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Dutch oysters and consumer health

Imported oysters and consumer health

Annual Dutch oyster output

Storing oysters

Oysters and libido

Effects of fishing and cultivation on oyster population

Differences between gigas, bélon and fine de claire

Opening the oyster


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 monitoring 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 do not meet health standards, the area of origin is immediately closed until it again meets the criteria. The oyster production areas in the Netherlands generally meet the quality criteria year-round. In addition to quality control in the production areas, monitoring also takes place at the sites where the oyster ponds are located and at the 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 causes high mortality rates in Pacific oysters. Eating oysters infected with this virus poses no danger whatsoever to consumer health.

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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 authorities has implemented strict regulations concerning the purification installations and the traceability of imported oysters.

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Annual Dutch oyster output

Dutch oyster landings are subject to strong fluctuations. The Institute for Agricultural Economics publishes an annually updated overview of all Dutch oyster landings from the year 2001/02 onwards.

Before this period, the former Dutch Fisheries Board, published an annual overview of Dutch oyster landings. Landings between 1989/90 and 2000 are in the table below
(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


 
5.373
7.550
138
1.676
1.154
930
739

2.228
2.306
816
1.221


 
5.309
6.525
10.485
11.504
20.978
16.977
24.829

14.262
20.358
28.150
28.580


 
11.046
14.075
10.983
13.180
22.132
17.907
25.568

16.490
22.664
28.966
29.801


Source: Dutch Fish Product Board (Productschap Vis)

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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.

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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.

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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. 

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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.

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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.

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