Double-lined mackerelDBM

Grammatorcynus bilineatus
42.6 cm TL

Characteristic features:

  • Large median keel with 2 smaller keels on either side of caudal peduncle
  • 18–24 gill rakers on first gill arch
  • 2 lateral lines joining above pectoral fin
  • Eyes large
  • 11–13 dorsal-fin spines
  • Rectangular patch of sharp teeth on tongue
  • Body covered in moderately small scales, no corselet

Colour:

Blue–green above and silvery white below.

Size:

Up to 65 cm TL, and up to 3.5 kg in weight.1

Distribution:

Found in tropical waters of the Indo-West Pacific.

Habitat:

Pelagic, found in open waters and also associated with reefs, inhabiting both coral reefs, outer reef walls. Found at depths below 15 m.

Biology:

Feeds on fishes such as clupeids, Sphyraena and Balistes, and also crustaceans. Forms large schools. In waters off Fiji, length at first maturity is estimated at 40–43 cm FL.2 The spawning season extends from October to March.3

Indonesian fisheries:

Caught mainly by pole-and-line fishing and by trolling.

Similar species:

Gymnosarda unicolor
Dogtooth tuna
Gymnosarda unicolor
Gymnosarda unicolor differs in having a single, undulating lateral line (vs. 2 lateral lines); 2 patches of teeth on the tongue (vs. single rectangular patch); interpelvic process large and single (vs. small and single) and a body mostly scaleless behind a corselet of enlarged scales (vs. covered in moderately small scales).

 

Scomberomorus spp.
Seer fishes
Scomberomorus commerson
Scomberomorus spp. differ in having a single, undulating lateral line (vs. 2 lateral lines) and markings in the form of dark vertical bars or spots (vs. no markings).

 

Thunnus spp.
True tunas
Thunnus albacares
Thunnus albacares
Thunnus spp. differ in having lateral line single and undulating (vs. 2 lateral lines) and body covered in small scales behind a corselet of enlarged thickened scales (vs. a body covered in moderately small scales).

References

1.
Collette BB, Nauen CE. FAO species catalogue. Volume 2. Scombrids of the world. An annotated and illustrated catalogue of tunas, mackerels, bonitos and related species known to date. 1983.
2.
Silas EG. Synopsis of biological data on double-lined mackerel Grammatorcynus bicarinatus (Quoyand Gaimard)(Indo-Pacific). FAO Fisheries Biology Synopsis No 72 Species Synopsis No 29. 1963;811–33.
3.
Lewis A, Chapman L, Sesewa A. Biological notes on coastal pelagic fishes in Fiji. Fisheries Division (MAF); 1983.