The Fish Ecology Research Group studies various aspects of the biology and ecology of aquatic organisms (primarily fish) and their interactions with the aquatic environment, as well as aspects of fisheries and water management. The team’s research activities are focused on the evaluation of sampling methods, the study of natural fish reproduction and the ecological requirements of fish in different aquatic environments. We also use fish as a model group to answer general questions on the biology of invasions, especially the predictability of invasions and their impacts. We also address issues related to fish hybridisation and physiological investments in reproduction, immunity and metabolism. In relation to fish parasites, we study changes in parasite communities related to the introduction of non-native species, environmental fragmentation and pollution of aquatic ecosystems. The knowledge gained from this multidisciplinary approach contributes to a better understanding of biotic interactions within fish communities, such as competition, predation, hybridisation and parasitism, as well as environmental factors that affect such communities. The outputs of our applied research are used in the protection of species and the environment, optimisation of fisheries management for the needs of recreational fishing, water management interventions and biomanipulation and revitalisation measures.