OBJECTIVES The general aim of proposed research project is to detect and quantify the impacts of new fish species on ecosystem functioning and to provide the most suitable adaptation strategies to change in ecosystem services. The major hypothesis is that invasion of new fish species will change the ecosystems currently dominated by generalist whitefish towards either benthivorous percid or alternatively planktivorous salmonid dominated ecosystems having major impacts on ecosystem functioning and services. Research objectives 1. To reveal the impacts of invasive species on food web structure and energy flows by comparing the lakes with only native fish species to lakes containing both native and invasive species. 2. To detect how the invasion of new species influences local catch in terms of species composition as well as its fatty acid, vitamin D and mercury levels by comparing the lakes with only native fish species with lakes having both native and invasive species. 3. To estimate the change in yearly supply of healthy (fatty acid, vitamin D) and harmful (mercury) substances for local people received from the lakes with only native fish species with lakes having both native and invasive species.