Latin name

Thunnus albacares

Other names

Allison tuna, albacore, autumn albacore, yellowfinned albacore; French: albacore, thon à nageoires jaunes; Hawaiian: ahi, ahimalai-lena; Italian: albacore, tonno albacora; Japanese: kihada, kiwade, kiwada maguro; Portuguese: alba-cora, atum amarello; Spanish: atún de aleta amarilla, atún de Allison, rabil.

Identification

This is probably the most colorful of all tuna. The back is blue-black, turning to silver on the lower flanks and belly. From each eye to the tail runs a golden yellow or shimmering blue stripe, although it is not always visible. All fins and plumage are golden yellow, although some large specimens may have elongated dorsal and anal fins that are silver with yellow edging. The fins have black edges. On the belly can often be seen up to 20 vertical rows of whitish spots. Many large yellowfin fish become particularly conspicuous because they grow very long second dorsal and anal fins. In general, the body shape is streamlined and more slender than that of bluefin or bigeye tuna. The eyes and head are relatively small. Characterized by elongated pectoral fins, elongated second dorsal and anal fins, which in some large specimens may reach more than half of the back to the base of the tail. In small specimens weighing less than 60 pounds, and in some large specimens, this may not be an accurate distinguishing factor. The pectoral fins in adults reach as far as the beginning of the second dorsal fin, but never extend beyond the second dorsal fin to the fins. Yellowfin can be distinguished by the black margins on their fins. The yellowfin has 25 to 35 gill wings on the first arch and has an air bladder. The tail lacks a white trailing edge.

Distribution

Epipelagic and mesopelagic fish of open waters of tropical and subtropical regions of the World Ocean. Occurs at water temperatures of 18-31°С. Widely distributed in tropical and subtropical seas of the World Ocean, where it occurs between 40-45°N and 35-40°S.

Habitat

This species is found worldwide in deep, warm, temperate ocean waters. It is a pelagic and seasonally migratory species, known to come fairly close to shore where there are warm currents. The largest yellowfin has been found in the Revillagigedo Islands off the coast of Baja California, Mexico.

Size

Yellowfins are usually caught under 100 pounds, but can grow up to 400 pounds. Their maximum length is 75 inches, and the world record for all-tackle fishing is held by a Mexican fish weighing 388 pounds 12 ounces. The age limit is 8–9 years with a length of 190-200 cm. At the end of the first year of life, length to 60 cm, at the end of the second year - 105 cm, in subsequent years growth slows slightly. They become sexually mature at a length of at least 110 cm and a weight of 10 kg at the end of the second or beginning of the third year of life.

Life history and Behavior

Yellowfins fish are quite numerous in tropical waters. Young fish are known to form large schools near the surface. Adults live in fairly deep water, but also live near the surface, and anglers catch them close to the surface. They often mingle with other species, especially skipjack and bigeye tuna. Yellowfins reach sexual maturity when they are about 40 inches long and spawn throughout the year in their main distribution areas, peaking during the summer months.

Food and feeding habits

The food spectrum is wide. The diet depends largely on local abundance and includes flying fish, other small fish, squid, and crustaceans.

Reproduction

Spawning occurs in the surface layers of water in the spring and summer of the respective hemispheres at temperatures not lower than 24 °C (often 27-30 °C). In the process of moving away from the equator, the spawning time is reduced and is usually confined to the warmer periods of the year. It does not form mass spawning aggregations. Absolute individual fecundity is from 1 to 30 million eggs, depending on the size of fish. The size of mature oocytes varies from 0.9 to 1.4 mm. Yellowfin tuna spawn in batches. In one spawning season, females may spawn 2–3 batches of eggs.

Interesting facts

Yellowfin tuna have specialized structures called finlets. These are small, non-retractable fins arranged in rows along the rear part of the body, in front of the caudal fin. They play an important role in controlling water flow, making swimming more efficient.

Research shows that finlets perform several hydrodynamic functions:

Analysis of the 'wake' from the finlets has shown that they create a special structure of vortex tubes and redirect cross-flowing water. This effectively 'smoothes out' the eddies that arise from body movement.

By interacting with each other, the finlets help reduce overall water resistance by about 21.5% compared to if they worked individually.

The finlets themselves perform oscillating up-and-down movements (diving and tilting). This allows the fish to reduce the power it expends on their movement by 20.8%. Moreover, the forces they create help the caudal fin move with greater amplitude, improving thrust.

It is worth noting that some studies have shown that at normal cruising speed, these finlets do not have a critical effect. However, they are believed to provide an advantage at high speed, as well as during rapid accelerations and maneuvers.

Thus, the finlets of the yellowfin tuna are not passive growths but an active hydrodynamic mechanism that helps one of the fastest fish in the ocean to efficiently manage water flow around its body.