A slim silver-blue mackerel to 36 cm (14 in), marked with fine dark wavy lines along the back and a golden spot behind the eye, with finlets running to the tail. Schools move fast and turn as one, and they are one of the few open-water fish a shore snorkeler regularly sees.
Feeding is filtration at speed. The fish swims through a plankton patch with the mouth wide open and the gill covers flared, straining the water through long comb-like gill rakers - so a mackerel school passing overhead has its mouths hanging open, which looks like a malfunction and is not.
The rakers change with the diet. Fish feeding on larger prey use them less and take individual items instead, and the same species can switch between filtering and picking depending on what the water is carrying.
It is one of the most important food fishes in the 🌊 Indian Ocean, landed by the hundred thousand tonnes and eaten fresh, dried and salted from East Africa to 🇮🇩 Indonesia. On the reef its role is simpler: it converts plankton into a mid-sized fish, which is what everything larger is waiting for.
The genus.Rastrelliger Jordan & Starks 1908 - rastrella (diminutive of rastrum) + -iger (to bear). ETYFish
How to recognise it
slim silver-blue fish with dark wavy lines along the back and a golden spot behind the eye
row of small finlets between the second dorsal fin and the tail
swims with the mouth wide open when feeding, gill covers flared
Rastrelliger kanagurta is harvested for human consumption through most of its range (Collette 1984). Rastrelligerkanagurta is also caught as bycatch in shrimp trawls, gill net, and trap fisheries (B. Collette, W. Smith-Vaniz, Q. Alghawzi, E. Abdulqader, J. Bishop, F. Kaymaram, and S. Hartmann pers. comm. 2013).
Threat classification from the IUCN Red List.
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