Saint Helena butterflyfish
A butterflyfish endemic to St Helena and Ascension Island.
The Saint Helena butterflyfish (Chaetodon sanctaehelenae), also called the cunningfish, is a marine ray-finned fish in the family Chaetodontidae. It lives in the Atlantic Ocean around the British Overseas Territories of Saint Helena and Ascension Island, and stray individuals have been spotted as far north as Liberia and the Canary Islands. Its body is silvery-white with a vertical black band across the eye, a yellow tail base, and yellow dorsal and anal fins. The dorsal fin has 13 spines and 21 to 23 soft rays, while the anal fin has 3 spines and 19 soft rays. It can grow up to 18 centimetres (7.1 inches) long. This fish is common in shallow waters, often seen in pairs or large shoals. It is oviparous and monogamous, forming pairs during spawning. Its local name comes from its habit of nibbling bait off a hook without getting caught. Juveniles of the wrasse *Thalassoma sanctaehelenae* have been observed cleaning parasites off this butterflyfish. It frequently gathers in shoals to eat refuse dumped into Saint Helena harbour, and normally feeds on benthic invertebrates. The species was first formally described in 1868 by the German-born British zoologist Albert Günther. Some experts place it in the subgenus *Exornator*, while others consider its classification uncertain.
Quick Facts
- Taxon
- Chaetodon sanctaehelenae
Facts from the source article.
Lore & Background
The Saint Helena butterflyfish has a silvery-white body with a vertical black band running through the eye. The caudal peduncle is yellow, as are the dorsal and anal fins. The dorsal fin contains 13 spines and 21-23 soft rays, while the anal fin has 3 spines and 19 soft rays. This species attains a maximum total length of 18 centimetres. It is found in the southeastern Atlantic Ocean, endemic to the waters around the British Overseas Territories of Ascension and Saint Helena islands, with vagrants reaching as far north as Liberia and the Canary Islands. It is a common species of shallow waters, normally recorded in pairs or big shoals. It is oviparous and monogamous, forming pairs during spawning. Locally named cunningfish because it can nibble bait from a hook while avoiding the hook. Juveniles of Thalassoma sanctaehelenae have been recorded acting as cleaner fish, picking parasites off this species. They frequently gather in shoals to feed on refuse tipped into the Saint Helena harbour, and normally feed on benthic invertebrates. The species was first formally described in 1868 by the German-born British zoologist Albert Günther. Some authorities place it within the subgenus Exornator, but others consider it to be incertae sedis.
Reader's Guide
The Saint Helena butterflyfish is significant as an endemic species of the remote South Atlantic islands of St Helena and Ascension, contributing to the unique marine biodiversity of those British Overseas Territories. Its local name, cunningfish, highlights a notable behavioral adaptation: the ability to take bait from a hook without being caught, a trait that has earned it recognition among local fishers. The species also plays a role in the local ecosystem, as juveniles of Thalassoma sanctaehelenae act as cleaner fish, removing parasites from it. Its habit of gathering in shoals to feed on refuse in Saint Helena harbour illustrates its opportunistic feeding behavior, while its primary diet consists of benthic invertebrates. The taxonomic uncertainty—whether it belongs to the subgenus Exornator or is considered incertae sedis—reflects ongoing scientific discussion about its classification. First described by Albert Günther in 1868, the species has been recorded as a vagrant as far north as Liberia and the Canary Islands, indicating occasional long-distance dispersal.
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