Otter Lutra lutra damage at farmed fisheries in southeastern Poland, II: exploitation of common carp Cyprinus carpio

I carried out a 2-year study on otter Lutra lutra dietary composition at a fish farm in southeastern Poland, where otters were perceived to inflict serious damage to common carp Cyprinus carpio stocks. The aim of my study was to determine the role of commercial fish in the diet of otters living in habitats comprising carp fisheries. Otter diet was examined by scat analysis. On an annual basis, carp dominated otter diet with 43% by weight. However, in terms of numbers, smaller wild species such as Prussian carp Carassius auratus gibelio (27%) and roach Rutilus rutilus (12%) were more abundant in the diet, whereas carp accounted for only 10%. The availability of farm cohorts of different age compared with frequencies of carp age classes recorded in spraints indicated otter preference of 1 over 2 carp. The exploitation of farmed stocks was most intense from autumn to early spring, unless the access to stocks was prevented by the presence of ice cover. In areas with carp farms, otters may rely on cultured stocks, especially during periods of food stress.