Original paper

Fish preference of the Eurasian otter (Lutra lutra) on an abandoned fish pond and the role of fish sampling methods

Bauer-Haáz, Éva A.; Ferincz, Árpád; Szegvári, Zoltán; Széles, Gabriella L.; Lanszki, József

Abstract

The role of small (< 10 ha) ponds in biodiversity conservation has been recently highlighted. As a top predator, the Eurasian otter (Lutra lutra) may have a powerful effect on the biodiversity and ecological functionality of small ponds, regardless of their purpose (e.g. aquaculture, angling or conservation). Our study sought to analyze the feeding habits of otter in a near-natural system (Csombárdi pond, SW Hungary). From December 2010 to November 2011, the annual composition of otter diet was assessed by the analysis of spraint samples (n = 483). Fish abundance was assessed from spring to autumn by electrofishing and fyke nets. Throughout the study period, the main food source of the otter was fish (73.5–84.9% of occurrences), while amphibians represented a secondary resource. Otters behaved as opportunistic hunters, preying primarily on the most abundant fish species and size classes and conforming to seasonal variation in fish availability. Otter preferences in relation to fish habitat zones (shorezone or littoral, metaphyton, pelagic, benthic) and origin (native, non-native) differed according to the sampling method used to assess fish availability, suggesting that the sampling method chosen may distort the assessment of prey preference by otters. Two-thirds of fish eaten consisted of non-native species. Results may be useful for the conservation of otters, near-natural ponds, and associated native fish communities.

Keywords

conservationdietelectrofishingfeeding habitsfish selectionfyke nethungarylutra lutranon-native fishopportunism