Mosquito larvae consumption in turbid waters: the role of the type of turbidity and the larval stage in native and invasive fish

Agricultural runoff and biological invasions alter native species interactions with implications for the management of pests. Here, we used live larvae of common house mosquito Culex pipiens to test the efficiencies of the invasive fish Gambusia holbrooki and the IUCN endangered fish Aphanius iberus to manage mosquitoes at three ecologically relevant concentrations of algae and clay. Both species reduced mosquito abundance in aquaria and outdoor mesocosms though A. iberus reduced it at a slower pace. However, G. holbrooki preferentially captured larger larvae at all fish sizes, whereas smaller individuals of A. iberus captured higher number of smaller larvae. Algal turbidity, but not clay, reduced the efficiency of both species, probably because of an adaptation to inorganic turbidity. Fish efficiency was not reduced in mesocosms where fish captured mosquito larvae interacting with natural invertebrate assemblages. Managers should maintain algal turbidity at < 10 FTU based on the visual detection threshold for both species. Our study shows that algal turbidity threatens the potential of waterbodies to naturally control mosquitoes and discusses why the faster foraging rates of alien species such as G. holbrooki should not be used to justify more introductions.