THE DEPENDENCE OF FISH COMMUNITY STRUCTURE AND DYNAMICS ON FLOODPLAINAND RIPARIAN ECOTONE ZONE IN PARANA RIVER, BRAZIL

Flood intensity was a main factor determining access to the riparian/f loodplain ecotonal resources of the upper Parana River, Brazil, and in consequence determining yield of the dominant trophic groups, which a re fish feeding on flooded grasslands and on riparian fruits and leave s. Prey and predator density both declined in years of low floods, and predators did not recover until the next year of high flood, more slo wly than in the case prey fish, most probably due to differences in li fe cycle length. The life cycle of one of the most important species, Curimba (Prochilodus lineatus - Characidae) depends on access to the f loodplain lagoons and return to the reservoir after maturation for int ensive growth. The riparian/floodplain habitat complexity and connecti vity has great significance for fish community dynamics and fisheries yield, and may serve a reason to create a national park in the last fl oodplain section of the upper Parana River.