Abstract
The diet of Great Cormorant (Phalacrocorax carbo) was studied by means of (1) examining regurgitated pellets, individual fish bones and fish remains collected from below the roosting trees and by (2) analysis of stomach contents of shot birds at five localities in the Vltava River basin. Using diagnostic bones (maxillare, dentale, intermaxillare, praeoperculare, operculare, ossa pharyngea) a total of 3,039 fish of 25 species (including one hybrid) and 6 families (Cyprinidae, Percidae, Esocidae, Salmonidae, Cottidae, Anguillidae) were identified in the diet.
The sizes of fish prey were reconstructed using linear regression equations between measured dimension of the diagnostic bone and fish total length (LT). From the dominant species (86,2% of the diet), Roach (Rutilus rutilus) were taken in the length range 5-38 cm LT, European Perch (Perca fluviatilis) in the length range 6-37 cm LT, Bleak (Alburnus alburnus) in the length range 5-20 cm LT and European Chub (Squalius cephalus) in the length range 7-35 cm LT.
The largest fish taken by the Great Cormorants was 46 cm European Eel (Anguilla anguilla) and 41 cm Zander (Sander lucioperca), the heaviest fish was 755 g Roach and 734 g European Perch. Species with low value for anglers or fishermen as Roach, Common Bream, Bleak, European Chub, European Perch and Ruffe represented 67.0-98.1% of the diet of Great Cormorants on individual localities.