Bannerfish (Genus Heniochus)

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By Roxy Bezuidenhoud

There are eight known species of the Genus Heniochus, which is a member of the Butterflyfish family Chaetodontidae, meaning "bristle teeth" in reference to their prising snout and dentition. All eight species are similarly shaped with laterally compressed sides, a pointed rostrum and a lengthened fourth dorsal ray.

The Chaetodontidae are very colourful fishes that are popular with divers and aquarists. The family consists of ten genera with about 120 species. They mostly inhabit coral reefs but some have become adapted to temperate and deep waters. The geographical distribution is mainly focused on the Red Sea and Arabian Sea coral reefs, 4 are found in the east Pacific and 12 in the Atlantic. The genus Chaetodon is the largest in the family, with 114 species in 13 sub-genera. Heniochus as mentioned above comprises 8 species, with the remaining genera being single species (monotypic), or with only a few species each.
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Most species inhabit the shallows of coral reefs, living in pairs or in large schools. The diet typically consists of coral polyps and hydroids, and small invertebrates such as polychaete worms; some are adapted to live on zooplankton. Butterflyfish produce tiny spherical pelagic eggs about 1mm in diameter, and the larvae have a bony head amour, often with serrated spines. These larval stages are in the region of 10mm long and settle among corals and rocks.

Of the eight species of Heniochus, two are common to the Red Sea: the Red Sea Bannerfish (Heniochus intermedius), and the Schooling Bannerfish (Heniochus diphreutes). The other species are the Long-Fin Bannerfish (Heniochus acumminatus), Pennant Butterflyfish (Heniochus chrysostomus), Masked Bannerfish (Heniochus monoceros), Phantom Bannerfish (Heniochus pleurotaenia), Humphead Bannerfish (Heniochus varius) and Singular Bannerfish (Heniochus singularius).

The Red Sea Bannerfish can grow up to 20cm and is found also in the western Gulf of Aden. It lives at depths between 3 and 50 meters, feeding on zooplankton during the day. These fish swim in pairs but are also found in groups of up to 24. Juveniles are found primarily at the base of reefs, living in larger groups.

In the Red Sea, these fish feed most actively at sunset and during the night, so divers may be less likely to see many Bannerfish in the daytime, as they may be hiding among corals.

The Red Sea Bannerfish appears to be a generalist feeder. It has been reported as a benthic feeder eating mostly sedentary polychaetes and some corals and other invertebrates off Eritrea, but as a planktonic feeder on larvaceans in the Gulf of Aqaba. It has a short gut, indicating that it doesn't eat algae and corals as much as some other butterfly fish species, but it is likely that it consumes some.

These fish are very territorial, with the territory often having a table coral at its centre. In the late afternoon, pairs of fish move to the borders of the territory to challenge neighbouring fish of the same species, whilst others within the same genus pass across the territory unchallenged.

Schooling Bannerfish grow up to 18cm and are characterised by an elongated 4th dorsal spine. They have two black bands, the second starting behind the dorsal filament, yellow pectoral, dorsal and caudal fins, with a grey spotted snout and nape. They live along the reef front or external reef, in large schools swimming in mid water.

It resembles another Heniochus species, Heniochus acuminatus, but is smaller, with shorter snout, snout and nape spots lighter, and usually lives in large schools.

These fish are found not only in the Red Sea through to the Arabian Gulf, but are widespread also in the Indian Ocean. They inhabit depths from 1 to 210 meters, living in aggregations in the water column above the reef tops, feeding on zooplankton. Juveniles are found living closer to the bottom near reef patches, whilst adults spend the entire day in open water, protected by the schooling behaviour.

Schooling Bannerfish are typical Plankton feeders, with juveniles also acting as cleaners, feeding on parasites collected on other fish skin.

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This page contains a single entry by Bryony published on July 1, 2010 1:03 PM.

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