Dutch professional fishermen catch their fish mainly in the North Sea and the Atlantic Ocean. Much of this fish is exported. Mussels, oysters and cockles are caught in the waters of Zeeland and in the Wadden Sea. In the freshwater lakes such as the IJsselmeer (Lake IJssel) and the Markermeer professional fishermen catch eels, perch and pike perch.
Eel, European catfish and trout are the most important types of fish that are farmed in the Netherlands on a commercial scale. The eel nurseries work with young eels, known as glass eels, that must be caught. The numbers of European glass eels are a matter of concern, which may in the future produce problems not only for the eel fishery but also for the eel farms.
The possible accumulation of environmental pollutants in fish, molluscs and crustacea is largely determined by the quality of the water and the sediment under the water. For a variety of reasons the surface water, and thus the fish, may become polluted with diverse contaminants. Industrial waste water, for example, can contain diverse organic and inorganic substances.
In domestic waste water, cleaning chemicals and washing powders, along with bacteria, are the most important pollutants in this connection. A significant part of the excessive concentrations of phosphate and nitrate in the water can be attributed to agricultural sources. The same is true for the presence of traces of pesticides. The fisheries sector can generally exercise little influence on these sources of pollution.
The fish farming sector does have an influence on the use of veterinary drugs. By means of good record keeping and proper operating methods the sector can ensure that the level of traces of veterinary drugs in fish products is low or immeasurable. The Dutch Fish Farmers Association (Nederlandse Vereniging van Viskwekers, NeVeVi) has given extensive consideration to this problem in its research programme over the past year.