The HIDROVIA Project: Should We Be Concerned for Fish Resources?

HIDROVIA is a waterway project that, if completed, will require dredging and deepening of select reaches along the 3400 km De la Plata River basin. Fish diversity in the basin is great and dominated by detritivorous and bottom feeders. Large-sized, migratory species support valuable subsistence, commercial, and sport fisheries. In the upper Paraguay, dredging and anticipated increases in navigation traffic will severely impact shore-line habitats and likely affect fish fauna and mobilize shoreline sediments. In the middle and lower Paraguay Rivers and in the Parana River, dredging should not affect upstream fish migrations and therefore we anticipate only minor effects on the fishery. Dredging and sediment disposal will not release significant levels of contaminants because sediments are dominated by medium and fine sands. However in De la Plata River, dominance of silt and clay elevates concentrations of contaminants that may be released by dredging thus increasing bioaccumulation in bottom-feeding fishes and benthic organisms. These effects could be more severe in estuarine spawning habitats used by several eurihaline fish species.