Image: Colruyr Group

Combination of passive fishing and aquaculture at sea one step closer to a profitable practice

BELGIUM
Tuesday, November 29, 2022, 08:00 (GMT + 9)

SYMAPA project delivers innovations in shellfish farming, toolkit of 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 using innovative baiting techniques has been extensively tested off our coast over the past three years. That it succeeds is good news, because both activities are permitted in zones for wind farms, in contrast to classic (active) beam trawling. Light, sound and smell appear to be successful techniques to catch more squid (cuttlefish), shrimp and fish at the bottom of a multi-species sea farm. Data scientists have also developed tools that allow marine farm operators to better plan sea voyages. The results of the VLAIO project SYMAPA were presented to the press and stakeholders in Ostend on Thursday by the project partners Colruyt Group, Brevisco, AtSeaNova, Vlaamse Visveiling, Instituut voor Landbouw.

Minister of the North Sea Vincent Van Quickenborne was there:

“We are going to develop the Belgian part of the North Sea as the power station of our country and as a motor of innovation and self-sufficiency. That is why, in addition to wind farms and floating solar panels, we also want to grow seaweed in the North Sea to make biofuel. We have set aside 250,000 euros in research funding for this. In addition to energy, we can also produce food in the wind farms. If you know that in Europe we import 70% of our seafood, this proves that there is still a lot of potential in our country for mariculture and passive fishing. Proteins extracted from seaweed or shellfish in this way no longer have to be produced via livestock farming or fishing."

10 times more cuttlefish (squid) in jars of fluorescent yarn

In passive 'pot fishing', fish and other marine animals are lured to and caught in pots attached to buoys on the bottom of the sea. This form of selective fishing has little by-catch, little or no bottom impact and low fuel consumption. The pots are emptied every day, which improves the quality of the catch. ​

The catch capacity can also be optimized by using light, sound and potentially also smell. This has been shown by ILVO tests in the Westdiep zone off the coast of Nieuwpoort:

Schematic representation of pot fishing on the seabed

The results for cuttlefish are impressive: by replacing the net of a standard cuttlefish with a fluorescent yarn, the scientists caught 10 times more cuttlefish.

Other techniques that significantly increased the catch were the use of LED lights in pots for gray and prawns, eating sounds in pots for roundfish and the smell of banana in pots for flatfish.

Mattias Van Opstal and Jasper Van Vlasselaer (ILVO): “The research resulted in a toolkit with innovative techniques that fishermen can use to increase the catch in pots. Depending on the place in the sea and the animal species present there, one or the other lure technique will be more interesting to them.” ​

Passive catch scores well on quality and taste

SYMAPA partner Flemish Fish Auction is already satisfied with the quality of the passive catch. Sylvie Becaus (Vlaamse Visveiling) : "We not only received more cuttlefish - a commercially interesting species - the quality of the products was also excellent: fresh and not bruised."

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

Smart aqua farming

The North Sea is a well-monitored ecosystem. RBINS, but also ILVO and various European partners collect data to monitor the health of fish stocks and the broad marine ecosystem. RBINS has also developed useful tools for planning sea voyages. There was already a platform for five-day marine forecasts on tides, wind speeds, wave height, etc. Thanks to SYMAPA and the EU-H2020 FORCOAST project , there is now also a modeling tool to predict the best period for the installation of splash collectors. Growers use these devices to collect stray seed from mussels and oysters and then grow them. Placing too early can cause annoying fouling, placing too late can cause the seed harvest to fail.

Léo Barbut and Geneviève Lacroix (RBINS): “Thanks to these modeling tools, we are once again one step closer to smart aquafarming. Operators of sea farms can plan based on data when they go to sea for the maintenance of their installations, for the collection of seed and ultimately also for the harvest.”

Mussel culture and installations optimized

In a previous Edulis project, mussels were successfully cultivated 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 achieve a good result of 16 kg of mussels per metre. Thanks to apparently small adjustments to the installations, there is now no damage in the event of a storm. The installations are stable and have been made 'North Sea-proof'.

Mussel culture and installations (Photo: ILVO)

High-quality oysters from our North Sea

Photo: ILVO

The recent Value@Sea project demonstrated that the endangered flat oyster can be farmed in the North Sea. In SYMAPA, the cultivation techniques were further refined in the Westdiep zone, with varying degrees of success. Growing high-quality flat oysters 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 a commercially viable culture. It prevents the flow of fresh seawater, causing the oysters to periodically ingest too few nutrients to grow.

Colruyt Group continues to focus on research to eventually also grow flat oysters in the Westdiep. Today, Colruyt Group is building the first commercial sea farm in our country 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) : “By cultivating several species in a sea farm, we could offer a wider range of sea products, and combining activities also has some operational advantages. The applications in Zeeboerderij Westdiep are already promising, but we are doing this in a step-by-step approach towards commercial cultivation.”

Search for seaweed installations that resist North Sea currents

The natural conditions in the North Sea are a permanent technical challenge for seaweed. In SYMAPA, partner AtSeaNova tested both horizontal and vertical structures. Horizontal ones do fine on calm waves, but the pulling force is too great in the North Sea. That is why a switch was made 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 in size, but it is interesting for a variety of activities. Think of mariculture, fishing and energy production, but also shipping, sand extraction, recreation, nature and coastal protection. The planning of the various activities in the Marine Spatial Plan is a difficult but important puzzle. In the current plan (2020-2026), aquaculture at sea is only permitted in the Westdiep zone and the wind farms. Passive fishing is also allowed in both, in contrast to classic beam trawling, which is not allowed around the windmills. 

Bert Groenendaal (Brevisco), SYMAPA coordinator: “The fact that synergies between mariculture and passive fisheries are possible is an important boost for this project. There is now a toolkit with innovative fishing techniques, mussel farming has been optimized and there are prediction models that also make the combination of activities at sea more logistically and economically feasible.”

Source: Colruyt Group (translated from flemish)

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