Contribución al conocimiento del zooplancton del Alto Paraná

Resumen

Knowledge of the zooplanktonic community of the Paraná River—as well as that of other large South American rivers—is rather poor and fragmentary.

The results of studies carried out along a 250 km stretch of the Upper Paraná River between the localities of Corpus and Itá Ibaté (which includes the area of the future Yacyretá reservoir) are presented in this paper. Samples were obtained monthly over a period of 22 months from 1976 to 1978 by filtering 100 liters of water through special sieves with a mesh size of 63 µm, at four sampling stations located at the deepest points of the river sections.

The zooplanktonic community in these waters is composed mainly of a considerable number of species (38 Rotifera, 12 Cladocera, and 8 Copepoda), exhibiting a very varied structure and population density ranging between 2 and 60 individuals per liter. The community structure is strongly influenced by variations in river discharge and the consequent dilutive effect of the waters.