Frigate tunaFRI

FRI
~49 cm TL

Characteristic features:

  • Large median keel with 2 smaller keels on either side of caudal peduncle
  • 36–42 gill rakers on first gill arch
  • 8 dorsal finlets, 7 anal finlets
  • Interpelvic process single, large
  • Teeth small and conical in single series
  • Tongue with 2 longitudinal ridges
  • Body scaleless behind a scaled corselet

Colour:

Bluish black to purple above, silver below. Dorsal scaleless area containing ~15 vertical dark bars behind first dorsal fin.

Size:

Up to 50 cm TL and up to 1.84 kg in weight.1

Distribution:

Circumglobal in tropical and subtropical waters.

View FAO distribution map

Habitat:

Inshore pelagic, found from the surface to 200 m depth.

Biology:

Mostly eats small fishes particularly clupeids, but also squid and planktonic crustaceans including crab and stomatopod larvae. Length at 50% maturity estimates include 30.5 cm FL in India.2 Estimated maximum age is 4 years.3

Fisheries:

Caught by drift nets, beach seines, shore seines, purse seines, hook-and-line and by trolling.

Similar species:

Auxis rochei
Bullet tuna
Auxis rochei
Auxis rochei differs in having a narrower posterior end of corselet spanning 1–5 scales wide under origin of second dorsal fin (vs. 10–15 scales); bars on dorsal scaleless area more vertical (vs. oblique to nearly horizontal); dorsal scaleless area shorter, extending posterior of pectoral-fin tip (vs. longer, extending anterior of pectoral-fin tip) and 43–48 gill rakers on first gill arch (vs. 36–42).

 

Euthynnus affinis
Mackerel tuna
Euthynnus affinis
Euthynnus affinis differs in usually having around 3 black spots present between pectoral and pelvic-fin bases (vs. none), a narrow inter-dorsal space (vs. wide) and 29–34 gill rakers on first gill arch (vs. 36–42).

 

Katsuwonus pelamis
Skipjack tuna

Katsuwonus pelamis

Katsuwonus pelamis differs in having 4–6 dark, longitudinal stripes on belly (vs. none); a narrow inter-dorsal space (vs. wide); an interpelvic process of 2 short flaps (vs. single, large) and 53–63 gill rakers on first gill arch (vs. 36–42).

 

Sarda orientalis
Striped bonito
BIP
Sarda orientalis differs in having an interpelvic process of 2 short flaps (vs. single, large); body covered in small scales behind corselet (vs. a dorsal scaleless area); a narrow interdorsal space (vs. wide) and 8–13 gill rakers on first gill arch (vs. 36–42).

 

Thunnus spp.
True tuna
Thunnus albacares
Thunnus spp. differ in having an interpelvic process of 2 short flaps (vs. single, large); a body covered in small scales behind corselet (vs. a dorsal scaleless area) and a narrow interdorsal space (vs. wide).
Thunnus albacares

External links:

FishBase
The IUCN Red List of Threatened SpeciesTM

References

1.
IGFA. IGFA world record game fishes. International Game Fish Association Dania Beach, Florida. 2011;
2.
Muthiah C. Maturation and spawning of Euthynnus affinis, Auxis thazard and Auxis rochei in the Mangalore inshore area during 1979-82. CMFRI Bulletin. 1985;36:71–85.
3.
Collette BB, Cole K. Reproduction and development in epipelagic fishes. Reproduction and sexuality in marine fishes: patterns and processes University of California Press, Berkeley. 2010;21–63.