Tomasz Krepski

Analysis of benthic macroinvertebrate communities from the Lower sections of Large river in relation to different environmental factors

The aim of this study was to make a comparative analysis of macrozoobenthos composition at different sites at selected sections of lower the Odra River with relation to different physicochemical factors. The observations were made on the lower section of Odra River at five study sites: two of them were localized in the main channel, one in the left branch of river, another one in the channel carrying post-cooling water from Dolna Odra power plant, and the last one was in the channel connecting both branches of Odra River. At all sites, 26 taxa were found representing by: Bivalvia, Gastropoda, Oligochaeta, Hirudinea, Malacostraca and Insecta. The greatest biodiversity and the highest abundance of zoobenthos organisms were noted in the channel joining the two branches of the river, site 5, characterised by the lowest water flow rates and the densest coverage of the macrophytes at the bottom. Temperature was the sole parameter to be studied that affected the composition of benthic invertebrates. A clearly negative impact of temperature on the diversity of invertebrates was observed only in the channel with post-cooling water discharged from the power plant.

Weekly changes in prey availability for and the selective feeding of sea trout (Salmo trutta L.) larvae stocked in small forest streams

Abstract This study examined the availability of food and its selection by sea trout Salmo trutta L. fry in the first four weeks of life after yolk sac resorption. The food base and stomach contents of sea trout fry after release in the wild were determined. The study was performed in two small forest streams from April 25 to May 23, 2014. Macro-zoobenthos that comprised the food base for the fry were collected from the streams weekly using a bottom scraper. On the same day, the fry were captured with electrofishing gear. Analysis of the width of the benthic organisms in the food base and in the fish stomachs indicated the prey size range that the fish were feeding on. Further, the study showed that all food items found in both streams during the study weeks were also represented in the intensity of the fish: Cyclopoida, the larvae of Baetidae, Simuliidae and Nemouridae.