Nonnative fish introductions disrupt ecosystem processes and can drive native species to local extinction. Two of the most widespread, introduced species are the common carp (Cyprinus carpio) from Eurasia and the Nile tilapia (Oreochromis niloticus) from Africa. In North and South America, these introductions stem from aquaculture facilities, as well as historical introductions for recreational angling. An emergent field of ecological niche modeling provides robust predictions of the geographic potential of alien species to better understand their capacity to become established at broad scales. We used this modeling approach to produce spatially explicit predictions of the invasive potential of common carp and Nile tilapia in the Americas. Model predictions were tested using occurrence data for established populations in their native area and in the Americas. Results indicated that predictive power of niche models was high. Distributional potential of common carp in the Americas covers most temperate regions and high mountain tropical aquatic systems, whereas that of Nile tilapia is focused in the tropics and coast areas. The consequences of the potential establishment of these exotic species can be profound on native aquatic faunas, particularly on highly diverse regions such as the Amazon Basin and central Mexico.

The resuspension of sediment by waves or currents is a major cause of turbidity in many shallow waters. Here we show that bottom‐feeding fish greatly facilitate this process by reducing the erosion resistance of the sediment. We use a fish‐removal experiment from a large Dutch lake to show that the absence of fish makes sediment resistant to wind effects, and we use controlled lab experiments to demonstrate that the effect of fish can be explained by the characteristic hole‐punching behavior used in the search for food. Undisturbed sediment in the laboratory consolidated rapidly. The critical water velocity needed for resuspension roughly doubled in 2 weeks. However, the acquired erosion resistance could be virtually eliminated by holes corresponding to only 2% of the sediment area. An analysis of a model based on our experimental results suggested that benthivorous fish may prevent sediment consolidation that, in the absence of fish, would sufficiently stabilize the sediment during a quiet period to resist wave resuspension during subsequent windy periods. Our results imply that, even in exposed shallow lakes that are turbid because of wind resuspension, a temporary reduction of fish stock may work as "shock therapy"to restore an alternative stable clear‐water state.