Mahi Mahi: Not a Dolphin, and Nothing Like the One on Your Plate
Mahi mahi is a fish, not a dolphin, and the gold you see in a cooler is the ghost of what it looked like alive. Colour, speed, bulls and cows, and the bait ball.
Mahi mahi in the wild
By William Drumm, underwater photographer and ocean ambassador
The first thing you notice is the colour, and the second thing you notice is that it will not hold still. A mahi in the middle of a hunt flickers through electric blue, green and gold like something malfunctioning, and it changes faster than you can react to it.
The second thing you notice is that everything else in the water is also here. Sea lions, striped marlin, seabirds coming in from above. A bait ball is not a mahi event. It is an event that mahi attend, at speed, and they are usually the most beautiful thing in it.
No, It Is Not a Dolphin
Let us deal with this immediately, because it is the single most searched thing about this animal.
Mahi mahi is a fish. Coryphaena hippurus. It is not related to dolphins in any way. Dolphins are mammals.
The confusion is entirely a naming problem. The old English name for this fish is dolphinfish, which is a fine name right up until it appears on a menu, at which point people understandably recoil. So the restaurant industry adopted the Hawaiian name, and mahi mahi is what stuck.
Three names, one fish:
- Mahi mahi. Hawaiian. It means, roughly, strong strong.
- Dorado. Spanish. It means golden. It is also the best of the three names.
- Dolphinfish. English, accurate, and commercially catastrophic.
The Colour Is the Whole Story
Mahi have pigment cells they actively control, and a hunting fish uses them. The colour is not a paint job. It is a display, running in real time, and it flickers and pulses as the animal accelerates and turns. It is thought to serve both as a hunting signal, disorienting prey, and as communication with other mahi working the same bait.
When a mahi dies, the control stops. Within minutes the blue and gold drain out and what is left is a dull yellow grey. Almost everyone who has ever seen a mahi has seen a dead one, on a dock or in a cooler, which means almost everyone has seen the wrong thing. The photographs on this page are what the animal actually looks like.
It is the best possible argument for photographing fish alive.
Built for Speed
A mahi is a blade. Deep, narrow, laterally compressed, with a huge forked tail and essentially no wasted mass anywhere on it. Burst speeds are commonly cited at close to 50 mph, which puts them in the same conversation as the animals they hunt alongside.
Watch one work a bait ball and you understand the design. They do not stalk. They arrive.
Bulls and Cows
Male mahi, called bulls, grow a steep, tall, blunt forehead that is unmistakable once you know to look for it. Females, cows, keep a rounded, sloping head. Bulls also grow considerably larger.
Typical fish run 15 to 30 pounds. A big bull can pass 5 feet and 50 pounds, and the all tackle record sits in the high 80s.
Live Fast, Die Young
This is the part that reframes everything else about them.
Mahi mahi live four to five years. That is it. In exchange they grow at a rate that is close to unbelievable for a fish of that size, putting on well over an inch a week in good conditions, reaching breeding age within months, and hitting adult size inside a year.
Everything about the animal follows from that. The speed, the appetite, the colour, the urgency. A mahi has almost no time and it behaves like it knows.
It also has a strange consequence at the fish counter. Because they grow and breed so fast, mahi populations absorb fishing pressure far better than slow growing species do, and line caught mahi is one of the more defensible things you can order. How it was caught matters much more than what it is: longlines take a great deal of bycatch with them.
The Bait Ball
This is where I photograph them, and it is the best show in the ocean.
A bait ball forms when predators push a school of small fish up against the surface, which is the only wall available in open water. Once the ball is up there, everything comes. Sea lions drive through it from below. Striped marlin come in from the side, lit up and using their bills. Seabirds hit it from above, punching down through the surface. And the mahi come fast through the middle of it, gold and electric, taking fish on the move.
None of them are cooperating, exactly. They are all exploiting the same failure of the same school at the same time, and the result is a genuinely coordinated looking spectacle that nobody is coordinating.
Photographing Mahi
They are hard, and it is not the speed that makes them hard. It is that everything worth photographing about a mahi happens inside a bait ball, and a bait ball is a churn of bubbles, sea lions, marlin, scales and whitewater in which nothing holds still for a full second.
Shoot fast, shoot wide, shoot a lot. Expose for the fish and let the water go where it wants. And get the colour, because the colour is the entire reason to be there, and a mahi that is lit properly for a fraction of a second is one of the most spectacular animals in the sea.
If you want the rest of the bait ball cast, there is the striped marlin, and more on the craft in how to become an underwater photographer. Prints are in the shop, and a portion of every sale supports marine conservation.
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Is mahi mahi a dolphin?
No. Mahi mahi is a fish, Coryphaena hippurus. It has nothing to do with dolphins, which are mammals. The confusion comes from its other English name, dolphinfish, and it is exactly why the Hawaiian name mahi mahi took over on menus: nobody wanted to think they were eating Flipper.
What is the difference between mahi mahi, dorado and dolphinfish?
They are three names for the same fish. Mahi mahi is Hawaiian and means strong strong. Dorado is Spanish and means golden. Dolphinfish is the old English name and the reason for a century of confusion. The fish does not care.
Why does mahi mahi change colour?
Because it can. Mahi have specialised pigment cells that they control actively, and a hunting or excited fish flickers through electric blue, green and gold in real time. It is thought to be both a hunting display and a way of signalling to other mahi. When the fish dies the control goes, and the colour drains to a dull yellow grey within minutes. The gold on a fish in a cooler is the ghost of what it looked like alive.
How fast can a mahi mahi swim?
Very. Mahi are among the faster fish in the ocean, with burst speeds commonly cited at close to 50 mph. They are built for it: a deep, narrow, blade shaped body, a huge forked tail and almost no wasted mass.
How long do mahi mahi live?
Four to five years, and rarely more. They are one of the shortest lived large fish in the ocean, and they compensate by growing at an extraordinary rate and breeding almost as soon as they are able.
How fast do mahi mahi grow?
Faster than almost any other fish. Mahi can put on well over an inch a week in the right conditions, reach breeding age in a matter of months, and be a fully grown adult within a year. Live fast, die young, in the most literal sense available in biology.
How big do mahi mahi get?
Commonly 15 to 30 pounds. A big bull can exceed 5 feet and pass 50 pounds, and the all tackle record is in the high 80s. Males, called bulls, are noticeably larger than females and grow the tall blunt forehead.
What is the difference between a bull and a cow mahi?
The forehead. Males develop a steep, tall, almost vertical blunt head as they mature, which is unmistakable once you have seen it. Females keep a rounded, sloping head. Bulls also grow considerably larger.
What do mahi mahi eat?
Flying fish, small schooling fish such as sardines and anchovies, squid, crustaceans, and the juveniles of almost anything that shelters under floating debris. They hunt near the surface, often in packs, and they drive bait into tight balls and take it apart from the outside.
Where do mahi mahi live?
Warm surface water worldwide, in the open ocean rather than on reefs. They congregate around anything floating: weed lines, sargassum mats, logs, debris. If you find a floating object in blue water, look under it.
Is mahi mahi sustainable to eat?
Comparatively, yes, and this is one of the rare cases where the fast, short life is good news. Mahi grow so fast and breed so early that populations can absorb fishing pressure in a way slow growing species cannot. Line caught mahi is generally among the better choices at the counter. Longline caught mahi carries a bycatch problem, so how it was caught matters more than what it is.
Do mahi mahi hunt in groups?
Yes. They work bait balls cooperatively, and they frequently do it alongside completely different species. Sea lions, striped marlin and seabirds will all work the same bait ball at the same time, from different angles, and the mahi come in fast through the middle of it.
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