Josefina Mavrogeni¹, Zuzana Musilová², Kateřina Jandová¹, Reinhold Hanel³ and Petra Horká¹, (1)Charles University, Faculty of Science, Institute for Environmental Studies, Prague, Czech Republic, (2)Charles University, Faculty of Science, Department of Zoology, Prague, Czech Republic, (3)Johann Heinrich von Thünen Institute; Federal Research Institute for Rural Areas, Forestry and Fisheries, Institute of Fisheries Ecology, Bremerhaven, Germany