I think it's the local name for Mahi-mahi. When I've been to Costa Rica, we caught 2 of them and they tasted grilled very good. Mild, not too fishy and a medium-firm texture. Haven't eaten sushi from it yet.
Dorado has dry meat. Best is to cook it at parrilla. It is against the law to sell it at pescaderías.
You can try it at the end of the high way to Tigre, on the left you have a good fish cantina (good food at a no fancy place).
You cannot eat raw, it gets rotten too fast.
Surubi (giant catfish) is great but the meat has a lot of fat. This is not bad for health but you have to cook it at parrilla.
Pacu's meat is great (it is like a big piranha). The best is to cook it with chimichurri a la parrilla.
If you are in Rosario, go to parrilla Escauriza, they do the fishing, it is súper fresh and it is not expensive.