Latin name

Coryphaena hippurus

Other names

Dolphinfish, common dolphinfish, mahimahi, mahi mahi, dorado; Chinese: fei niau fu, ngau tau yue; French: coryphéne commune; Italian: lampuga; Japanese: shiira, toohyaku; Portuguese: doirado, dourado; Spanish: dorado, dorado com ún, lampuga.

Identification

The body is slender and streamlined, tapering sharply from head to tail. Large males, called bulls, have a high vertical forehead, while females have a rounded forehead. The anal fin has 25 to 31 soft rays and is long, occupying more than half the body length. The dorsal fin has 55 to 66 soft rays. The caudal fin is deeply forked. None of the fins have spines. The mouth has stripes of small teeth. The coloration is variable and cannot be accurately and simply described. Usually has a rich iridescent blue or blue-green color on the back, golden, bluish-gold or silvery-gold on the lower flanks and silvery-white or yellow on the belly. The flanks are studded with a mixture of dark and light spots, ranging from black or blue to gold. The dorsal fin is deep blue, and the anal fin is golden or silver. The other fins are typically golden yellow with blue edging. Dark vertical stripes sometimes appear when the fish attacks its prey. Describing the color of the dolphin is difficult because it is subject to sudden color changes that occur instantly, often when the fish are excited. However, when the fish is retrieved from the water, the colors fluctuate between blue, green, yellow. The bright colors that were visible when the fish was in the water quickly fade. After death, the fish usually turns uniformly yellow or silvery gray.

Distribution

The species is widespread in the epipelagic of tropical and subtropical waters of all oceans. It is known from Hawaii to the Tuamotu Islands. In the eastern part of the ocean, it is found in the waters of Oregon, California, and Peru. In the Indian Ocean, occurs throughout its northern and central parts. Occurs off the coast of Australia and South Africa. In the western Atlantic Ocean, it is distributed from Nova Scotia to Brazilian waters. Numerous in the Caribbean Sea and Gulf of Mexico. In the eastern part of the Atlantic Ocean is found from the Bay of Biscay to the mouth of the Congo River, also inhabits the Mediterranean Sea.

Habitat

The common dolphin is a warm-water pelagic fish that lives in the open ocean close to the surface, also found at depth. They sometimes inhabit coastal waters, in areas near piers, in the open ocean often concentrate around watercraft. Larvae and juveniles are found in coastal and near-island areas that are in the zone of warm currents.

Size

The average fish size ranges from 5 to 15 pounds, although it is not uncommon to catch fish as large as 50 pounds. The world record in tackle is considered an 87-pound specimen caught in Costa Rica in 1976. Dolphins grow quickly and do not live long. Few dolphins live longer than four years. Males grow larger than females and can grow to 60 pounds in as little as 2 years. They reach sexual maturity in their first year of life.

Life history and Behavior

The common dolphin is a prolific spawner, grows quickly. The spawning period starts mostly in spring or early summer and lasts several months in warmer waters. The dolphin reaches sexual maturity in the first year of life and produces large numbers of eggs. Dolphin often congregate in large numbers, sometimes by the thousands. They are almost always between the surface and 100 feet deep, and are also found on the surface or just below the surface. They are the most surface-oriented of all the big fish, feed mostly in daylight. Very popular among anglers. These fish are migratory. Dolphins in both hemispheres migrate away from the equator in the spring and summer, and toward the equator in the fall and winter.

Food and feeding habits

It is a predator with a fairly wide range of food. They swim in small flocks and shoals, intensively consuming forage fish. Flying fish and squid are the main food. The diet of small dolphins includes small fish and crustaceans that live in floating thickets. Dolphins are very aggressive and move very fast to catch food.

Reproduction

Reproduces year-round. It spawns in portions. A female hatches from 240,000 to 3 million eggs. The eggs are pelagic with a diameter of 1.28-1.62 mm, without excrescences; the yolk is granulated, there is a fat blob of a light yellow color. Embryonic development lasts 2-2.5 days. The length of unformed larvae after hatching is about 3.95 mm.

Interesting facts

The skin of the common dolphin is not just a passive covering, but a complex and dynamic structure that actively participates in controlling water flow and reducing drag during swimming. This conclusion is supported by modern research in hydrodynamics and biomimetics. Scientists have identified several key mechanisms by which this works:

The internal structure of the dolphin's skin is highly organized and differs significantly from the chaotic structure of terrestrial mammal skin. The orderly arrangement of dermal ridges, as well as collagen and elastin fibers in the blubber layer, create a complex, layered structure. This structure is a natural analogue of an anisotropic compliant wall — an engineering concept that has been shown to effectively reduce friction in the turbulent boundary layer. In essence, this "flexible" skin acts as a shock absorber, damping unwanted fluctuations in the water flow.

Research has shown that the microstructure of the skin (e.g., the density and orientation of the ridges) is not constant across the body. Its parameters, such as layer thickness (HEP, HDP, HSL) and ridge angle, correlate with local flow conditions — particularly with water velocity and pressure gradients, and not just with Reynolds number. This suggests that the skin structure is "tuned" to specific hydrodynamic conditions in different parts of the body (e.g., the head, torso, or dorsal fin), optimizing flow around the body.

The surface of the dolphin's skin is not perfectly smooth. It has small, orderly cutaneous ridges, which, importantly, are oriented transversely to the direction of body movement, rather than longitudinally as in sharks. These transverse ridges would seem to create additional resistance. However, recent discoveries indicate that these ridges are in constant microscopic motion, generating so-called longitudinal micro-ultrasonic waves (LMUW). This dynamic pulsation of the skin may turn pressure drag into a negative force, effectively creating thrust, which is a completely new and promising explanation for the so-called "Gray's paradox."

Interestingly, dolphin skin is not only hydrodynamically active but also plays an important role in the body's water balance. Studies have shown that dolphin skin has high permeability to water. This fact highlights that, in addition to other functions, the skin is an active participant in physiological processes, which likely affects the condition of the skin itself and consequently its hydrodynamic properties.

Thus, the skin of the common dolphin is not a passive covering, but a highly efficient adaptive system that combines a complex structure, the ability to adapt to flow, and even active microscopic movement, which collectively allow dolphins to achieve high speeds with minimal energy expenditure.