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Dieren en planten

Mussel   Bivalves   

Water en land

Mens en Milieu

Dutch shellfish fisheries   Mussel farming   Mussel seed fishery   Nature policy   Nature Protection Act   Habitat Directive   Bird Directive   
Mosselzaad, Photo Kees Groot

Mussel seed fisheries in the Netherlands

Mussels lay millions of eggs in the spring. The larva first drift freely as plankton and attach themselves to a suitable spot, as long as they haven't been eaten beforehand. After growing into a small mussel of one to two centimeters, they are referred to as mussel seed, or spat. Mussel fishermen fish this seed up from the tidal flats and place them on plots where the mussels can grow further. Fishing up muussel seed damages nature on the tidal floor. That is why more and more mussel seed is being cultivated on hanging nets, also known as mussel seed capture installations.

  • Licenses required

    Fishing mussel seed takes place twice a year, in the spring and autumn. The spring is the most important season. The fishermen are busy for three to five weeks. They must have a special license under the Nature Protection Act.

  • An end to mussel seed fisheries?

    In 2005 and 2008, the Council of State decided that the Ministry of Fisheries unrightfully issued licenses to the mussel seed fisheries. The seed fisheries on wild banks contradict the European Bird and Habitat Directives. The fishermen, the government and the nature organizations subsequently agreed to reduce seed fisheries on the tidal flats. The mussel sector has been given till 2020 to reform into a sustainable sector. In order to accomplish this, the production of mussel seed in the capture installations must grow so that the mussel farmers will have sufficient seed for the mussel plots.

  • Mussel seed capture installations
    Mussel seed project of Kees Groot, Photo: Boudewijn Winterink, Antha

    Mussel seed capture installations, also called MZIs), were first developed by Kees Groot from Den Helder. Since 2000, he has tested a new technique for harvesting mussel seed near the Balgzand. He hung seven large nets, 330 square meters, in the water. Mussel larvae attach themselves to the nets. The small seed is scraped from the nets on board the pontoon 'Kaatje Mossel'. By September 2008, there were nineteen companies with 45 installations active in the Wadden Sea and delta waters. Imares performed studies in 2007 for the best places and methods for capturing mussel seed. The western Wadden Sea and the Voordelta are the most suitable areas. Vertical nets deliver more seed than horizontal nets. The sea life in the vicinity of the MZIs changes. The shrimp fishermen catch much more fish around the installations. Natural mussel banks form as the seeds fall off the nets.

    The government has decided how many MZIs there can be in the Dutch tidal waters: 660 hectare in the western Wadden Sea, 200 hectare in the Oosterschelde and 300 hectare in the Voordelta.

  • Farming mussels

    It is also possible to cultivate mussel seed in the laboratory, starting at the egg stage. A trial project for cultivating mussel seed in large basins began on Texel and in Zeeland. There have been continual problems with toxic algae. The 'pond mussels' must then be moved to clean water. Those mussels that have been harvested are free from harmful materials.

  • Importing mussels

    Because it is sometimes difficult to find sufficient amounts of mussel seed, fishermen purchase them elsewhere. Up till 1997, a large amount of the seed came from the Irish and Celtic Seas, which were spread out in the Oosterschelde. The government forbade this import due to the danger of importing unwanted organisms. However, the European Court decided in December 2008 that in this case, there wasn't necessarily deliberate import of regionally-foreign organisms. A complicated legal jousting must now decide whether or not Irish mussels can be imported.