Grammatorcynus bilineatus

Scad Mackerel | Double-lined Mackerel
Grammatorcynus bilineatus
Grammatorcynus bilineatus, Great barrier Reef, Australia, Photo: Rick Stuart-Smith
Grammatorcynus bilineatus
Grammatorcynus bilineatus, Coral Sea, Australia, Photo: Andrew Green
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Grammatorcynus bilineatus
Grammatorcynus bilineatus


Tropical Indo-Pacific


Elongate silver body, greenish on back, double lateral line, lower line departing on perpendicular angle behind pectoral fin and re-joining on tail base. Common large mackerel around reefs, difficult to distinguish from G. bicarinatus (Shark Mackerel), which also has 2 lateral lines, but has proportionally smaller eye.


Max Size: 100 cm

Sea Temperature Range: 22.4-31.2°C

Depth: 1-50m

Habitat Generalization Index: 0.37

Also referred to as the SGI (Species Generalisation Index), this describes the habitat niche breadth of the species. Species with values less than 15 are found in a relatively narrow range of reef habitat types (specialists), while those over 25 may be found on most hard substrates within their range (generalists). Learn more here.

Conservation and Rarity

IUCN Status: Least Concern

Occurrence: Infrequent (4.5% of sites)

Occurrence describes how often the species is found on surveys within its distribution. It is calculated as the % of reef sites surveyed by RLS divers across all the ecoregions in which the species has been observed

Abundance: Few (2 per transect)

Abundance is calculated as the average number of individuals recorded per RLS transect, where present.

Edit by: Joe Shields