Status of the fish communities and need for management in the Po River Delta

The term “delta”, have used as a synonym for transitional water bodies, includes the terminal stretch of rivers, estuaries, deltas, fjords and lagoons, as defined by the EU WFD directive. Wetlands are sites of high biodiversity and productivity, with great ecological interest, functional richness and great exploitation of renuwable resources. Recently, these ecosystems have suffered a serious decline worldwide due to human disturbances. The Po River delta (Adriatic Sea, Italy) and the related coastal lagoons are not an exception. In the last twenty years, extensive phenomena of eutrophication and related dystrophic crises, introduction of alien species and the development of new fishing and aquaculture practices have further contributed to the breakdown of biological communities and, in particular, of fish ones. The aim of this study was to update the general status of the fish communities in the Po Delta of Emilia-Romagna, both in composition and trophic structure, and to identify the main problems of fisheries related to the physical evolution of the environment and the change in human activities. The results show that freshwater and transitional water suffered from different pressures: freshwater communities are affected by a progressive invasion of exotic species, which has intensified starting from more than 30 years ago. Whereas, fish communities in transitional water do not suffer of exotic fish invasions, but their overexploitation and play a central role in fish community changes. The cases of eels and the fishery of Comacchio are presented and analized as study cases.