fishing. Proteins extracted in this way from seaweed or shellfish no longer need to be produced through animal husbandry or fishing. The results of the SYMAPA project show that important steps have been taken to make it not only technically and biologically but also economically feasible to combine not one, but two or even three activities in the same North Sea zone."

10 times more cuttlefish (squid) in pots of fluorescent fibers

In passive "pot fishing," fish and other marine animals are lured to and caught in pots on the bottom of the sea. This form of selective fishing has little bycatch, little to no bottom impact and little fuel consumption. The pots are emptied regularly and the catch is alive when collected on board, which improves quality.

Fishing capacity can also be optimized through the use of light, sound and, potentially, smell. This is evident from trials conducted by ILVO in the Westdiep zone off the coast of Nieuwpoort:

  • The results for cuttlefish are impressive: by replacing the net of a standard cuttlefish pot with a fluorescent yarn, the scientists caught 10 times more cuttlefish.
  • Other techniques that significantly increased catches were use of LED lights in pots for gray and sturgeon shrimp, eating sounds in pots for roundfish and the smell of banana in pots for flatfish.
Schematische voorstelling van pottenvisserij op de bodem van de zee
Schematic representation of pot fishing on the seabed

Mattias Van Opstal and Jasper Van Vlasselaer (ILVO): "The study provided a toolkit of innovative techniques that fishermen can use to increase catch in pots. Depending on the spot in the sea and the species present there, one or the other baiting technique will be more interesting to them."

Passive capture scores well on quality and taste

SYMAPA-partner Vlaamse Visveiling is already satisfied with the quality of the passive capture strategy Sylvie Becaus (Vlaamse Visveiling): "Not only were we getting more cuttlefish in - a commercially interesting species - the quality of the products was also excellent: day fresh and not bruised."

Tests in the taste lab of the Food Pilot of ILVO and Flanders' FOOD in Melle confirmed this difference in quality: passively caught cuttlefish received better scores from the professionally trained taste panel than cuttlefish landed as bycatch in beam trawling.

Smart aquafarming

The North Sea is a well-monitored ecosystem. KBIN but also ILVO and several European partners collect data to monitor the health of fish stocks and of the wider marine ecosystem. KBIN also designed useful tools for planning sea trips. A platform for five-day mariene voorspellingen on tides, wind speeds, wave height, etc., was already in place. Thanks to SYMAPA and the EU-H2020 FORCOAST-project, there is now also a modelleringstool to predict the best period for the installation of splash collectors. With those devices, growers collect stray seeds of mussels and oysters for subsequent rearing. Placing too early can cause nuisance fouling; placing too late can ruin the seed harvest.

Léo Barbut and Geneviève Lacroix (KBIN): "Thanks to these modeling tools, we are another step closer to smart aquafarming. Operators of marine farms can use data to plan when to go to sea for maintenance of their facilities, for seed collection and ultimately for harvesting."

Mussel culture and facilities optimized

A previous project Edulis already successfully cultivated mussels between wind farms 30 to 50 km from the Belgian coast. SYMAPA coordinator Brevisco also demonstrated in the privately funded Nearshore Mussel project that large-scale mussel farming in the Belgian North Sea is technically and economically feasible. The Belgian "blue mussel" is larger and meatier (40-45% meat values) than the Zeeland mussel (30-35% meat values). It also grows faster and tastes good. In SYMAPA, the cultivation technique was optimized to the beautiful result of 16 kg of mussels per meter. Thanks to seemingly minor adjustments to the installations, there is now also no damage during storms. The installations have been made stable and "North Sea-proof.

Mosselkweek en -installaties
Mussel culture and installations

High quality oysters from the Belgian North Sea

The past project Value@Sea demonstrated that the endangered flat oyster can be cultivated in the North Sea. In SYMAPA, cultivation techniques were further refined in the Westdiep zone, with varying degrees of success. Quality flat oyster farming near the coast is possible but the rapid growth of unwanted organisms (fouling) on the baskets is a technical obstacle that must be overcome for commercially viable farming. It obstructs the flow of fresh seawater, periodically depriving the oysters of enough nutrients to grow.

Links Fouling
Left: Fouling

Colruyt Group remains committed to research to eventually grow flat oysters in Westdiep. Today, Colruyt Group is building our country's first commercial sea farm there where the first 50 mussel lines of phase 1 will be installed and the first limited harvest is expected in the summer of 2023.

Wannes Voorend (Colruyt Group): “Growing multiple species in a sea farm would allow us to offer a broader pallet of marine products, in addition, combining activities also has some operational advantages. The applications in Sea Farm Westdiep are already promising, but we are doing this in a step-by-step approach towards commercial farming.”

Quest for seaweed growing installations that can resist the North Sea currents

For seaweed, the natural conditions in the North Sea are an ongoing technical challenge. In SYMAPA, both horizontal and vertical structures were tested by partner AtSeaNova. Horizontal ones do fine on calm waves but in the North Sea the pulling force is too great. That is why they switched to vertical installations with loose suspension lines. It is these structures that are now being further tested in the ongoing EU-H2020 project UNITED.

Data from research for meaningful Marine Spatial Plan

The Belgian part of the North Sea is only 3,500 km² but interesting for a variety of activities. Think of mariculture, fishing and energy production but also shipping, sand extraction, recreation, nature and coastal protection. Planning these different activities in the Marine Spatial Plan is a difficult but important puzzle. In the current plan (2020-2026), marine aquaculture is allowed only in the 5 CIA zones for industrial uses such as Westdiep and the wind farms. Passive fishing is also allowed in both, unlike classic beam trawling which is not allowed around the windmills.

Uit Marien Ruimtelijk Plan 2020-2026
Uit Marien Ruimtelijk Plan 2020-2026

Bert Groenendaal (Brevisco), coordinator of SYMAPA: "That synergies between mariculture and passive fishing are possible is a major boost from this project. There is now a toolkit of innovative fishing techniques, mussel farming has been optimized, and there are forecasting models that also make the combination of marine activities more logistically and economically feasible."

Download photos:

Passive fisheries

Mussels and oysters

More info

Bert Groenendaal, Brevisco, SYMAPA coordinator: +32(0)495504819
Nele Jacobs, spokesperson for ILVO:, +32(0)472530696
Silja Decock, press supervisor for Colruyt Group:, +32(0)473924510
Maxim Laporte, spokesperson for Minister of the North Sea, Vincent Van Quickenborne:; +32(0)474777030


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