This Coryphaena "showing a helmet" hippurus "horse tail" shows us that dorado means "gilded" in Spanish. According to one source, the mahi converts about 90% of its food into body weight, and can reach a length of 6.75 feet (and weigh almost 90lbs).
Apparently, they can reach 28 inches in six months and maintain a fast growth rate for the duration of their short lives. A really old dolphinfish might live to be 5 years old, but "current wisdom is that they live for a maximum of 4 years".
On a side note, I am truly baffled at how many people I hear ask "What's that fish that looks like a dolphin?". I know of no dolphin that has a blunt forehead and tapered body like the Mahi mahi. Their shape does remind me of a Sperm whale, though.
Wherever they are common, dolphinfish are also a major commercial fish. In many locations around the world, dolphinfish are attracted to bundles of bamboo or cork planks, then encercled with nets. (Examples are the Shiira-zuke fishery of Japan, the Kannizzali fishery of Malta and the Matas fishery of the Balearic Island).
(from Probably More Than You Want To Know About The Fishes Of The Pacific Coast)
Besides being delicious, mahi mahis put up a great fight if you hook them, oftentimes jumping out of the water and "spitting the hook". Apparently, they're not that bright. One of my old roommates, Brian, used to tell me of how he caught them by improvising an inside-out Fritos bag as a lure.
Though mahis will flash different colors when excited, they generally don't maintain this coloration for a long time. Hormones cause these color changes, which you will generally see when they are feeding, mating, or excited.
The color flashes of an excited dolphin fish are truly wonderful, but are short-lived like fireworks. When someone brings one of these home from a fishing trip, they usually mention how colorful they remember the fish being when it was brought on deck, and how colorless it looks after it dies.
