Diet composition of otter Lutra lutra was quantified by analysis of 2 048 s
praints collected at half-month intervals concurrently with a one year cult
ure cycle of carp Cyprinus carpio in a fish pond area (S.E. Poland) and com
pared with data on farm stocks. Presence of cultured fish affected the diet
composition, carp being the single most important food. The estimated biom
ass proportion of carp in spraints varied monthly between 15.7 % in June an
d 78.0 % in March. Carp abundance changes could not explain the seasonal va
riation in predation pressure. The factors responsible for the seasonal shi
fts in the use of resources are discussed.