Free fishpassage: how does it work?

Thanks to the length of the Fish Migration River Afsluitdijk, fish can gradually transit from fresh- to salt water or vice versa. They will dwell in the area for a while, after which they will migrate further towards their breeding areas in- and outside of the IJsselmeer (IJssel lake). During their journey from the Wadden Sea to the IJsselmeer, the fish will get the extra push in the right direction thanks to the incoming tide.

Hitching a ride with the tides

The Fish Migration River Afsluitdijk begins to flow when the ebb tide flows, so when the water level in the Wadden Sea is low. The fresh water from the IJsselmeer flows into the Wadden Sea and forms a stream, which will attract various types of migratory fish anxious to enter freshwater. As the tide  rises, the river comes to a standstill. After which, when the tide falls, it will continue its flow towards the opposite side: a keen example of eco-engineering, which makes the Fish Migration River Afsluitdijk into a one-of-a-kind construction.

Strong and weak swimmers

Strong swimmers like salmon and seatrout are able to swim against freshwater streams. They can reach the freshwaters of the IJsselmeer on their own. But flounder, young eels, smelt and spined stickleback are weaker swimmers. They allow themselves to be carried along by the flood tide, hitching a ride in order to reach the IJsselmeer. In this way, the Fish Migration River Afsluitdijk will offer all migratory fish 24-hour migration options throughout the year.


Safety guaranteed

In case of emergencies, the Fish Migration River Afsluitdijk can be closed off on both sides. This, together with the length of the river and the tidal flow, will ensure that no saltwater can enter the IJsselmeer. That is a prerequisite, as the fresh water behind the dyke serves as an important source of drinking water for millions of people. The safety function of the Afsluitdijk also remains intact. The closing of the Fish Migration River Afsluitdijk meets the highest standards of the so-called primary embankment.

Want to know more? Watch this animation clip