Order : Perciformes
Family : KYPHOSIDAE
Species : As of 2024, 16 species in 2 genera (Kyphosus and Neoscorpis)
Maximum Length : 90 cm in Kyphosus incisor

Sea chubs (Kyphosus spp. and Neoscorpis lithophilus) comprise a group of 16 species in the family Kyphosidae (Fishbase, 2024).

These near-shore marine and brackish water fishes are widely distributed in the Pacific, Indian and Atlantic oceans, as well as the warm, tropical waters of Southeast Asia; at least 4 species occur within coastal Southeast Asia seas.

The largest member of the family is Kyphosus incisor (Yellow Sea Chub) which grows up to 90 cm total length, however most other species reach maximum sizes of around 40 to 80 cm. Most are strictly herbivorous, feeding on marine algae (seaweed).

Kyphosus cinerascens, (Blue Sea Chub, Topsail Sea Chub), featured here, ranges throughout Southeast Asia. It typically reaches a maximum length of 45 cm, but may occasionally grow up to 53 cm (Fishbase, 2024). Its colour is typically bluish-grey, sometimes brownish, with dark lines on the flanks. Its body is laterally compressed, and its tail fin is emarginate (i.e. slightly forked). It feeds mainly on marine algae (seaweed), albeit with associated invertebrates.

Fig 1 : Blue Sea-chub (Kyphosus cinerascens) in shallow coastal water at Tioman Island, Peninsular Malaysia. 

Fig 2 : Warm, shallow, tropical marine habitat at Tioman Island, Peninsular Malaysia, in the South China Sea.

Fig 3 : Dorso-lateral view of Blue Sea-chub. At the bottom right of this image is an Indo-Pacific Sergeant (Abudefduf vaigiensis).


Links and references :

Fishbase - Kyphosidae

Fishbase - Kyphosus cinerascens