Ecomare

Dieren en planten

Water en land

Mens en Milieu

Mussels

size:

up to 8 centimeters, sometimes up to 15 centimeters

age

usually 2-3 years, maximum 24 years

color:

blue-gray or brown

food:

plankton

enemies:

crabs, birds, starfish, fisheries

reproduction:

sexual

Dut: Mossel
Lat: Mytilus edulis
Eng: Common mussel (blue mussel)
Ger: Miesmuschel
Fre: Moule
Dan: Blimusling

Mussel

Mussels are found in large quantities along the Dutch coastline. People collect the mussels from natural beds or farm them for consumption on mussel lots in the Wadden Sea and delta region. In addition to people, shorebirds such as herring gulls and eider ducks also like to eat mussels. Mussels attach themselves to stones or shells with the help of strong threads, known as the mussel's 'beard'. For man and animal alike, it can be quite a job loosening a mussel from a stone. The threads keep the mussel in place so that it isn't affected by movement in the water.

Pacific oysters
The arrival of the Pacific oyster in the Wadden Sea used to be seen as a threat for mussel banks. Pacific oysters eat lots of plankton, including larvae from other shellfish. Furthermore, they take up a lot of space. In just a few years, many of the mussel banks in the Wadden Sea were overgrown with Pacific oysters.

Biologists were concerned that the mussel would become much rarer due to competition with Pacific oysters. Consequently, shellfish-consuming birds, such as eiders and oystercatchers, would run into food shortages. However, it now appears that older oyster reefs have become very suitable underground for mussels and that the two species have no problem living together. We now see mixed shellfish banks in many areas.
Vulnerable mussel banks
Mussel larvae can live in huge numbers in areas where there is sufficient food. This is how a mussel bank eventually forms. Many other marine animals live among the mussels, such as sea anemones, polyps and gobies. Mussel banks are vulnerable. In the Wadden Sea, most of the old banks were fished up by mussel fishermen. They scraped the banks in order to collect young mussels. This is what they call mussel seed and they use them to cultivate this shellfish on the mussel plots. According to the fishermen, storms are also the cause of the disappearance of the banks. Nowadays, fishing mussel seed is no longer permitted everywhere.
Distribution and habitat
Mussel bank, Sytske Dijksen, www.fotofitis.nl
©
Mussels are found in large quantities along the Dutch coastline. They are cultivated in the Wadden Sea and delta region. Mussels live on banks at depths between the average high-tide level and 5 meters deep.
The young mussel
Development of a mussel, Iris Hendriks, NIOO, Yerseke
©
Mussels lay millions of eggs in the spring. Fertilization takes place in open water. Afterwards, a larva with shell develops within a few days from the fertilized egg cell. Because the small shell looks a lot like a capital D, the mussel is also called a D-larva at this stage (see photo). This larva has a kind of sail which it used to swim through the water. After 2 or 3 weeks, this sail disappears and the larva develops a foot.

A young mussel needs a hard surface upon which to attach itself with its byssus (threads). The hard substrate can be a rock, a dike, a pole, a wreck or a piece of marine litter. Inhabited or empty shells (for example, from the sand gaper) also offer sufficient grip. Breakwaters are often totally overgrown with a layer of mussel seed.
Vulnerable mussel banks
Mussel bank, Ecomare
©
Mussel larvae can live in huge numbers in areas where there is sufficient food. This is how a mussel bank eventually forms. Many other marine animals live among the mussels, such as sea anemones, polyps and gobies. Mussel banks are vulnerable. In the Wadden Sea, most of the old banks were fished up by mussel fishermen. They scraped the banks in order to collect young mussels. This is what they call mussel seed and they use them to cultivate this shellfish on the mussel plots. According to the fishermen, storms are also the cause of the disappearance of the banks. Nowadays, fishing mussel seed is no longer permitted everywhere.
Pacific oysters
The arrival of the Pacific oyster in the Wadden Sea used to be seen as a threat for mussel banks. Pacific oysters eat lots of plankton, including larvae from other shellfish. Furthermore, they take up a lot of space. In just a few years, many of the mussel banks in the Wadden Sea were overgrown with Pacific oysters.

Biologists were concerned that the mussel would become much rarer due to competition with Pacific oysters. Consequently, shellfish-consuming birds, such as eiders and oystercatchers, would run into food shortages. However, it now appears that older oyster reefs have become very suitable underground for mussels and that the two species have no problem living together. We now see mixed shellfish banks in many areas.