Yellowfin tunaYFT

Thunnus albacares

Characteristic features:

  • Large median keel with 2 smaller keels on either side of caudal peduncle
  • Pectoral fins moderate in length with bluntly pointed tips
  • Second dorsal fin and anal fin yellow, more elongated in adults
  • 26–34 gill rakers on first gill arch
  • 10 dorsal finlets, 7–10 anal finlets
  • Interpelvic process with 2 flaps
  • A distinct notch in central portion of trailing edge of caudal fin
  • Ventral surface of liver without striations, right lobe elongated (Fig. 1)
  • Swimbladder usually deflated or partly inflated, occupying anterior portion of body cavity (Fig. 2)

Colour:

Dark blue-black above edged with a thin blue line, flanks and belly silver. Fresh specimens display a bright yellow mid-lateral band extending from the eye to the tail. A series of closely spaced vertical white/silver lines alternating with vertical rows of silver dots in the form of a chevron pattern occur from beneath the pectoral fin to the tail and extend above mid-lateral line. Fins yellow to yellowish, anal fin often tinged with silver. Finlets bright yellow sometimes with narrow black margin.

Size:

Up to 240 cm TL and up to 176.4 kg in weight.

Important conditions and life stages:

Small/juvenile (less than ~40 cm FL)

Small or juvenile Thunnus albacares less than ~40 cm FL can be confidently identified using a combination of the following external features:

  • Silver/white markings in regularly spaced, vertical lines and alternating lines of spots in the form of a chevron pattern, extending forward of pectoral-fin insertion
  • Obvious demarcation between marked and unmarked region below pectoral fin base (when in fresh condition)
  • Head shorter and smaller relative to fork length
  • Eyes smaller and rounder in shape
  • Pectoral fins short and rounded at tips
  • Torpedo-like body shape. Body profile forming a shallow arc from snout to caudal peduncle
  • Caudal fin sometimes yellowish
D. Itano. ~17 cm FL Thunnus albacares
© D. Itano. ~17 cm FL Thunnus albacares.
© D. Itano. ~33 cm FL Thunnus albacares
© D. Itano. ~34 cm FL Thunnus albacares.
Adult (greater than ~40 cm FL)

Adult Thunnus albacares can be confidently identified using a combination of the following external features:

  • Silver/white markings in regularly spaced, vertical bars alternating with spots in the form of a chevron pattern, extending to level with pectoral-fin insertion
  • Dark blue-black back may be separated from bright yellow mid-lateral band by a thin, bright blue band
  • Clear demarcation between marked and unmarked region below pectoral fin base (when in fresh condition)
  • Head shorter and smaller relative to fork length
  • Eyes smaller and rounder in shape
  • Pectoral fins moderate in length, not extending beyond second dorsal fin, bluntly rounded tip
  • Second dorsal fin and anal fin yellow, elongated
  • A distinct notch in central portion of trailing edge of caudal fin
adult <em>Thunnus albacares</em>
© D. Itano. ~90 cm FL Thunnus albacares.
© D. Itano. ~105 cm FL Thunnus albacares
© D. Itano. ~105 cm FL Thunnus albacares.
Fresh condition

Thunnus albacares in fresh condition can be confidently identified by a combination of the following external features:

  • Silver/white markings in regularly spaced, vertical bars alternating with spots in the form of a chevron pattern, extending to level with pectoral-fin insertion
  • Dark blue-black back may be separated from bright yellow mid-lateral band by a thin, bright blue band
  • Clear demarcation between marked and unmarked region below pectoral fin base
  • Head shorter and smaller relative to fork length
  • Eyes smaller and rounder in shape
  • Pectoral fins moderate in length, not extending beyond second dorsal fin, bluntly rounded tip (if intact)
  • A distinct notch in central portion of trailing edge of caudal fin
© D. Itano Thunnus albacares
© D. Itano ~50 cm FL Thunnus albacares.
© D. Itano Thunnus albacares
© D. Itano ~45 cm FL Thunnus albacares.
Less than fresh to poor condition

Thunnus albacares in less than fresh to poor condition may display faded, partial or absent markings and/or colouration. They may also display damaged fins and/or disfigured shape due to freezing, transport and storage. Individuals in this condition should be identified by using a combination of the following external features, and also internal features if external are unavailable:

  • Remnants of silver/white markings in regularly spaced, vertical bars alternating with spots in the form of a chevron pattern, extending to level with pectoral-fin insertion (if visible)
  • Eyes smaller and rounder in shape (if intact)
  • Pectoral fins moderate in length, not extending beyond second dorsal fin, bluntly rounded tip (if intact)
  • A distinct notch in central portion of trailing edge of caudal fin (if intact)
  • Ventral surface of liver without striations, right lobe elongated
  • Swimbladder usually deflated or partly inflated, occupying anterior portion of the body cavity
© D. Itano. ~90 cm FL Thunnus albacares. Less than fresh condition.
© D. Itano Thunnus albacares
© D. Itano. ~45 cm FL Thunnus albacares. Less than fresh condition.
YFT frozen
© S. Fukofuka. ~39 cm FL Thunnus albacares. Poor condition.
YFT poor condition
© D. Itano. ~68 cm FL Thunnus albacares

. Poor condition.

Distribution:

Found in warm temperate and tropical waters circumglobally.

View FAO distribution map.

Habitat:

Pelagic and oceanic. Found within a temperature range of 15–31 °C and at depths from the surface to 250 m.

Biology:

Feeds on various fishes, cephalopods and crustaceans. Schools by size, in same species or multi-species groups. Yellowfin are highly migratory, traveling large distances for feeding and spawning purposes. This species is fast growing and highly productive, but with length and age of maturity varying depending on location. In the Western Pacific, length at first maturity was recorded as 73 cm FL, with 50% of individuals becoming mature at 104.6–107.9 cm FL.1 In the Western Central Pacific Ocean the smallest recorded mature female was 84 cm FL, with an estimated 50% of females becoming mature at 95 cm FL.2 In the Eastern Pacific, length where 50% of individuals become mature ranged between 92–96 cm FL for females and males respectively, corresponding to ~2.1 years.3 Spawning occurs all year throughout their distribution where sea surface temperatures are 24 °C or above almost exclusively at night.3 Maximum age varies by location, estimates include 4.8 years in the Pacific,4 6.5 years in the Western Pacific5 and up to 8 years in the Atlantic.6

Indonesian fisheries:

A prominent species in the Indonesian tuna fisheries, both as juvenile and adult fish. Caught by several gear types including purse-seine, longline, pole and line, handline, troll-line and gill-net, and for all but longline and gill-net, the fishing frequently includes use of Fish Aggregating Devices (FADs). Adult yellowfin are caught by longline, by handline on FADs at depths of 150–250 m, and in surface waters using kite and lure fishing.

Similar species:

Thunnus alalunga
Albacore tuna
Thunnus alalunga differs in having very long pectoral fins, extending to second dorsal finlet  (vs. moderately long, not reaching posterior of second dorsal-fin base); white/silver horizontal to oblique, incomplete stripes present in stressed live, and freshly dead specimens only, no markings in long dead specimens (vs. white/silver body markings in regularly spaced, vertical lines and alternating lines of spots in a ‘chevron’ pattern); caudal fin with white posterior margin (vs. caudal fin yellowish/silver); ventral surface of liver without striations, right lobe elongated (vs. striations, lobes roughly equal in length) and  25–31 gill rakers on first gill arch (vs. 26–34).

 

Thunnus maccoyii
Southern bluefin tuna
Thunnus maccoyii differs in having short pectoral fins, not reaching interdorsal space (vs. moderately long, but not reaching posterior of second dorsal-fin base); a series of white/silver irregularly spaced, often broken or incomplete vertical stripes present in stressed live , and freshly dead specimens only (vs. white/silver body markings in regularly spaced, vertical lines and alternating lines of spots in a ‘chevron’ pattern); ventral surface of liver striated, lobes roughly equal in length (vs. not striated, right lobe elongate); 31–34 gill rakers on first gill arch (vs. 26–34) and a median keel yellow in adults (vs. dark).

 

Thunnus obesus
Bigeye tuna

Thunnus obesus

Thunnus obesus differs in having a greater head length and depth (vs. smaller) and larger eye diameter (vs. smaller) for a given FL; and being more elliptical in shape (vs. round); body deep and rounded (vs. more slender and elongate); pectoral fins very long, tips tapering to a thin flexible point (in adults) (vs. moderately long extending to base of second dorsal fin, broad and stiff); pectoral fins arc-shaped when viewed from above (vs. straight); white/silver body markings in irregularly spaced, sometimes broken, vertical lines only, mostly confined to the lower half and rear of the body (in fresh condition) (vs. white/silver body markings in regularly spaced, vertical lines and alternating lines of spots in a ‘chevron’ pattern on the upper and lower portion of the body (in fresh condition)); yellow finlets edged with black (vs. black edging thin or absent); the central portion of trailing edge of caudal fin a smooth crescent-shaped (vs. a distinct ‘V’ or ‘M’ shaped notch) and ventral surface of liver without striations, right lobe elongated (vs. striations, lobes roughly equal in length).

 

Thunnus orientalis
Pacific bluefin tuna
Thunnus orientalis differs in having short pectoral fins, never reaching past interdorsal space (vs. moderate length, not extending beyond end of second dorsal-fin base); white/silver markings as vertical lines and alternating lines of spots, mostly confined to lower portion of body (vs. white/silver body markings in regularly spaced, vertical lines and alternating lines of spots in a ‘chevron’ pattern) and ventral surface of liver striated, lobes roughly equal in length (vs. not striated, right lobe elongate).

 

Thunnus tonggol
Longtail tuna
Thunnus tonggol differs in having shorter pectoral fins, not reaching the origin of the second dorsal fin (vs. moderately long, reaching beyond the origin of second dorsal fin); posterior portion of body (from deepest point to caudal peduncle) long relative to FL (vs. moderate); horizontal rows of white/silver elongate spots on belly (vs. white/silver body markings in regularly spaced, vertical lines and alternating lines of spots in a ‘chevron’ pattern) and 19–27 gill rakers on first gill arch (vs. 26–34).

Internal links:

Thunnus albacares interactive learning
Thunnus albacares market gallery

External links:

FishBase
The IUCN Red List of Threatened SpeciesTM

 

References

1.
Itano DG. The reproductive biology of yellowfin tuna (Thunnus albacares) in Hawaiian waters and the western tropical Pacific Ocean: project summary. University of Hawaii, Joint Institute for Marine and Atmospheric Research Hawaii; 2000.
2.
Hampton J, Fournier DA. A spatially disaggregated, length-based, age-structured population model of yellowfin tuna (Thunnus albacares) in the western and central Pacific Ocean. Marine and Freshwater Research. 2001;52(7):937–63.
3.
Schaefer KM. Reproductive biology of yellowfin tuna (Thunnus albacares) in the eastern Pacific Ocean. Inter-Am Trop Tuna Comm Bull. 1998;21:201–72.
4.
Wild A. Growth of yellowfin tuna, Thunnus albacares, in the eastern Pacific Ocean based on otolith increments. Inter-American Tropical Tuna Commission Bulletin. 1986;18(6):421–82.
5.
Lehodey P, Leroy B. Age and growth of yellowfin tuna (Thunnus albacares) from the western and central Pacific Ocean as indicated by daily growth increments and tagging data. WP YFT-2, SCTB. 1999;12:16–23.
6.
IGFA. Database of IGFA angling records until 2001. IGFA Fort Lauderdale, USA; 2001.