To preserve ecosystem services of tropical reservoirs that provide food and income for local populations, it is necessary to monitor fish population temporal dynamics, stock, and yield fishing. The aim of this review is to provide information to who monitor fish populations in tropical reservoirs. The topics, investigative methods, observation scaling, and metrics used in publications since 1960's were inventoried. Temporal and spatial variations in fish population and fish production were the primary topics. Since 2000, studies on trophic structures and fish biological parameters have appeared. Experimental fishing with gillnets has been the technique most often used, but others include hydroacoustics for fish stock assessments and modeling to characterize trophic structures. Annual and seasonal scaling approaches dominated, as well as longitudinal/transversal gradient sampling, which permitted the characterization of fish colonization processes and the detection of halieutic resource overexploitation. For modeling approaches, the entire reservoir was considered. The calculated metrics varied depending on the investigation method. Species richness, number of individuals, and biomass per unit effort were the most common metrics for the different topics. Trophic level, effectiveness, and consumption rate were specific to trophic structure. To monitor reservoir fish populations, it is necessary to have an eco-systemic approach.