01846naa a2200265 a 450000100080000000500110000800800410001910000190006024501310007926000090021052011070021965000090132665000170133565000150135265000100136765000160137765300210139365300220141465300230143665300200145970000190147970000190149870000170151777300460153417898332017-04-03       1969    bl ---       0--  u    #d1 aBONETTO, A. A.  aCiclos hidrologicos del rio Parana y las poblaciones de peces contenidas en las cuencas temporarias de su valle de inundacion.  c1969  aThe hydrological regime of the Parana River is characterized by an annual cycle of high waters that reaches its maximum in summer, following a low flow period with minimum values in August and September. During the flood the middle Parana River overflows its valley the lenitic water lodies within the islands. When this happerns fish migrate between lenitic and lotic enviroments. At the same time the shallow water bodies (dried up during the last low watter period) receive important fingerling schools and large quantities of fishes of different species and sizes. When the water level lows the fish populations contained in lenitic environments may die by the great ecological modifications of its habitat and frequently by complete drying up of the ponds. This paper deals with the most outstanding characteristics of these phenomena during 1968, based on the study of several temporary water bodies in the middle Parana River Valley. Quantitative and qualitative data about fish populations are given, as well as their variations and the losses originated by the annual water level fluctuations.  afish  aParana River  apopulation  aPeixe  aPopulação  aBacia temporaria  aCiclo hidrologico  aHydrological cycle  aTemporary basin1 aYUAN, E. C. de1 aPIGNALBERI, C.1 aOLIVEROS, O.  tPhysisgv.29, n.78, p.213-223, oct. 1969.