The influence of cormorant (Phalacrocorax carbo sinensis) on the domestic fish fauna in Styria

Diploma thesis at the Karl-Franzens-University Graz In the course of cormoran monitoring, the cormorant situation in the core area of Gesäuse National Park was also investigated in the winter half-year 2006/07 by the Gesäuse National Park at certain sections of the Enns, Palten and Salza. The sleeping place in Großreifling (EN01) north of the National Park has been permanently occupied since the winter 2000/01 and also had an average population of 17 individuals in 2006/07. Questionable was another sleeping tree on the Enns in the Ardning area, but no indication of a cormorant could be found within the investigation period. The cormorant, a very adaptable bird and skilful hunter always stirs up the flowing waters of Austria. Many fishermen and ecologists are concerned about the stock of domestic fish fauna, especially the ashes (Thymallus thymallus). So also in the area of the Enns, Palten and Salza in Upper Austria. Here, however, the expert opinions differ on the extent to which the cormorant actually has an influence on the low fish stocks. In order to gain a better insight into the increase in winter guests, the data from 06/07 were also compared with the previous years. Finally, data from other registered sleeping places at the affected rivers throughout Styria were also used to maintain general trends in the migration behaviour of birds.