Project information (English)

Restoring migration possibilities for 8 Annex II species in the Roer

Objectives

In the Molentak branch of the Roer near the ECI plant in Roermond and the near the dam in the Roertak there is a fish migration barrier. At these two spots there is an unbridgeable difference in level for fish. These barriers already existed as far back as 1290 when the hydraulic works in the Roer (dams and watermills) were constructed to make use of the waterpower of the fast-flowing river. As a result of these interventions, it is impossible for fish to run up either the Roertak or Molentak branch from the Maas. This means that, for numerous fish species, the large habitat, foraging and breeding areas of the Roer and its many large tributaries that lie behind are inaccessible. The breeding area constitutes a major link in the ecology of the anadromous and reophilic species (living in salt water, breeding in fresh water). The crucial character of the above-mentioned barriers in the estuary areas of the Roer is reinforced by the fact that these are the only barriers in the Dutch part of the Roer.

As early as the 1980s, as an initial action within the framework of the elimination of the fish migration barriers in the Roer Delta, a green overfall was built into the Hambeek (the third branch of the Roer in its lower reaches), which also fulfils the function of a fish migration facility. This fish migration facility was constructed in accordance with the insight available at the time. Due to improved insight it has been established that this facility (fish ladder) is not functioning adequately and needs modifying.

The following objectives can therefore be formulated:

General objective:
The objective of the project is to make it again possible for various species of fish to run up the Roer Delta so species such as the Atlantic salmon (Salmo salar) and other Annex II species namely asp (Aspius Aspius), bullhead (Cottus gobio), river lamprey (Lampetra fluviatilis), brook lamprey (Lampetra planeri), sea lamprey (Petromyzon marinus), bitterling (Rhodeus sericeus amarus), weatherfish (Misgurnis fossilis) can again access the upper reaches of the Roer, where they can spawn.

Project objective:
To install fish migration facilities in the Roer Delta, for example constructing a fish ladder and modifying the green overfall to help realise the general objective.

Actions and means involved

A study is currently being carried out into the exact location and precise fish migration facilities: (location and type) in the Roertak and Molentak branches of the Roer. The results of this research indicate the need for a fish ladder in the Roertak near to the current dam.

The green overfall (Hambeek) will also be modified to allow migrating species to pass.

Expected results

A major breeding area and habitat will be reopened for the fish species in question. The effects of this opening up lie in making suitable habitats again available in the mid and upper reaches of the Roer and its various tributaries. Even more significant is the opening up of the upstream breeding grounds for (anadromous and reophilic) fish species. These fish species can now progress through the total life cycle between salt water and freshwater.

The efforts being made by the national government in the Maas system are being concentrated on the optimisation of the passage from the North Sea to the entire Dutch section of the Maas and the efforts being made in Germany to breed a Roer stock salmon and sea trout can now be linked. After all, the barrier in the middle of the system between the North Sea and the upper reaches of the Roer will be eliminated.

The construction of the fish migration facilities will enable the populations of various species to recolonise the area and use the Roer as a core area from where, through population growth, other areas can also be colonised.