Anders Nilsson has broad research interests in aquatic ecology, spanning e.g. fish migration, predator-prey and host-parasite interactions, behavioural ecology, phenotypic plasticity, population genetics, and fisheries management, in freshwater as well as marine systems, in numerous international research consortia. The fish migration research focuses on ecological and evolutionary causes and consequences of partial migration in freshwater fish. Partial migration, when only a portion of the individuals in a population migrates, is evaluated in light of a tradeoff between growth opportunity and predator avoidance that shifts between lake and stream habitats over seasons, causing migration patterns that differ between individual phenotypes and circumstances. Nilsson combines such ecological and evolutionary research and understanding with restoration incentives and fish passage development, towards win-win solutions for hydropower and fish.