Common Dolphinfish

Appearance

Mahi-mahi have compressed bodies and a single long-based dorsal fin extending from the head almost to the tail. Mature males have prominent foreheads protruding well above the body proper. Females have a rounded head. Their caudal fins and anal fins are sharply concave. They are distinguished by dazzling colors: golden on the sides, and bright blues and greens on the sides and back. The pectoral fins of the mahi-mahi are iridescent blue. The flank is broad and golden.
Out of the water, the fish often change color, going though several hues before finally fading to a muted yellow-grey upon death.

Mahi-mahi can live up to five years, although they seldom exceed four. Females are usually smaller than males. Catches average 7 to 13 kilograms and a meter in length. They rarely exceed 15 kilograms, and mahi-mahi over 18 kilograms are exceptional. Mahi-mahi are among the fastest-growing of fish. They spawn in warm ocean currents throughout much of the year, and their young are commonly found in rafts of Sargassum weeds. Mahi-mahi are carnivorous, feeding on flying fish, crabs, squid, mackerel, and other forage fish. They have also been known to eat zooplankton and crustaceans.

Males and females are sexually mature in their first year, usually by 4–5 months old. Spawning can occur at body lengths of 20 cm. Females may spawn two to three times per year, and produce between 80,000 and 1,000,000 eggs per event. In waters averaging 28 °C/83 °F, mahi-mahi larvae are found year-round, with greater numbers detected in spring and fall.
Mahi-mahi fish are mostly found in the surface water. Their flesh is soft and oily, similar to sardines. The body is slightly slender and long, making them fast swimmers; they can swim as fast as 50 knots.

Habitat

Depending on how it is caught, mahi-mahi is classed differently by various sustainability rating systems:

⤷ The Monterey Bay Aquarium classifies mahi-mahi, when caught in the US Atlantic, as a Best Choice, the top of its three environmental impact categories. The Aquarium advises to avoid imported mahi-mahi harvested by long line but rates troll and pole-and-line caught as a Good Alternative.
⤷ The Natural Resources Defense Council classifies mahi-mahi as a "moderate mercury" fish or shellfish, and suggests eating six servings or fewer per month.
⤷ The Environmental Defense Fund classifies mahi-mahi caught by line/pole in the US as "Eco-Best" in its three-category system, but classifies all mahi-mahi caught by longline as only "Eco-OK" or "Eco-Worst" due to longline "high levels [of] bycatch, injuring or killing seabirds, sea turtles and sharks."

The mahi-mahi is also a common vector for ciguatera poisoning.

Food

Depending on how it is caught, mahi-mahi is classed differently by various sustainability rating systems:

⤷ The Monterey Bay Aquarium classifies mahi-mahi, when caught in the US Atlantic, as a Best Choice, the top of its three environmental impact categories. The Aquarium advises to avoid imported mahi-mahi harvested by long line but rates troll and pole-and-line caught as a Good Alternative.
⤷ The Natural Resources Defense Council classifies mahi-mahi as a "moderate mercury" fish or shellfish, and suggests eating six servings or fewer per month.
⤷ The Environmental Defense Fund classifies mahi-mahi caught by line/pole in the US as "Eco-Best" in its three-category system, but classifies all mahi-mahi caught by longline as only "Eco-OK" or "Eco-Worst" due to longline "high levels [of] bycatch, injuring or killing seabirds, sea turtles and sharks."

The mahi-mahi is also a common vector for ciguatera poisoning.