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Angling clubs speed up natural fish colonisation of gravel pit lakes

Artificially created gravel pit lakes are often managed by angling clubs. The use of such lakes is subject to fishing rights, which come with an obligation to preserve wildlife: for example, the holder of the fishing right is required to preserve and maintain fish stocks at a level appropriate to the size and type of lake. But do fishing clubs take this responsibility seriously at artificial gravel pit lakes? This question was investigated in the context of IGB’s BAGGERSEE project in cooperation with the Angling Association of Lower Saxony and other research and practitioner partners. The researchers compared managed and unmanaged natural lakes as well as managed and unmanaged gravel pit lakes in Lower Saxony and Brandenburg. They found that lakes managed by anglers host similar fish species to unmanaged natural lakes. In contrast, gravel pit lakes that are not managed by anglers are at a young stage of development, have less species richness, and in some cases contain fish species that are not typically found in such freshwaters.

Perch are commonly found in unmanaged natural lakes. The fish also populates natural lakes and gravel pit lakes managed for recreational fisheries. | © Sven Matern

IGB’s fisheries biologist and lead author Sven Matern assessed the findings as follows: “Anglers speed up the colonisation time of gravel pit lakes by introducing native fish typically found in lakes, helping to create a near-natural fish community. In unmanaged gravel pit lakes, the establishment of fish species is more sporadic and appears to take longer. What is more, unusual captures in unmanaged gravel pit lakes, such as the common rudd, lead us to assume that fish are unfortunately being released illegally, e.g. from garden ponds.”

However, there could be a disadvantage to this accelerated method of fish colonisation. Professor Robert Arlinghaus, lead investigator of the study at IGB, explained: “The lakes that were managed by angling clubs or other bodies were very similar in terms of their fish community composition. From a nature conservation perspective, however, it may also make sense to have lakes at various stages of development and with different levels of species richness. To give an example: first colonisers such as sticklebacks benefit from the absence of predatory fish like perch. Amphibians are also sensitive to predatory pressure from fish. However, pools and drainable ponds are more suitable for amphibian conservation than gravel pit lakes, which do not remain completely fish-free for long.”

For their study, the researchers investigated a total of 178,000 fish from 50 gravel pit lakes, the majority of which were in Lower Saxony, and 16 natural lakes in Brandenburg.

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Robert Arlinghaus

Research Group Leader
Research group
Integrative Recreational Fisheries Management

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