Marcin Brzeziński

Spring migration rates and community structure of amphibians breeding in an old and newly established midfield ponds

Abstract. n We studied the amphibian breeding migration into an old established (the beginning of the 1990s) pond and a new one (2007), using drift fences in 2008–2011. The two ponds were located at a distance of about 0.5 km from one another in a post-agricultural landscape in the Mazurian Lakeland, north-eastern Poland. We examined the community structure and migration rates of adults and juveniles. The amphibian breeding communities were similar in the two ponds in each year. The moor frog Rana arvalis was the most common species and comprised between 35 and 55 % of all adult amphibians migrating to both ponds. The new pond was colonized by adult amphibians in the first spring after its creation. In the second year, the amphibian migration rates doubled in the new pond and remained stable over the next two years. However, during the entire period of the study the old pond was a more attractive spawning site than the new pond, when measured by the number of migrating individuals of all recorded species. Despite some annual variation, there were no significant differences between the ponds in terms of the sex structure, mean body mass or migration timing of the predominant amphibian species. The most probable explanation for the observed differences in the rates of migration is breeding site fidelity.

Dam reservoir affects diet of otters inhabiting mountain river in SE Poland

Abstract. n The diet of otters was studied by the means of spraint analysis in the Bieszczady Mountains, in southeastern Poland. The study area extended over 25 km long stretch of the River San, about 1 km above Solina dam reservoir. Spraints were collected on seven 2 km long sections in 1993, and on three sections in 2010. In both study periods, otter spraints were collected in August, when the weather conditions were similar. The study revealed high contribution of mountain fish species such as Phoxinus phoxinus, Cottus spp., and Barbatula barbatula in otter diet. Diet composition along the River San showed little variation in 1993, except from the section closest to dam reservoir where it was characterised by the highest frequency of occurrence of perch Perca fluviatilis, cyprinids and amphibians. The share of perch in otter diet decreased, while that of noble crayfish Astacus astacus increased with the distance from Solina reservoir. Changes in otter diet between 1993–2010 were characterized by an increase of the consumption of perch and cyprinids on the one hand, and a decrease of the consumption of crayfish, on the other. Both spatial and temporal changes in otter diet reflected the effect of Solina reservoir on the river community and the availability of prey to otters. The results indicate the ongoing changes in fish community influenced by the construction of Solina reservoir.