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 identiﬁed. The proportion of ﬁsh in the diet varied signiﬁcantly at different ponds, ranging from 25% to 100%. Amphibians (frogs, toads and occasionally newts) made up the second most important prey group with 13%. Crayﬁsh 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 ﬁsh species in the diet (24%), reﬂecting the fact that the ponds are primarily used for its production. However, its proportion in the diet at ponds with stocked carp varied signiﬁcantly from 2% to 91% of prey consumed. Other ﬁsh 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 ﬁsh species were taken rather occasionally. The diet varied among ponds concerning both the number of ﬁsh species consumed and their proportion in the diet. Commercial ﬁsh 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 ﬁsh 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 ﬁsh, respectively. Proportion of commercial ﬁsh may be reduced signiﬁcantly when alternative prey (non-commercial ﬁsh species, frogs, crayﬁsh) is available.