Oyster, Pacific

In februari 2013 the Dutch oysterfishery in the Grevelingen and the Oosterschelde received MSC-certification. Despite the fact it is aquaculture, the MSC standard for sustainably caught fish was still applicable. That is because it is a form of aquaculture in which almost the whole process takes place in the wild and in a natural, uncontrolled manner.

The Dutch oyster fishery has received the MSC certificate after an independent team of scientists had established that the fishery and cultivation are carried out in such a controlled manner that there is no overfishing and that undesirable effects on life in and around the sea are limited to an absolute minimum.

The indigenous European flat oyster fishery and farming was doing very badly in Europe in the 60’s, due to overfishing and the oyster disease. Following this, the Pacific oyster was introduced in many places as an alternative for the oyster farmers. The Pacific oyster developed to a pest in almost all of north-west Europe, and outcompeted the indigenous shellfish at many places. With the introduction of the oysters, also other exotic animals and diseases were introduced.

The farming of oysters is done with several methods. Oyster larvae are farmed in hatcheries or caught in the water with specialised collectors. The oysters are often not farmed directly on the seabed. In the intertidal the oysters are often farmed in meshed bags on frames. At places that are always under water the oysters are farmed in crates or on ropes that hang in the water on floaters. These methods cause little disturbance to the environment. Oysters filter their food (algae) from the water and therefore do not need extra food. The Netherlands is one of the few countries where the oysters on the bottom are farmed on reserved oyster plots. This not only causes extra disturbance of the seabed, the oysters are also more vulnerable to diseases and predators.

There is nothing more to do about the invasion of the Pacific oyster. We can however prevent that diseases, parasites and other exotic animals can spread more by strict supervision and the restriction of transport of oysters between different areas. The European oyster culture is managed well, but often takes place in vulnerable areas.