Fish get private stream, otherwise they get lost

Fish that swim in the Limburg Maas reproduce in the Geleenbeek. To get there, they have to swim through the Oude Maas. It turns out that fish have trouble finding the entrance to the Oude Maas and get lost along the way, says Rijkswaterstaat. This is because the entrance to the Oude Maas is located at two large former gravel extraction lakes. There is very little current in the Molenplas and Biltplas.