The rivers at the triple border — the Iguazú meeting the Paraná — mean fresh fish on menus across town, and it is worth seeking out. Surubí (spotted catfish) is the most common, a firm white fish that takes well to grilling; dorado and pacu appear when the fishing has been good. Served grilled or in stews with local herbs, this is a genuine regional speciality that you will not encounter in Buenos Aires or Mendoza.
Look for fish restaurants near the waterfront and on Avenida Córdoba. The surubí a la parrilla — simply grilled with lemon — is the most reliable preparation and shows the fish off well.