Doublesash Butterflyfish

Fascinating facts about the Doublesash Butterflyfish

• A 1921 paper by English ichthyologist Charles Tate Regan introduced the doublesash butterflyfish, naming it after Natal fisheries officer Harold Walter Bell-Marley, which reminds us how scientific names often honor the people who first bring a species to light.
• When you spot one of these fish, its body is only about 20 cm long – roughly the length of a standard ruler – yet its dorsal fin packs 11 spines and up to 24 soft rays, a reminder that even small reef dwellers carry surprisingly complex armor.
• From the warm waters of Delagoa Bay in Mozambique to Lambert's Bay on South Africa's Atlantic coast, this butterflyfish spans a narrow strip of southern African coastline, illustrating how some marine species specialize in a surprisingly limited geographic corridor.
• Divers can find them down to 120 m (about 390 ft) on both rock and coral reefs, as well as in estuaries, showing that the species can thrive across a wide range of underwater habitats, from bustling reefs to murkier river mouths.
• These fish form pairs for spawning and eat a mixed diet of macroalgae, polychaete worms, crustaceans, hydroids and ascidians.

At a glance

About the Doublesash Butterflyfish

The doublesash butterflyfish, Chaetodon marleyi, has a silvery-white body marked with three broad yellow-brown vertical bands, a fourth band through the eye, and a similarly coloured caudal peduncle. Its dorsal fin has 11 spines and 23-24 soft rays, the anal fin has 3 spines and 18-19 soft rays, and the caudal fin bears a yellow band. It reaches a maximum total length of about 20 cm and is found on rock and coral reefs as well as in estuaries along the southwestern Indian Ocean and the extreme southwestern Atlantic off southern Africa, from Delagoa Bay in Mozambique to Lambert's Bay in South Africa, at depths down to 120 m. The species is omnivorous, feeding on macroalgae and benthic invertebrates such as polychaetes, crustaceans, hydroids and ascidians, and it forms pairs for spawning.

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