Abstract
Fish populations of water bodies of the lower Paraguay River at Formosa area (26° 10´S ‐ 58° 10´W) sampled during 1971 are studied. Qualitative and quantitative structure of fish communities, as well as dominance and occurrence, and size of fishes are analysed. Some limnological parameters, such as surface area, depth, and plant cover of the lagoons are included. Comparisons are made between the fish fauna present in these water bodies and those caught in other ones of similar characteristics located in the middle Paraná River.