Lanszki József - Ábrahám Levente (szerk.): Vadon élő vidrák Magyarországon - Natura Somogyiensis 14. (Kaposvár, 2009)

WILD LIVING OTTERS IN HUNGARY (SUMMARY)

Diet and fish choice of otters in fish wintering ponds in Hungary The diet composition and fish preference of piscivorous Eurasian otters were studied in two fish farm systems in Hungary using spraint analysis during two wintering periods. The primary food source of otters in both fish farms was fish (97-99% of biomass). The main fish prey was small-sized, below 100g in weight (96% in both areas), while fish prey above 500 g comprised only 0.1-0.4% of the diet. The bulk of the otters' diet consisted of less valued species, especially non-native Prussian carp (Carassius auratus gihelio). Consumption of commercial fish species ranged between 15% and 31% of the total diet. Otters preferred fish below 100g in weight (Ivlev's selectivity index, Ej=0.650.70), and showed a lesser preference for (or avoided) fish above 100 g in weight (Ej=0.37-1.00). With regard to species distribution, otters preferred small (< 100 g) grass carp (Ctenopharyngodon idella), zander (Sander lucioperca), pike (Esox lucius), Prussian carp, topmouth gudgeon (Pseudorashora parva), while they consumed common carp (Cyprinus carpio), the most important commercial species, proportionally to its abundance in the environment (Ej=-0.

18-0.29).