Dutch Afsluitdijk gets highway for endangered fish species

The Afsluitdijk protects the Netherlands against water but also forms an obstacle for many species of fish that are in danger of dying out as a result. By creating a very long meandering river right through the Afsluitdijk, an important link in the centuries-old fishing route will be restored. We call this a fish migration river.

When designing the Afsluitdijk, engineer Lely had not taken into account how the closure of the former Zuiderzee would affect the flora and fauna. That was not so important in those days.

Thanks to the express lane for the now endangered fish, they will soon be able to swim freely back and forth between the Wadden Sea and the IJsselmeer. A strong example of water board engineering innovation from the Netherlands, as this fish migration river is the first in the world.

Why is a Migration River in the Afsluitdijk necessary?

The Afsluitdijk now makes it virtually impossible for migrating fish to swim back and forth between the Wadden Sea and the IJsselmeer.

Countless fish are waiting in the Wadden Sea in front of the sluices. They smell the fresh water, want to go there with all their might, but are usually unable to withstand the strong current. This is one of the main reasons why the migratory fish stock is so incredibly low and the need for a solution so high.

When will the migration river be ready?

In 2020, the construction of this new nature link started immediately west of the sluice gates at Kornwerderzand. The river should be ready by 2023. It is the first artificial tidal river at the boundary of fresh and salt water in the world to be constructed. The Fish Migration River is thus a globally unique innovation that offers a safe and nature-friendly solution to a growing ecological problem.

Which fish will use the fish migration river

The fish migration river will ensure that fish can swim from salt to fresh water again. Migratory fish such as salmon, flounder and eel need both types of water to reproduce and grow. The Vismigratie river also contributes to healthy water, the recovery of the diversity of plant and animal species in the area and offers opportunities for eco-recreation.

Fish will have no trouble finding the fish migration river. They follow the smell of the fresh or salty water. Strong swimmers like shad, sea lamprey, flounder, sea trout and salmon swim independently to the other side of the dike. Weaker swimmers such as glass eel, smelt, stickleback and other young fish can let themselves be carried by the currents, as they flow into the Wadden Sea at high tide and back towards the IJsselmeer at low tide. Ideal for the smaller fish to hitch a ride on.

The water of the ‘river’ follows the tides of the Wadden Sea and has different flow velocities. Because salt and fresh water meet in the fish migration river, the fish can gradually get used to the transition during their journey. The many bends and the length of the river also prevent too much salt water ending up in the IJsselmeer.

How does this fish migration river work

To allow migratory fish to swim back and forth between the Wadden Sea and the IJsselmeer, just making a random hole in the Afsluitdijk is not enough. Moreover, there is also such a thing as water safety and the IJsselmeer is an important freshwater supply.

Years of thought went into determining the best design for all species of migratory fish. It resulted in the fishmigration river: a globally unique design.

The construction of a fish connection starts with the question of the best location. Millions of fish are already waiting in front of the sluices at Kornwerderzand at certain times of the year. They are attracted by the smell of fresh water that is spewed out here in millions of litres at a time. These are also the sparse moments when the waiting fish can attempt to reach the IJsselmeer.

Most fish species are unable to withstand that strong current. Impregnable barriers such as the Afsluitdijk are one of the main reasons why the stock of migratory fish is worryingly low. This is not only the case in the Netherlands, but throughout Europe it is a common problem.

Fish migration hotspot for eco-tourism

The Vismigratie river will also become a new starting point for experiencing the Wadden Sea World Heritage Site. This starts with a visit to the Afsluitdijk Wadden Centre. A free interactive exhibition is on display here. You can book and experience (sailing) excursions and lectures in and around the centre.