Measures for migratory fish, 2018

The construction of dams and pumping stations means that fish migrating from the sea or the major rivers are only able to reach a part of the streams and polder water areas. Fish passages help them reach some rivers and streams, with many more fish passages to be built in the coming years.

Continued poor accessibility for migratory fish

Migration between different water bodies is an important part of the life cycle of many species of fish. There are well-known examples of fish that migrate from the sea to small streams, but fish also migrate between large and small rivers, polder water and drainage basins. Obstacles such as dams, hydro turbines and pumping stations are a serious hindrance to such migration. There are currently many obstacles that hinder proper migration, so that only a part of the major rivers and a few streams are accessible to migratory fish.
Although the major rivers can be reached through the IJsselmeer and the Nieuwe Waterweg, the dams in the Afsluitdijk (IJsselmeer) present the first obstacle. The Haringvliet sluice gate forms part of an important migration route, as it is the main discharge channel for the Rhine. However, so long the decision to open the Haringvliet (kierbesluit) is not implemented, this will remain a major obstacle. The Rhine and the Meuse rivers have been fully accessible to migratory fish since 2007, thanks to the construction of fish passages at the large dams. Fish passages also make the IJssel river in the province of Overijssel accessible to fish. However, there are still thousands of dams in other inland water bodies, only a few of which can be negotiated using a fish passage. This means that only a few streams can be reached from the sea or the IJsselmeer: the Hunze (Groningen), the Eem (Utrecht and Gelderland) and the Mark (Noord-Brabant, near Breda).
Although fish passages have been constructed to enable upstream migration, downstream migration can still be a problem, for example in the Meuse. Migratory young salmon (smolt) and eel travel with the main flow and therefore through hydro turbines and dams, which kills many of them.

Policy objectives

The Benelux decision (M2009) states that anadromous and catadromous migratory fish must be free to migrate in all river basins. Eel, Anguilla Anguilla , salmon, Salmo salar, sea trout, Salmo trutta, and flounder, Platichthys flesus are mentioned in particular. The new Benelux decision includes a prioritisation map, part of which must be in place by 2015, and part by 2021, with all obstacles to be removed by 2027. At the 13th Conference of Rhine Ministers in 2001, the Programme on Sustainable Development of the Rhine was adopted. This includes the objective to improve migration routes for migratory fish.
The eel needs to migrate between the sea, brackish water and large and small rivers, ditches and lakes. It is important that the eel is able to reach ditches and drainage basins. The European Eel Regulation (European Union, 2007) was introduced with the aim that 40?% of adult eels are able to return to sea to spawn. Many measures need to be implemented to achieve this, to improve migration and to reduce deaths in hydro turbines.

WFD policy

The Water Framework Directive sets ecological objectives for surface waters, including fish stock objectives. Improving fish migration is one of the conditions for achieving these objectives. These objectives are to be achieved by 2015, or 2027 in the case of derogation. Implementation of the WFD is expected to result in migratory fish that are found in flowing water being able to reach many water bodies by 2027.


Technical explanation

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Reference of this webpage

CBS, PBL, RIVM, WUR (2024). Measures for migratory fish, 2018 (indicator 1350, version 09,

) Statistics Netherlands (CBS), The Hague; PBL Netherlands Environmental Assessment Agency, The Hague; RIVM National Institute for Public Health and the Environment, Bilthoven; and Wageningen University and Research, Wageningen.