Veronesi R, Nicola Pandolfi, Alberto Alberani, R Bellini
Nature–protected coastal plain areas in the Po River Delta, Italy, are subjected to periodic flooding. Such phenomena create temporary water habitats conducive to the development of salt marsh mosquitoes, such as Aedes caspius (Pallas) and Aedes detritus (Haliday), which cause significant nuisance impacting the tourist industry. Mosquito control is therefore required, but conflict arises about the need to safeguard endangered bird species typically nesting in the wetlands. Despite the fact that adopted mosquito control methods are designed to cause as little disturbance as possible, authorities responsible for nature conservation require that the possible impact of larval control activities are further reduced. These concerns have served as an incentive to seek out alternative control strategies, such as the enhancement of the predatory action of fish species inhabiting the salt marsh biotopes. The most abundant of these species is the native Aphanius fasciatus (Valenciennes) (Cyprinodontiformes Cyprinodontidae). The access of fish to isolated pools and lowlands subjected to occasional flooding can be promoted by connecting them to major permanent water bodies via shallow ditches or runnels, which are dug by hand. The results of four years of observations and larval sampling in a salt marsh area of about 4 ha, located in the natural reserve of “Sacca del Bellocchio” where a system of runnels has been planned and constructed, suggest that runnelling can be an effective, long–lasting larval control method, favouring the predatory action of fish.