Lukáš Poledník, Kateřina Poledníková, Andreas Kranz, Aleš Toman
Lynx, n.s. (Praha)
Diet of the Eurasian otter was studied using the analysis of 2701 spraints collected along banks of 40 ponds in Českomoravská vrchovina (Bohemian-Moravian Highlands) in 2003–2004. Fish dominated the diet (80%, expressed as the relative number of individuals), with 19 different species identiﬁ ed. The proportion of ﬁ sh in the diet varied signiﬁ cantly at different ponds, ranging from 25% to 100%. Amphibians (frogs, toads and occasionally newts) made up the second most important prey group with 13%. Crayﬁ sh were only locally important, reaching 4% of prey consumed. Other prey groups such as insects, birds, mammals and reptiles occurred rather sporadically. The common carp was the most important ﬁ sh species in the diet (24%), reﬂ ecting the fact that the ponds are primarily used for its production. However, its proportion in the diet at ponds with stocked carp varied signiﬁ cantly from 2% to 91% of prey consumed. Other ﬁ sh species regularly found in the diet were perch (11%) and tench (9%). Roach, sunbleak, morroco, gudgeon, stone loach and grass carp were locally important. Other ﬁ sh species were taken rather occasionally. The diet varied among ponds concerning both the number of ﬁ sh species consumed and their proportion in the diet. Commercial ﬁ sh species made up 35% in the warm period and 42% in the cold period. When the diet composition was expressed in biomass values, the proportion of carp, and consequently of commercial ﬁ sh showed considerable differences compared to their relative abundance in the diet: 69% vs. 24% in the case of carp, and 70% vs. 35% in commercial ﬁ sh, respectively. Proportion of commercial ﬁ sh may be reduced signiﬁ cantly when alternative prey (non-commercial ﬁ sh species, frogs, crayﬁ sh) is available.