Italian aquaculture and the diffusion of alien species: costs and benefits

The aim of this review is to clarify the relation between Italian aquaculture and the introduction on alien species in Italy. In Italy, the most common aquatic alien species are rainbow trout and Manila clam, and they represent main economic product of Italian aquaculture. Wels catfish and red clawed crayfish have been voluntarily or involuntarily introduced for aquaculture scope, and they are now the most invasive alien aquatic species. Other alien naturalized species, as some salmonid species, are important economic resources in north Italy for inland professional fishery and are considered worthwhile of conservation. Thus, aquaculture is directly or indirectly responsible of the introduction of several alien species in Italy, but its effect on alien species diffusion is peculiar, as few successfully farmed species have become rapidly common. Until now, conventional aquaculture has played main role in the diffusion of alien species in Italy, while ornamental aquaculture will be the main source of alien introductions in the future.