Arapaima...

The arapaima is believed to be the largest freshwater fish in the
world. While it certainly grows to a massive 10 feet in length and
450 pounds in weight (3 metres / 200 kilograms), its maximum size
remains unknown - although a length of 14 feet (4.5 metres) has
been widely quoted.
With numbers greatly reduced by commercial fishing, it is now
officially classed as an endangered species. Large specimens are
therefore much rarer than they once were, and the exceptional
giants of yesteryear are less likely to exist.
Consequently the arapaima is only rarely caught by sport-fishermen.
Throughout most of the Amazon it is considered impossible to catch
on rod and line.