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Dieren en planten

Bivalves   Oysters   Flat oyster   Pacific oyster   Fauna in tidal areas   Benthic fauna   Bivalves   

Pacific oyster

size:

up to 20 centimeters, sometimes much larger

color:

white to grayish

food:

phytoplankton

enemies:

hardly any animal, but since recently gulls and oystercatchers; people and diseases

reproduction:

sexual

  • Dut: Japanse oester (creuse, wilde kreuse)
  • Lat: Crassostrea gigas
  • Eng: Pacific oyster (Japanese oyster)
  • Ger: Pazifische Auster (Felsenauster)
  • Dan: see Latin (øster)
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Pacific oysters, foto fitis, sytske dijksen

Pacific oyster

You see more and more Pacific oysters in the Wadden Sea, Oosterschelde and Grevelingen. Although they are very tasty, not everyone is happy with the presence of this oyster. You can easily cut yourself on these razor-sharp shells. And there are places where they grow in such great numbers, they drive away other shellfish. They don't just take up space, they are big eaters and leave less food for other shellfish. Although there are several disadvantages to the ever-growing Pacific oyster population, there are also advantages. The sturdy oyster reefs provide a safe refuge and a sturdy underground for various benthic animals.

  • Distribution and habitat
    japanse oester, foto fitis, sytske dijksen

    The Pacific oyster originally came from the Asian Pacific coast. It was imported by man and is now found in North America, Australia, Europe and New Zealand. In 1964, oyster nurseries imported this oyster to Zeeland. The Dutch flat oyster had suffered greatly from a disease and the fishermen hoped the Pacific oyster would be resistant. They didn't expect this species to be capable of reproducing in the cold Dutch waters, so there would be no danger in bringing this exotic animal to the Netherlands. Unfortunately, cold water did not hinder them; in the mid 1970s, the oysters had reproduced in massive numbers. The animal was imported to the Wadden Sea in 1983.

    The Pacific oyster is presently found in both the Wadden Sea and delta region, where the population is still growing. The oysters need a hard underground to grow on, but it doesn't have to be very big. An empty oyster shell is good enough for them. You find the largest reefs on sandbanks and dikes that are exposed during low tide, but you also find them growing down to depths of 80 meters.

  • Pacific oyster and consumption
    Pacific oyster in shop, foto fitis, sytske dijksen

    The Pacific oyster has been farmed on a large scale in the Oosterschelde since 1965. It is known on the Dutch market under the name 'creuse'.
    The oysters are very suitable for aquaculture. They are sexually mature at age 1 and grow very rapidly. After two years, Pacific oysters are suitable for consumption when the animal (excluding shell) weighs 100 grams. A flat oyster takes much longer to reach this weight; at age four, the flat oyster still only weighs 75 grams.

  • Ousting of mussels and cockles?
    Riff of Pacific oysters near Texel, Ecomare

    The Japanese oysters are present in massive numbers in the Oosterschelde, and they keep growing in population in the wadden region. They eat lots of algae, take up lots of space and will also eat larva from other shellfish. Biologists are concerned that the other shellfish, such as cockles and mussels, will be serious affected by this competition. In turn, shellfish-feeding birds, such as eiders and oystercatchers, could run into major problems.

    However, oyster reefs also form a kind of rocky bottom for many marine animals, such as sea anemones, barnacles and small fish that would otherwise have no suitable home in the world of sand and mud. Mussel banks used to serve this purpose, but they have become less stable than oyster reefs. In addition, they have also become more rare due to shellfish fisheries.

  • Birds and oysters

    It is not easy for a bird to crack open a Pacific oyster. Especially when they are clumped together or fastened to a stone or dike. However, scientists witnessed oystercatchers and herring gulls on Texel began to figure out how to open up these sharp, hard, thick and sturdy shells. Oystercatchers stick their bills into slightly opened oysters. If this works, then they can pry it further open and eat the meat. Gulls have found a more rigorous method. Oysters that lie loose from others are picked up with their beaks and dropped from heights onto the dikes, where they crack open. At first, the gulls were not very successful (30%). In the meantime, they have become handier whereby 90% of the attempts result in open oysters. Should you attempt to bike along the Wadden Sea dike, you will see just how successful they have become. But watch out for flat tires!