Argentina shore lines

What is happening in Argentina to cause this?
Dead fish downstream from the Parana River.
The Paraná River is a river in south-central South America, running through Brazil, Paraguay, and Argentina for some 4,880 kilometres. Among South American rivers, it is second in length only to the Amazon River. It merges with the Paraguay River and then farther downstream with the Uruguay River to form the Río de la Plata and empties into the Atlantic Ocean.