Moreover, gigantic submerged boulders, sunken trees, sandbars, undercut banks, and rocky points attract schools of sábalo. Argentina exports sábalo by the ton, but netting them is banned on the Upper Paraná, protecting this critical link in the food chain. As schools of sábalo move up and down the river, the dorado follow. Every so often, we witness a dorado suddenly ambush one near the surface; the violent attacks look and sound as if a cinder block has been dropped into the water. Once, we even spot a group of dorado corral their prey in the middle of the river before blitzing them like bluefish.