Frequently asked questions

Dutch oysters and consumer health

Imported oysters and consumer health

Effects of fishing and cultivation on oyster population

Differences between gigas, bélon and fine de claire

Dutch oysters and consumer health

Since oysters are usually consumed raw, bacteria may pose a health risk to consumers. Besides bacteria, toxic algae can cause health risks. Some people are allergic to shellfish proteins.

To protect consumer health, the Dutch government started a sanitary control programme as early as in 1906. The European Commission has introduced a number of directives in relation to the quality of shellfish production areas and the placing on the market of live bivalve molluscs. In the Netherlands, weekly samples are taken on the cultivation parcels and common grounds. If these samples are not of sufficient quality, the area of origin is immediately closed until it again meets the quality criteria. The oyster production areas in the Netherlands generally meet the quality criteria year-round. In addition to quality control in the production areas, regular sanitary check ups take place at the sites where the oyster ponds are located and traders' sites. Strict regulations are in use.

In 2010 the herpes virus was discovered in the Eastern Scheldt. The virus is also common in other European waters. It can cause high mortality rates in Pacific oysters. Eating oysters infected with this virus poses no danger whatsoever to consumer health

Imported oysters and consumer health

In the past, consumers have been affected by eating contaminated oysters that were imported from abroad. To prevent this from happening, the European Commission has made stricter directives concerning the placing on the market of live bivalve molluscs. In this context, the Dutch government has implemented strict regulations concerning the purification installations and the traceability of imported oysters.

Annual Dutch oyster output

Dutch oyster landings are subject to strong fluctuations. The oyster producers are obliged to return statements of their landings to the Dutch Fisheries Board. The table presents the landings (x 1,000 oysters) from 1989/90 onwards.

Landings of flat oysters (Ostrea edulis) and Pacific oysters (Crassostrea gigas) in the Netherlands (x 1,000 oysters) :

Season	Flat oysters (Ostrea edulis)	Pacific oesters (Crassostrea gigas)	Total
1989/90 1990/91 1991/92 1992/93 1993/94 1994/95 08/95-12/96 1997 1998 1999 2000 2001* 2002* 2003* 2004* 2005* 2006*	5.373 7.550 138 1.676 1.154 930 739 2.228 2.306 816 1.221 1.334 833 1.194 1.765 809 853	5.309 6.525 10.485 11.504 20.978 16.977 24.829 14.262 20.358 28.150 28.580 30.035 31.822 28.258 27.406 25.789 27.946	11.046 14.075 10.983 13.180 22.132 17.907 25.568 16.490 22.664 28.966 29.801 31.369 32.715 29.452 29.171 26.598 28.799

Source: Dutch Fish Product Board (Productschap Vis), *preliminary data

Storing oysters

Oysters are packed up in baskets. They have to be stored in a cool place. At a temperature between 3 and 7 degrees centigrade, they can be kept for a week without quality losses.

Tainted oysters give off an unpleasant smell and their shells stay open.

Oysters and libido

Oysters are renown as a sexual stimulant. Scientific proof is, however, lacking. How oysters got this 'claim to fame' will probably remain a mystery.

Effects of fishery and cultivation on the oyster population

Sometimes seed oysters from other production areas in Europe are used in the cultivation process. The outbreak of the oyster disease Bonamiasis in the Netherlands was caused by the import of contaminated French seed oysters. Furthermore, the relaying of imported shellfish may cause the introduction of dinoflagellates, i.e., harmful toxic algae. To prevent these externalities, measures have been taken at European and national level. These measures are strictly controlled.

Difference between gigas, bélon and fine de claire

Gigas (or Pacific oysters) and the fine de claire are both from the same oyster family (Crassostrea gigas). The bélon originates from the family of native oysters (Ostrea edulis). Flat (native) oysters have a regular round shape. Members of the gigas family have long and irregular shells. It is also more difficult to open gigas.

The fine de claire is cultivated in basins along the French Atlantic coast. The presence of an algae species in those basins causes the blue-ish colour of the oysters and is responsible for its soft flavour with an almost sweet aftertaste.

The bélon is a native oyster that originates from Riec-sur-Bélon in France, but is now extinct. Flat oysters are an indigenous species and are cultivated all over Europe. The Netherlands also has its own Zeeland flat oyster or bélon.

Opening the oyster

Wrap the oyster in a clean cloth, round half facing down. Clean shells when dirty. Make sure you have a proper knife with a blunt blade, preferably a special oyster knife.

Flat oyster: hold the oyster (wrapped in cloth) in such a way that the hinge joint is next to your thumb. Move the knife along the edge of the oyster towards the hinge. Cut the meat off the upper shell (flat shell). Remove grit carefully using the knife. Cut the meat off the round shell.

Pacific oyster: put the oyster (wrapped in cloth) on a hard surface and put the knife between the hinge joint. Make sure the knife points away from you. Once the hinge is broken, cut the meat off the lower shell. Remove grit carefully using the knife. Cut the meat off the round shell.