Dorado

The Dorado is a scarce golden fish. Its name reflects its color, as "dorado" is Spanish for golden. With the Stringfish it is tied for the most profitable river fish.

This fish is diurnal, meaning you will only see it during the daylight, or, more specifically, 4am - 9pm.

Donating to the Museum
When in the museum, this fish appears in the middle tank and the right tank.

In Wild World
Upon donating a dorado to the museum, Blathers will comment:

"Hoo my! Congratulations are in order! You've finally caught one, eh wot? Did the mighty dorado put up a good scrum? You've passed the test! You're initiated into the secret club of fisher folk!"

In City Folk
Upon donating a dorado to the museum, Blathers will comment:

"My hoo, I never dreamed someone in this town would hook a dorado! It's a fish that lives up to the image of El Dorado it conjures... I could gaze upon it all day!"

In New Leaf
In New Leaf an information board in the aquarium will list information about this fish.

"Dorado means "golden" in Spanish. As the name would indicate, these fish are gold and have black dots. They look like salmon but are very toothy, carnivorous, and related to piranha. They're such ferocious fish that other fish regularly flee from hem, fearful of becoming a snack. Their ferocious natures and power make them a prize catch among anglers."

Further Information
Dorado is Spanish for golden, a suitable name for such a shining fish. In real life they are frequently confused with the Mahi-mahi, Coryphaeus hippurus (dolphin fish) also called the Dorado, which is the name of an oceanic fish that it is unrelated to and does not appear in Animal Crossing. The two real life species of "freshwater" dorado are Salminus maxillosus and Salminus hilarii. This fish can be found in the rivers of South America, most notably the Parana River of Argentina, and its tributaries, and it isn't as rare as Animal Crossing makes it out to be.