European Eel (Anguilla anguilla) stock size, anthropogenic mortality and silver eel escapement in the Netherlands 2006-2023

Samenvatting

Since the 1980s, the arrival of glass eel at the coast and the European eel stock have declined sharply. ICES (the International Council for Exploration of the Sea, www.ices.dk), which provides advice on the status and management of fish stocks at the request of the European Commission (EC), has therefore recommended the implementation of a recovery plan since the 1990s. As a result, in 2007 the EU introduced the ‘Council Regulation establishing measures for the recovery of the stock of European eel (EC 1100/2007)’. This regulation (the 'Eel Regulation') requires Member States to develop and implement a national eel management plan. The purpose of these eel management plans is described as follows (Article 2.4): ”The objective of each Eel Management Plan shall be to reduce anthropogenic mortalities so as to permit with high probability the escapement to the sea of at least 40% of the silver eel biomass relative to the best estimate of escapement that would have existed if no anthropogenic influences had impacted the stock. The Eel Management Plan shall be prepared with the purpose of achieving this objective in the long term.” - The analyses carried out for this report have once again shown that large assumptions have to be made to arrive at a biomass estimate of silver eels. The extent of the reprocessing (eel biomass in all Dutch waters) and the available (historical) data do not lend themselves to very accurate calculations. The stock indicator estimates should therefore be interpreted with caution due to the significant degree of uncertainty surrounding these estimates.