Otter returns to Mark Valley as water quality improves near Breda
For the second year running, otters have been detected in the Mark Valley south of Breda, signaling improved water quality and biodiversity. This discovery highlights the success of cross-border efforts to restore natural habitats and strengthen ecological connections.
| Key Data Point | Details |
|---|---|
| Species Detected | Otter (via eDNA) |
| Location | Bovenmark, Mark Valley South (near Belgian border) |
| Year of Detection | 2024 and 2025 |
| Research Method | eDNA analysis (environmental DNA) |
| Key Stakeholders | Brabantse Delta water authority, INBO, Municipality of Breda |
| Project Involved | Interreg ‘Otter over de grens’ |
| Objective | Improve ecological water quality and connect otter populations |
| Ecological Role | Predator, indicator of healthy fish populations, controls invasive species |
The Brabantse Delta water authority is responsible for managing water systems and improving ecological quality in the region. Its efforts, such as the Mark Valley redevelopment, aim to restore natural habitats and support biodiversity, with the otter serving as a key indicator of success. The authority collaborates with local and cross-border partners to achieve these goals.
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Otter appears to have found its way to the Mark Valley south of Breda
For the second year in a row, traces of the otter have been found in the Bovenmark in 2025. Researchers from the Institute for Nature and Forest Research (INBO) collected water samples on behalf of the Brabantse Delta water authority. As in 2024, otter eDNA was detected in these samples near the Belgian border.
Improved water quality
The renewed discovery of otter traces confirms, according to the water authority, the importance of continued efforts to improve ecological water quality. Following the redevelopment of Mark Valley South in 2024, the water authority is now working on plans for Mark Valley North. Improving ecological water quality is the main objective, alongside nature enhancement and a more natural layout that should contribute to a robust connection between the Flemish and Dutch otter populations.
Karin van den Berg, portfolio holder for Nature and Biodiversity at the Brabantse Delta water authority: “The fact that otter traces have been found again is encouraging for the water authority, water quality, and nature. I am pleased that through our management and projects such as the Mark Valley, we are working to improve ecological water quality and strengthen biodiversity. As a predator, the otter plays a key role in balancing aquatic nature. It is no coincidence that the otter is one of our ambassador species. It is important to continue working with our Flemish and Dutch partners to improve the living conditions for the otter.”
eDNA
eDNA (environmental DNA) is a method for detecting species without actually seeing or capturing them. Animals leave behind DNA through droppings, skin cells, blood, or mucus. By analyzing samples for the DNA of specific species, their presence can be confirmed. However, the research does not reveal how many otters there are or whether they permanently reside in the Bovenmark.
Peter Bakker, Alderman for Nature Development in Breda: “The discovery of otter traces in the Mark Valley shows that our efforts within the Interreg ‘Otter over de grens’ project are paying off. In Breda, we are gradually making the city more accessible to nature. From safe routes along the city moats to nature-inclusive developments in ’t Zoet and Gasthuisvelden. This way, we are building a continuous, quiet, and green connection through the city. This not only helps the otter; it also makes our urban rivers livelier and more biodiverse for everyone.”
‘Otter over de grens’
The results of the eDNA research are shared with the European Interreg project Otter over de grens. Under the motto ‘cross-border cooperation,’ the water authority is working with the Municipality of Breda, the Flemish Agency for Nature and Forest, INBO, and twelve other partners to expand and improve the otter’s habitat. By strengthening living conditions on both sides of the border, a better connection is created between populations in the Netherlands, Belgium, and surrounding regions.
As a predator, the otter plays a key role in healthy aquatic ecosystems. Its presence serves as an ecological indicator of the quality of fish populations. Additionally, the species helps reduce invasive exotics, such as the American crayfish.