The common name for the popular food fish Mahi Mahi frequently causes confusion, leading many people to ask if it is a dolphin. The truth is straightforward: the Mahi Mahi is a species of fish, completely unrelated to the intelligent, air-breathing marine mammals known as dolphins. Understanding the biology and the history behind the names clarifies this distinction.
Mahi Mahi: A Bony Fish of the Open Ocean
The Mahi Mahi, scientifically classified as Coryphaena hippurus, is a bony fish belonging to the class Actinopterygii (ray-finned fishes). It is a highly pelagic species, living near the surface of the open ocean in tropical and subtropical waters across the globe. This fish is recognizable by its compressed, long body and a single, distinctive dorsal fin that runs nearly the entire length of its back.
A striking feature of the Mahi Mahi is its vibrant, iridescent coloration, including blues, greens, and golden-yellows that fade rapidly after death. Mature males, often called “bulls,” develop a distinct, blunt, bony forehead crest (sexual dimorphism), while females retain a more rounded head profile. Mahi Mahi are known for their rapid growth, commonly reaching lengths of about one meter, though some individuals grow to over two meters.
The Origin of the Confusing Name
The primary source of confusion is that the Mahi Mahi has historically been called the “Dolphin Fish,” especially by Atlantic sailors and fishermen. This name was likely given because the fish frequently swims and leaps near the surface of the water, reminiscent of the marine mammal. The use of the single word “dolphin” to refer to the fish became common, causing the present-day mix-up.
To avoid consumer confusion and the mistaken belief that people were eating a protected marine mammal, the seafood industry adopted the Hawaiian name “Mahi Mahi.” The Hawaiian term means “strong-strong” or “very strong,” referencing the fish’s powerful swimming ability. Another common name, particularly in Spanish-speaking regions, is “Dorado,” meaning “golden” in reference to its coloration.
Biological Distinctions Between Fish and Mammal
The fundamental biological differences between the Mahi Mahi (fish) and the dolphin (mammal) are rooted in their respective classes, Actinopterygii and Mammalia. One significant distinction is respiration: the Mahi Mahi uses gills to extract dissolved oxygen from the water, allowing it to remain submerged indefinitely. Conversely, the dolphin is an air-breathing mammal that must surface regularly to inhale oxygen through a blowhole.
Another separation lies in thermoregulation. The Mahi Mahi is poikilothermic, meaning its body temperature fluctuates with the surrounding water temperature. The dolphin, like all mammals, is homeothermic, maintaining a constant, warm body temperature independent of its environment. Reproduction also varies dramatically: the Mahi Mahi reproduces by spawning eggs, which are fertilized externally. Dolphins, however, give live birth to their young and nurse them with mammary glands.