The yellowfin tuna was first described by Bonnaterre in 1788, when it was named Scomber albacares. The fish appeared under a variety of names before Ginsburg first used the combination Thunnus albacares in 1953. The genus name Thunnus is derived from the Greek "thynnos" meaning tunna. Many other names have been used to refer this tuna including Scomber albacorus, Thynnus argentivittatus, Scomber sloanei, Thynnus albacora, Thynnus macropterus, Thunnus argentivittatus, Orcynus subulatus, Orcynus albacora, Orcynus macropterus, Germo macropterus, Thunnus macropterus, Thunnus allisoni, Germo argentivittatus, Germo allisoni, Neothunnus macropterus, Neothunnus catalinae, Neothunnus albacores, Neothunnus allisoni, Kishinoella zacalles, Semathunnus guildi, Semathunnus itosibi, Neothunnus argentivittatus, Germo albacora, Thunnus albacora, Germo itosibi, Neothunnus albacora brevipinna, Neothunnus albacora longipinna, Neothunnus macropterus macropterus, Neothunnus macropterus itosibi, Neothunnus brevipinna, Thunnus zacalles, Thunnus catalinae, Neothunnus albacares, Thunnus albacores, Neothunnus albacora macropterus, Thunnus albacares macropterus, and Thunnus itosibi.

English language common names referring to this tuna include yellowfin tuna, yellow fin tuna, allison tuna, long fin tunny, longfin, Pacific long-tailed tuna, and tuna. Other common names include a'ahi (Tahitian), ahi (Hawaiian), albacora (Portuguese), badla-an (Tagalog), bakulan (Malay), chefarote (Creole/Portuguese), gelang kawung (Malay), jaydher (Arabic), kababa (Arabic), kelawalla (Sinhalese), kihada (Japanese), lamatra (Malagasy), maha'o (Hawaiian), otara (Tahitian), palaha (Hawaiian), rabil (Spanish), te baibo (Kiribati), thon jaune (French), thunfisch (German), tonno albacora (Italian), tonnos macropteros (Greek), tuna (Afrikaans), tunczyk zóltopletwy a. albakora (Polish), yatu (Fijian), zheltokhvostyj tunets (Russian), and zutorepi tunj (Serbian).

Yellowfin tunas are found worldwide in tropical and subtropical waters, from latitudes of approximately 40°N to 35°S. They are absent in the Mediterranean Sea. The yellowfin tuna is a highly migratory fish. In the Pacific Ocean, however, there is little evidence for long-range north-south or east-west migration. This suggests relatively little genetic exchange between the eastern, central, and western Pacific Ocean and perhaps the development of subspecies.

World distribution map for the yellowfin tuna

The yellowfin tuna is an epipelagic, oceanic fish, living above and below the thermocline, at temperatures of 65 to 88°F (18-31°C). It is generally found in the upper 330 feet (100 m) of the water column.

Schooling yellowfin tuna
courtesy National Oceanic and Atmospheric Administration

Yellowfin are strong schoolers. Their tendency to school with organisms of the same size is stronger than the tendency to school by species. They often swim in mixed schools of skipjack, bigeye, and other tunas. In the eastern Pacific Ocean, larger yellowfin frequently school in association with dolphins, particularly the spotted dolphin, spinner dolphin, and common dolphin. Such associations with dolphins have not been observed in the rest of the Pacific, the Indian, or the Atlantic Oceans. Yellowfin will commonly school under drifting objects such as driftwood, patches of seagrass, boats, or dead marine mammals. There are many hypotheses addressing the reasons for schooling under such items. Yellowfin may be attracted to the object to feed on smaller prey which are foraging on the structure. The drifting object provides shade and shelter from predators. Yellowfin tuna may utilize the object as a substrate on which to lay their eggs or as a "cleaning station," where parasites are removed by other fishes. Also, the fish may view the object as a "schooling companion".

Yellowfin swimming further from the surface are less likely to school, and tend to scatter. There is perhaps less benefit to schooling in such cases, as there are fewer predators and little reason to attempt to obtain food at depth.


Biology

Yellowfin tuna
courtesy National Park Service

· Distinctive Features

The yellowfin is a large tuna. Its body is strongly fusiform, and deepest under its first dorsal fin, while tapering considerably towards the caudal peduncle. Two dorsal fins are present. In adults, the second dorsal fin is very long, as is the anal fin, which is directly below the second dorsal. These fins become relatively longer in larger individuals. The pectoral fin is also long, reaching beyond the space between the dorsal fins. The caudal peduncle is very slender and includes three sets of keels. Seven to ten dorsal and ventral finlets are present. Scales are lacking behind the corselet, a band of large scales forming a circle around the body behind the head. A swim bladder is present. The eyes are small; teeth are small and conical.

Distinguishing characteristics of tunas
(NMFS ABT Tech Sheet No. 4)

Similar species occurring in the same areas as yellowfin tuna include bigeye tuna (Thunnus obesus), blackfin tuna (T. atlanticus), and albacore (T. alalunga). The bigeye tuna has shorter dorsal and anal fins than the yellowfin tuna and is generally a heavier and deeper-bodies fish. Blackfin tuna have dorsal and anal finlets that are dusky in color, rather than bright yellow with black margins as seen in the yellowfin and bigeye tunas. Albacore can be distinguished from the yellowfin with the size of the pectoral fins. The pectoral fins of the albacore are much longer than the yellowfin tuna, reaching to the second dorsal finlet in most cases. Also the caudal fin of the albacore has a white posterior edge which is lacking on the yellowfin tuna.

Yellowfin tuna
courtesy National Oceanic and Atmospheric Administration

· Coloration

The body is metallic dark blue or greenish above, while the belly and lower sides are silvery white and crossed by many vertical, interrupted lines. Perhaps most distinctly, a golden stripe runs along the side. The second dorsal and anal fins and finlets are bright yellow, and the finlets are bordered by a narrow band of black.

Yellowfin tuna
courtesy U.S. Food and Drug Administration

·Size, Age, and Growth

The maximum length reported for yellowfin is 110 inches (280 cm) total length and the maximum weight is 880 lbs. (400 kg). The all-tackle record recognized by the International Game Fish Association (IGFA) is 388 lbs. 8 oz. (176.4 kg). This latter example is more indicative of the common maximum size for the species.

Dolphin (Coryphaena hippurus) are common prey items of the yellowfin tuna
© Don DeMaria

· Food Habits

Primary prey items include fish, cephalopods, and crustaceans. Yellowfin appear to forage rather indiscriminately for any of these items. A study by Watanabe (1958) found 37 families of fish and 8 orders of invertebrates in yellowfin stomachs. Fish species consumed by the yellowfin tuna include dolphinfish, pilchard, anchovy, flyingfish, mackerel, lancetfish, and other tunas. Other prey items are cuttlefish, squid, octopus, shrimp, lobster, and crabs.

Yellowfin are apparently sight-oriented predators, as their feeding tends to occur in surface waters during daylight. Other large fish and marine mammals compete with yellowfin for food.

Yellowfin tuna larvae:
A. 5.1 mm NL, B. 6.0 mm SL, C. 8.5 mm SL, D. 46.0 mm SL
(NOAA Tech Memo NMFS-SEFC-240)

· Reproduction

Size at maturity varies by region, and may also be different between individuals found near- and offshore. All yellowfin are reproductively mature by the time they reach a length of 47 in. (120 cm) fork length (corresponding to an age of 2-3 years), however some are mature by 20-23 in. (50-60 cm) fork length (corresponding to 12-15 months). In juvenile fishes and adults up to 55 in. (140 cm), the sex ratio is approximately 1:1. The proportion of females declines in fishes larger than this size, however the reason for this is not understood.

Reproduction occurs year-round, but is most frequent during the summer months in each hemisphere. It is believed that 79°F (26°C) is the lower temperature limit for spawning. In the tropical waters of Mexico and Central America, it has been determined that yellowfin spawn at least twice a year. Each female spawns several million eggs per year. Among tunas, larval yellowfin can be identified by the presence of a single spot of black pigment under the chin and a lack of pigment on the tail. In profile, the center of the eye is above the line of the body axis. Postlarvae and small juveniles are very difficult to distinguish from related species because these diagnostic characters become obscured. The juveniles grow quickly, weighing approximately 7.5 pounds (3.4 kg) at 18 months and 140 pounds (63.5 kg) at 4 years.

Blacktip sharks (Carcharhinus limbatus) feed on yellowfin tuna
© David Snyder

· Predators

Sharks, including the bignose shark (Carcharhinus altimus), blacktip shark (Carcharhinus limbatus), and cookiecutter shark (Isistius brasiliensis), prey upon yellowfin tuna. Large bony fishes are also predators of the yellowfin tuna.

· Parasites

The yellowfin tuna is a known host to 40 parasites including protozoans, digenea (flukes), didymozoidea (tissue flukes), monogenea (gillworms), cestoda (tapeworms), nematoda (roundworms), acanthocephala (spiny-headed worms), copepods, isopods, as well as other fish including the cookiecutter shark (Isistius brasiliensis), largetooth cookiecutter shark (Isistius plutodus), and the pilotfish (Naucrates ductor).

Tuna boat with purse seine searching for tuna
courtesy Dann Blackwood/U.S. Geological Survey

Tuna catch: yellowfin, skipjack, and bigeye tuna aboard tuna fishing vessel
© Craig Knickle

Yellowfin tuna fillets
courtesy U.S. Food and Drug Administration

Yellowfin tuna catch
© Craig Knickle