The spatial combination of a sea farm – where mussels, oysters and seaweed grow – and passive fishing with innovative baiting techniques has been extensively tested off our coast in the past three years. That it succeeds is good news, because both activities, unlike traditional (active) beam trawling, are allowed in wind farm zones. Light, sound and smell appear to be successful techniques for catching more cuttlefish, shrimp and fish on the bottom of a multi-species sea farm. Additionally, tools have been developed 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 24 November 2022 in Ostend by project partners Colruyt Group, Brevisco, AtSeaNova, Flemish Fish Auction, the Institute for Agricultural, Fisheries and Food Research (ILVO) and the Royal Belgian Institute of Natural Sciences (RBINS).
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. We import 70% of our marine food in Europe, which illustrates 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 in Pots with 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 type of fibers, the scientists caught 10 times more cuttlefish.
- Other techniques that significantly increased catches were the use of LED lights in pots for gray and sturgeon shrimp, sounds of eating in pots for roundfish and the smell of banana in pots for flatfish.
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 Catches Score Well on Quality and Taste
SYMAPA partner Vlaamse Visveiling (Flemish Fish Auction) 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: extremely 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.
The North Sea is a well-monitored ecosystem. RBINS but also ILVO and several European partners collect data to monitor the health of fish stocks and of the wider marine ecosystem. RBINS also designed useful tools for planning sea trips. A platform for five-day marine forecasts on tides, wind speeds, wave height, etc., was already in place (the Marine Forecasting Centre), but thanks to SYMAPA and the EU-H2020 FORCOAST-project there is now also a modelling tool to predict the best period for the installation of splash collectors. With those devices, cultivators collect stray seeds of mussels and oysters for subsequent rearing. Too-early placement can cause the nuisance of fouling; too-late placement can ruin the harvest.
Léo Barbut and Geneviève Lacroix (RBINS): “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 to be stable and “North Sea-proof”.
High Quality Oysters from the Belgian North Sea
The past project Value@Sea demonstrated that the endangered European 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.
Colruyt Group remains committed to research to eventually grow flat oysters in the Westdiep zone. 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 and combining activities also has some operational advantages. The applications in Westdiep Sea Farm 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 persisting technical challenge. In SYMAPA, both horizontal and vertical structures were tested by partner AtSeaNova. Horizontal structures perform 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.
Useful data for 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 Westdiep and wind farm zones. Passive fishing is also allowed in both, unlike classic beam trawling which is not allowed around the windmills.
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.”
Article largely based on ILVO press release, 24 November 2022