Colourful Coral Associates
This group of fishes is characterised by its vibrant colours and similar habitat associations. Most of the animals in the group feed on invertebrates, such as sponges, coral, crustaceans and worms.
A pair of bannerfish - one of the colourful coral associates of the Great Barrier Reef
Reef fish are able to see colour. Their bright colours are important in species recognition and in the determination of sex. Some species, such as angelfish, have juvenile patterns that are totally different to the adults. The different colour patterns of juveniles may prevent adults from seeing them as a potential threat to territories or as reproductive partners.
The use of colour to blend with the environment is an import way to ambush prey and to hide from predators.
Some colourful coral associates
A clown anemonefish at home in an anemone
Anemonefish (or clownfish) live in close association with large sea anemones, each species having a preferred host. Anemonefish receive protection from predators by hiding amongst the tentacles of the anemone. In return, they protect the anemone from butterflyfish which feed on the tips of the anemone's tentacles.
A number of theories exist as to how the anemonefish prevent themselves from being stung. For example:
- The fish smear anemone mucus over themselves during elaborate dances, thus tricking the anemone into thinking the fish are part of the anemone; and
- The fish lack components in their own mucus that causes the anemone to sting other fish.
Anemonefish are normally found as a pair of adults and several juveniles. Being protandrous (change from male to female) hermaphrodites, the larger is the female and the smaller fish the male. If the female dies, the male changes sex and the largest juvenile becomes the new male. Eggs are laid at the base of the anemone and take up to 14 days to hatch.
A long-nosed butterflyfish
Butterflyfish are renowned for their striking colour patterns, delicate shapes and graceful swimming movements. They have deep, compressed bodies with small mouths, scales that extend onto the median fins and tiny bristle-like teeth from which they derive their Family name Chaetodontidae, which means bristle-like teeth.Their shape allows for manoeuvrability in and around corals when feeding. The diet differs among species; many feed on a combination of coral polyps, small invertebrates, fish eggs and filamentous algae.These fish are active during daylight hours and seek shelter amongst the reef structure during the night, often assuming a drab, nocturnal colour pattern. Butterflyfish often form pairs that may stay together for periods ranging from weeks to life. Butterflyfish also have colour patterns such as eye stripes and false eye spots which are used to confuse predators as to the direction in which the fish are swimming.
These fish are closely related to butterflyfish and share a number of similar characteristics such as deep, compressed bodies, scales that almost extend out onto the median fins and bristle-like teeth. They can, however, be identified by the presence of a spine in the corner of the gill covering (operculum). Typically most species are territorial and spend daylight hours near the bottom in search of food. The diet varies according to species: some feed on algae while others feed on sponges supplemented by a variety of benthic (bottom-dwelling) invertebrates. All species studied so far change sex from female to male. Each male defends his territory containing two to five females. Angelfish are also know for their dramatic colour changes from juvenile to adult stages, particularly in the genus Pomacanthus. The fish of this genus are also capable of startling divers with a powerful thumping sound which is produced by the airbladder of large adults.
A humbug - one of the smaller damselfish on the Reef
Damselfish are one of the most abundant groups of coral reef fishes. They display remarkable diversity in habitat preferences, feeding habits, behaviour and colouration. Most species are highly territorial. Algal-eating species zealously defend their 'plot' against intruders, regardless of size. These algal feeders. These algal feeders generally have drab colour patterns whereas the plankton-feeding damsels are brightly coloured. Damselfish eggs are laid on coral rock and are guarded by the male until they hatch in 2-14 days. All damselfish, except the anemonefish (genus Amphiprion and Premnas), change sex from male to female. The anemonefish goes through a reverse sex change from male to female.