vi Abstract Continental subspecies of the great cormorant (Phalacrocorax carbo sinensis) is the Czech Republic's most important fish-eating predator. It causes damage to production fish, as well as sport fishermen and even after its removal from the Czech list of endangered species in 2013, it did not disappear from the spotlight of both local fishermen and researchers. This thesis evaluates the qualitative and quantitative composition of the cormorant's diet during winter 2011/2012 at two selected locations: the Žehuň pond (Kolín district) and Berounka river in the natural reserve Zábělá near Pilsen. This work studies the main components of cormorant's diet in the selected locations and evaluates potential fluctuations and changes in its composition during winter. The study also conducted the analysis of the proportion of commercially harvested valuable fish in cormorant's diet and studied its diversity of the species spectrum. The resulting data for the two sites were compared with each other and with relevant literature. Regurgitated pellets analysis, as well as analysis of diagnostic bones and fish remains located at the sleeping roosts (night roosts) were used for the diet analysis. It was found that at both sites roach was the most caught fish, but from the point of view of total biomass, it was...