Ábrahám Levente (szerk.): Válogatott tanulmányok V. - Natura Somogyiensis 17. (Kaposvár, 2010)

LANSZKI, J., MÓROCZ, A. & CONROY, J. W. H.: A vidra (Lutra lutra) kora tavaszi táplálék-összetétele a Gemenci Tájegység (Duna-Dráva Nemzeti Park, Magyarország) természetes élőhelyein

LANSZKI, J., MÓROCZ, A. & CONROY, J. W. H.: DIET OF EURASIAN OTTERS 317 1: Taplósi Holt-Duna (abbreviated as TD, 45 ha), 2: Holt-Sió (or HS, 38 ha), 3: Hátfői kobolya (or HK,10 ha), 4: Decsi Kis-Holt-Duna (or DD, 11 ha), 5: Nyéki Holt-Duna (or ND, 17 ha), 6: Bátai Holt-Duna (or BD, 50 ha). These lakes and connecting wetlands support numerous hydrophilic macrophytes (such as Nymphaea alba, Trapa natans, Nymphoides peltata, Salvinia natans

), and are surrounded by reed-beds (.Phragmites communis) and a mosaic of different type of natural forests such as Leucojo aestivi-Salicetum albae (all six areas), Carduo crispi-Populaetum nigrae (BD, HK, HS), Senecioni-sarracenici-Populaetum albae (BD, HK, HS), Scillo vindobonensis-ulmetum (TD, DD, ND) and planted poplar and/or willow hybrids (BD, HK, HS, DD, ND) (IVANYI & LEHMAN 2002, S

TETÁK 2003). Unusually, in 2007, during the cold (January-April) period, the mean temperature was +7.8 °C, the lakes were not covered with ice and the duration of snow cover lasted only two days. During 2007, electrofishing took place on the Grébec-Duna (0.8 km north-east from the Decsi Kis-Holt-Duna) and Nyéki Holt-Duna. In both areas low fish numbers were recorded (Z. Sallai pers. comm.). The main species being giebel carp (Carassius auratus) (45.6%), bitterling (Rhodeus sericeus) (12.5%), roach (Rutilus rutilus) (11.0%), pumpkinseed (Lepomis gibbosus) (8.1%) and black bullhead (Ameiurus melas) (7.7%). On the Nyéki Holt-Duna, besides the dominant giebel carp (65.0%), black bullhead (15.0%), bleak (Alburnus alburnus) (10.0%), common carp (Cyprinus carpio) and rudd (Scardinius erythrophthalmus) (5.0-5.0%) were also caught. Sample collection and diet analysis To study the diet and feeding habits of the otter, individual spraints (faeces) samples were collected from all the areas in April 2007; corresponding to the cold (partially winter and early spring) period. Spraints were soaked in water and then washed through a 0.5 mm sieve and dried at room temperature. All recognisable prey remains were separated. These were then examined under a microscope and fish species identified based on the morphological differences of scales and bones, e.g. pharyngeal teeth, operculae, dentaries, maxillaries (e.g. BERINKEY 1966, KNOLLSEISEN 1996; and personal collection). Both amphibians and fish have single and paired bone structures around the head that allow an assessment of the minimum number of individuals in a spraint through the pairing of left and right sided bones of the same size. To avoid overestimating the importance of the given fish taxa (CARSS & NELSON 1998), different fish bones, combined with scale characters, were used to distinguish and identify fish species (and weight categories). The estimation of actual biomass consumed provides a more realistic measurement of the nutritive value of a prey, emphasizing the importance of larger prey. Weight category was recorded on the basis of comparative measurement of the available pharyngeal teeth, operculae, praeoperculae, maxillaries, vertebrae or other fish bones from the spraint and using a reference collection. Individual fish were divided into the following categories: < 100 g, 100-500 g, 500-1000 g and > 1000 g. The riverine habitat of the various fish species were based on observations by to SALLAI (2002a, 2002b) and LANSZKI and SALLAI (2006): reophilic (characteristically flow preferring), eurytopic (tolerant of both rivers and standing waters) and stagnophilic (characteristically preferring stagnant waters). The fish species were also categorised into native and non-native species according to SALLAI (2002). Other species preyed upon by otters were identified by microscope from