Mackerel tunaKAW

Euthynnus affinis
31.6 cm TL

Characteristic features:

  • Large median keel with 2 smaller keels on either side of caudal peduncle
  • 29–34 gill rakers on first gill arch
  • 8–10 dorsal finlets, 6–8 anal finlets
  • Interpelvic process 2 flaps
  • Teeth small and conical in single series
  • Tongue with 2 longitudinal ridges
  • Narrow interdorsal space not wider than eye
  • Body scaleless behind a corselet of enlarged, thickened scales

Colour:

Bluish black above, silver below. Scaleless corselet area containing a series of oblique dark stripes behind mid-first dorsal fin. Usually 1–3 small dark spots between pectoral and pelvic-fin bases.

Size:

Up to 100 cm TL, and up to 14 kg in weight.

Distribution:

Warm waters of the Indo-West Pacific, including oceanic islands and archipelagos.

View FAO distribution map

Habitat:

Inshore pelagic, found at depths from the surface to 50 m.

Biology:

Mostly eats small fishes, particularly clupeids and atherinids, but also squids, crustaceans and zooplankton. Forms size segregated same species and multi-species schools. Maturity of Euthynnus affinis varies by region, off the coast of India, length at where 50% of individuals are mature is estimated at 49 cm FL and 49.7 cm FL for females and males respectively.1 In waters off Taiwan, age of first maturity is estimated at 2 years.2 Euthynnus affinis migrate to waters off the coast of Taiwan, north of the Philippines for spawning.3 Spawning season occurs from April to August, peaking in July.2 Maximum age is estimated at 9 years.4

Indonesian fisheries:

Caught in multi-species fisheries mainly by gill netting and surface trolling.

Similar species:

Auxis spp.
Bullet & Frigate tuna
Auxis rochei
Auxis rochei
Auxis spp. differs in having an interpelvic process of 2 short flaps, (vs. single, large); a wide interdorsal space (vs. narrow) and no spots between pectoral- and pelvic-fin bases (vs. usually 1–3 spots).

 

Katsuwonus pelamis
Skipjack tuna
Katsuwonus pelamis
Katsuwonus pelamis differs in having 4–6 dark, longitudinal stripes on belly (vs. none); no markings on dorsal scaleless area (vs. a series of oblique dark stripes) and 53–63 gill rakers on the first gill arch (vs. 43–48).

 

Sarda orientalis
Striped bonito
BIP
Sarda orientalis differs in having 5–1 narrow dark horizontal stripes on upper sides (vs. a series of oblique dark stripes); body entirely covered in minute scales behind a scaled corselet (vs. dorsal area scaleless behind a scaled corselet) and 29–34 gill rakers on the first gill arch (vs. 8–13).

 

Thunnus spp.
True tuna
Thunnus albacares
Thunnus albacares
Thunnus spp. differ in having a body entirely covered in minute scales behind a corselet of enlarged, thickened scales (vs. dorsal area scaleless behind a scaled corselet).

References

1.
Deepti VI, Sujatha K. Fishery and some aspects of reproductive biology of two coastal species of tuna, Auxis thazard (Lacepede, 1800) and Euthynnus affinis (Cantor, 1849) off north Andhra Pradesh, India. Indian Journal of Fisheries. 2012;59(4):67–76.
2.
Chiou W-D, Cheng L-Z, Chen K-W. Reproduction and food habits of Kawakawa Euthynnus affinis in Taiwan. 臺灣水產學會刊. 2004;31(1):23–38.
3.
Chiou W, Lee L. Migration of kawakawa Euthynnus affinis in the waters near Taiwan. Fisheries science. 2004;70(5):746–57.
4.
Abdussamad EM, Rohit P, Said Koya KP, Sivadas M. Status and potential of neritic tunas exploited from Indian waters. IOTC Second Working Party on Neritic Tunas, Malaysia. 2012;