Distribution and population structure and dynamics of the red swamp crayfish Procambarus clarkii (Girard, 1852) in the eastern Po Valley and its Delta (northeastern Italy).

Procambarus clarkii is among the “100 of the worst” invasive aliens in Europe. The geographic distribution and population dynamics of the species were studied for the first time in inland waters in the eastern Po Valley and its Delta, an area for which such information was absent. The geographic distribution of P. clarkii was assessed by sampling, in summer 2017, 12 geographically distant water bodies representative of an area of 3,000 km2. Population dynamics was studied from 2017 to 2018, in a canal running through the town of Ferrara. Growth and longevity were estimated using the von Bertalanffy growth function. Procambarus clarkii was found in 100% of the water bodies sampled, indicating that red swamp crayfish has now completely colonized the eastern Po Valley, where interconnected field irrigation systems have allowed crayfish to spread almost everywhere. From the analysis of the polymodal frequency distributions, 5–6 growth cohorts were observed, each cohort corresponding to 1 year of age. Sex-ratio was 1:1, and no appreciable between-sex differences were found in growth patterns of crayfish population, except for the asymptotic length for which females approach higher values. Differences in life history parameters with other Italian populations may be due to latitudinal and different ecological conditions at our study sites.