Interactions between freshwater fisheries and birds

Long existing conflicts between fishermen and nature conservationists about the relative impact of human and avian exploitation of fish stocks seem to be based on poor scientific data. In this symposium fisheries ecologists and ornithologists combined their efforts to provide an overview of the current knowledge and to define the type of data that are needed for proper management of aquatic ecosystems. It was agreed that there is a need for a multidisciplinary approach, since changes in a fish population, caused either by man or birds, often cascade through the food web and organisms at any trophic level may react unexpectedly by adaptations in morphology, life history or behaviour. New sophisticated techniques like radio tracking and stable isotope analysis offer possibilities for the necessary detailed diet studies. It was noticed that a concentration of the research on lakes and rivers has underused the possibilities for experimental work in fish ponds and floodplains. However, experiments in such environments have now been started and their suitability for measurements solving the conflicts between fishermen and conservationists has been recognized. Future symposia should include comparable problems from the marine environment. Together we should provide the scientific base necessary to realize two objectives for aquatic ecosystems from Rio 1992: preservation of biodiversity and sustainable use.