No differences between littoral fish community structure of smallnatural and gravel pit lakes in the northern German lowlands

Habitat loss has been identified as a major contributor to declining freshwater biodiversity, resulting in a high threat level among European fishes. Non-natural ecosystems such as pit lakes may compensate habitat loss by providing new habitat for aquatic organisms. We compared the structure of the littoral fish communities of 18 natural and 19 gravel pit lakes located in the northern German lowlands to evaluate whether artificial lakes managed by angling clubs host similar communities as typically observed in natural lakes. The fish community structure was analyzed between the lake types and along gradients of lake morphometry, productivity and littoral complexity. Although the gravel pit lakes differed in morphology (characterized by steeper littoral slopes and less structured littoral habitat), differences in fish community structure between the natural and gravel pit lakes were weak and mainly related to differences in the abundance of the dominant species perch, roach and rudd. Both lake types had similar species richness, community diversity and hosted several small-bodied and endangered species. To conclude, fish communities characteristic of small natural lakes may serve as reference for the development of gravel pit lakes. Moreover, our study reveals that recreational-fisheries management of gravel pit lakes does not result in artificial communities that deviate strongly from the communities present in natural lakes. Therefore, nature conservation and fisheries management goals can be reconciled in relation to fish in small artificial lakes managed by angling clubs.