Effects of Common Carp on Aquatic Ecosystems 80 Years after “Carp as a Dominant”: Ecological Insights for Fisheries Management

The introduction of fishes into habitats outside their native range may result in dramatic ecosystem alterations. Circumpolar introductions of common carp Cyprinus carpio commonly induce perturbations to shallow lakes, inducing a phase shift from clear to turbid water. Cahn (1929) Cahn, A. R. 1929. The effect of carp on a small lake: The carp as a dominant. Ecology, 10: 271–274. [Crossref] , [Google Scholar] first reported a phase shift following common carp introduction. Since then, ecologists have sought to understand ecosystem responses to common carp perturbation. We present a synthesis on how common carp can affect aquatic ecosystems through a middle-out framework due to their capability to alter bottom-up and top-down processes. Common carp affect bottom-up processes by modifying nutrient and turbidity concentrations and phytoplankton abundance and diversity through benthic foraging, whereas zooplankton and benthic invertebrates can be affected by top-down processes through predation and reduced foraging efficiency. Common carp also reduce aquatic macrophytes that may switch lakes from the clear to turbid water equilibrium. Restoration efforts seeking to return ecosystems to the clear water state have attempted to remove common carp populations through numerous methods with varying success. Restoration efforts should focus on entire ecosystems (humans, habitats, and biota) in conjunction with common carp reductions to achieve the greatest success at minimizing the effects of common carp and to return lakes to the clear water state.