Rutilus rubilio, recently introduced into Sicily, is now widespread in many man‐made basins and watercourses of the island. We investigated a population living in a man‐made hypertrophie basin of southwest Sicily (Lake Arancio) in 1995. Sampling was monthly by a trawl and trammel net. Morphometric and meristic features were taken, and sagittal otoliths were extracted to assess age.R. rubiliorepresented the dominant species in the fish community of the man‐made basin. The population was characterized by a slower isometric growth, as related to age, than the population of South Italy.Rutilus rubiliobecame naturalised successfully and has contributed in altering the composition of the fish community described in 1977 by Faranda.