Monitoring and advice on managing the eel population
Researchers of Wageningen Marine Research study trends, occurrence and behaviour of the European eel in Dutch lakes, rivers and streams. Market sampling also determines which sizes and ages are extracted by the fishing industry. The various samplings form the basis for (model) calculations, which are used to evaluate eel stocks in the Netherlands. The data are also supplied to ICES (International Council for the Exploration of the Sea), which provides international advice on the entire European stock every year.
Decline in eel stock
The stock of European eel is only a fraction of what it was before the 1980s. In the North Sea, the percentage of glass eel that arrives at the coast is about 0.6% (ICES advice 2021). In November 2021, ICES announced that the eel situation remains critical and, using the precautionary principle, advises that no more eels should be caught and that other mortalities caused by human activities should be stopped or minimised.
One of the causes of the decline is a reduction in the eel's habitat due to an increase in barriers, such as dikes, dams and hydroelectric power stations - in the Netherlands alone there are some 15,000 obstacles that make it difficult for the eel to migrate. Other causes of the decline in the European eel population are fishing, parasites, climate change, pollution of surface waters and predators.
Eels are a widespread species with a special life cycle. All European eels spawn in the Sargasso Sea, making the eel stock from North Africa to Norway a single stock. Eel management is therefore an international affair.
To enable the recovery of the population, the European Commission, by means of the Eel Regulation, has obliged Member States to draw up eel management plans, including a description of management measures. The Dutch Eel Management Plan includes protection measures such as the adjustment or removal of physical barriers, the release of glass eel, a restocking obligation for recreational fishers and a closed season (September to November) for eel fishing. Wageningen Marine Research is involved in the triennial evaluation of this Eel Management Plan.
- Long-term monitoring and data sets of eel stocks in the Netherlands and internationally, the recruitment of glass eel and the migration of glass eel and silver eel in Dutch waters.
- Contributions in advising ICES (WGEEL) on eel management in Europe
- Three-yearly EU evaluation of the Dutch eel management plan
- Research on dioxin residues in eels