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Diverse habitats are required for river fish biodiversity restoration


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Floodplains should include a variety of fish habitats to restore river fish biodiversity. This is apparent from a large-scale study by Wageningen University & Research (WUR) in collaboration with Rijkswaterstaat, published in Science of the total environment (BUMP). In addition, the extent to which the restored floodplain is connected to the river determines its success as a nursery.

Between 2017 and 2020, Ph.D. candidate Twan Stoffers investigated the species richness and abundance of typical river fish in 46 restored floodplains along the major rivers in the Netherlands. “Floodplains are spawning and nursery grounds for river fish,” explains Stoffers. “As a result, optimizing these tree nurseries is crucial for the recovery of biodiversity in our rivers. The degree of connection with the river determines whether a floodplain is successful as a nursery. When a floodplain is connected all year round, you see high biodiversity and many fish.”

Habitat Mosaic

Another important feature of restored floodplains for the restoration of biodiversity is the presence of a wide variety of fish habitats. This can range from standing water with aquatic plants and overhanging willows to oxygen-rich fast-flowing water with cobblestones and boulders. River fish species have different demands on the environment in which they grow. The highest species diversity, up to 22 unique species per floodplain, occurs in places with a mosaic of habitats.

In contrast, such a diverse habitat is less favorable for some struggling species in Dutch rivers, such as the rhinoceros, dace and barbel. “These species need a very specific nursery habitat, which consists of shallow, flowing water with a coarse bottom,” says Stoffers. “They will be comfortable if these habitat features are present.”

With this large-scale evaluation, the researchers found that natural restoration along major rivers is undoubtedly beneficial to the river fishing community, but there are still areas of concern. The researchers found that many floodplains lose their connection to the river, especially at lower water levels later in the growing season. “This can form a bottleneck in the growth process,” explains associate professor Leo Nagelkerke. “This connection has to be in place when the young fish are big and strong enough to migrate to the river. Otherwise you’ll be undoing all your hard work to restore these nurseries.”

Restoring Fish Farms

Large floodplain rivers, in their natural form, continuously generate a variety of different habitats, for example through flooding. These habitats also disappear over time because they silt up or dry out. This dynamic environment is ideal for the growth of a wide variety of juvenile (reophilic) river fish.

Our rivers are now regulated for safety and navigation and this dynamic landscape has largely disappeared. This could explain why the populations of these animals remain so small. Therefore, it is necessary to establish and maintain different types of nurseries to allow specialized and critical river fish to recover.

The freshwater pearl mussel favors the native salmonfish populations of its home river

More information:
T. Stoffers et al, Restoring freshwater fish biodiversity in floodplain rivers requires connectivity and heterogeneity of habitats at multiple spatial scales, Science of the total environment (2022). DOI: 10.1016/j.scitotenv.2022.156509

Provided by Wageningen University

Quote: Different Habitats Needed for Restoring River Fish Biodiversity (June 2022, June 23) Retrieved June 24, 2022 from https://phys.org/news/2022-06-diverse-habitats-required-river-fish. html

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