Effects of fish farming on macrophytes in temperate carp ponds

Anthropogenic impacts on carp pond environments have increased over the last 100–150 years in Central Europe. Present semi-intensive carp pond management combines natural food resources, supplementary feeding and additional intensification measures such as manuring, liming, and winter and summer drainage. Despite increased eutrophication and fish stock pressure, many carp ponds still serve as habitats for threatened biota, including macrophytes. Both the ecologically essential role of aquatic macrophytes and the impacts that reared fish may have on them have been repeatedly reported in the literature; however, information is scattered and there exists no multidisciplinary synthesis of knowledge of fish farming and plant interactions for European carp ponds. In this review, we show that macrophytes from different ecological groups have specific demands regarding optimal ecological conditions (e.g. pH and trophy level); hence, they can act as indicators of a water body’s ecological status. Nevertheless, the overall ecological ranges of many species (i.e. the limits enabling their survival) remain rather broad. Moreover, interactions between the different elements within carp pond ecosystems are complex and change rapidly, facilitating the co-existence of macrophytes with contradictory ecological demands. As the literature suggests, carp ponds may play a role in biodiversity protection that is just as important (or even more so) than that of natural wetlands. Sustainable, environmentally friendly carp pond management is undoubtedly the best means of preserving the unique natural and cultural value of these aquatic ecosystems for the future.