Mussels: advancements in sustainable cultivation and research at WU
Mussel farming, a vital industry in the Netherlands, is undergoing significant innovation and expansion. From offshore wind park cultivation to improved ecological practices, researchers and industry professionals are collaborating to enhance sustainability and efficiency in the sector.
Mussel production, particularly in protected areas such as the Wadden Sea and Eastern Scheldt, operates under stringent regulations. Over the past two decades, programs like EVA-II (2000–2004) and PRODUS (2009–2012) have driven the transition from traditional dredging to more sustainable seed mussel collection systems. These changes are part of the 2008 Mussel Covenant, which seeks to reduce bottom fishing and promote environmentally friendly alternatives.
The ongoing KOMPRO (Knowledge and Research for Mussel Production) project, a partnership between researchers and mussel farmers, focuses on permits, farming practices, societal acceptance, and rapid responses to industry challenges. It includes monitoring shellfish stock dynamics, exploring optimal mussel densities, and studying the impact of predators like crabs and starfish.
A pilot project in the Borssele Wind Park, 55 kilometers off the Dutch coast, is testing offshore mussel farming in high-energy environments. Developed by steel construction firm OOS, the farm utilizes adjustable-depth steel rafts to cultivate mussels. Crustacean researcher Pauline Kamermans explained that this system minimizes damage from rough seas by lowering the farm below wave level.
The farm's design features horizontal wires with vertical droppers where mussel larvae attach and grow. Early results indicate varying growth rates depending on depth. Mussels grown at three meters perform better than those near the surface due to reduced energy expenditure in turbulent waters.
Researchers are also studying the seabed beneath offshore farms to monitor the formation of natural shellfish banks from fallen mussels. These structures could boost marine biodiversity. Meanwhile, Wageningen Economic Research is evaluating the economic feasibility of offshore farming, including taste tests and market analysis. The initiative is part of the EU-funded ULTFarms project, which includes similar trials in Belgium, Germany, and Denmark.
Closer to shore, the Voordelta region has emerged as a promising area for mussel farming due to its ample space and nutrient-rich waters. Initial harvests revealed that deeper water provides a better growth environment, as mussels expend less energy holding onto farming structures. Addy Risseeuw, from the Producers' Organization for Mussel Cultivation, noted that these trials align with the Mussel Covenant's goal to shift cultivation from the seabed to the water column.
However, challenges remain. The costs of water-column farming are significantly higher, and weather conditions at sea make harvesting difficult. Jacob Capelle, a researcher at Wageningen University & Research, emphasized the need for specialized equipment to improve accessibility and efficiency.
The Wadden Sea has seen a notable increase in young mussel banks, adding approximately 4,000 hectares in 2023. Marine biologist Karin Troost from Wageningen University attributed this to a decline in predators like shrimp and favorable salinity conditions. These new mussel beds benefit the entire ecosystem, providing food for birds and shelter for marine life. However, their survival depends on weather conditions, as winter storms can significantly reduce the population.
Mussels offer a range of ecosystem services, including water purification, biodiversity enhancement, and coastal defense. A recent Wageningen study calculated the "true price" of Dutch mussels, factoring in environmental costs and benefits. The study found that while mussels contribute 0.14 euro per kilogram to natural capital through water filtration and biodiversity, outdated diesel-powered vessels in the industry present environmental challenges.