The form and structure of fish otoliths are species specific. The validity of using otoliths found in pellets to determine the number, size and weight of fish consumed was tested on cormorants. They were fed with fishes of known number, size and weight; pellets were recovered after 24 hours. Sandsmelt(Atherina boyeri),striped mullet(Mugil cephalus),sole(Solea vulgaris)and eel(Anguilla anguilla)were used. It was found that it is possible to estimate the size and weight of prey consumed by birds from size or weight of the otoliths recovered from pellets.