Fish are good indicators of long-term changes of fluvial ecosystems therefore, assessment of fish assemblages is frequently used in evaluation of the ecological status of surface waters, especially since the implementation of the EU Water Framework Directive. Long-term changes of fish fauna and old-time abundance of fish populations in the Danube can be documented by historical data of fisheries. Direct detection of long-term changes of fish populations in large rivers is a difficult task due to large-scale temporal and spatial variability of fish distribution. The present study provides a review of river fish sampling methods, with special attention to approaches based on electrofishing. Our goal is to develop a standard monitoring method in large rivers to get more reliable and consistent data for description of long-term changes of fish populations.