“Reef fish behaviour” by Paul Humann, Ned DeLoachĪ/animals/fish/butterflyfish/ The juveniles are miniature versions of the adults with yellow colouration and 5 vertical black bars to their bodies. Males defending the egg nests will turn a blue colour and will attack any intruder. They eat algae, plankton, invertebrates, eggs off rocks and small fishes. The juveniles are bright yellow with a demarcated blue dorsum while the adults are a dusky brown maintaining a pale to yellow tail.Ībudefduf saxatilis are another type of Damselfish that have evolved to eat a broad diet and can live in different habitats. As it does not need to defend algal patches, they typically inhabit calm shallow regions and often take refuge in empty conch shells and rubble. This is a type of carnivorous damselfish. the Large Yellowtail Damselfish overlaps its feeding territory with the Dusky Damselfish however it is the Damselfish that is bullied into doing most of the protection. They only ever co-exist with other species to share resources if there is a dominance relationship Eg. Most damselfish inhabit a single type of habitat and have a preference for substrate. Blue Tangs have developed a way of penetrating the Damsel fish defences by swimming in groups. It is the males that fiercely defend the gametes during spawning. When their feeding area or egg nest is threatened they flare their fins and dart back and forth ready to attack. They are very territorial and are known to nip at intruders. They have very small mouths with fine teeth and feed on algae. ![]() The juvenile of these species are often brightly coloured while the adults are normally of dark colouration. Surgeon fish play a key role to the reef by grazing on algae therefore inhibiting the growth of turf algae and in the process they increase the amount of detritus to the habitat for other species. Their digestive system is anatomically alike to a herbivore but because most of the substrate of a reef contains hydroids and micro invertebrates which are inadvertently eaten, all three species are considered omnivores. The juvenile of the species has a bright yellow tail which slowly changes to blue as it matures. Blue Tangs have flat oval heads and are dark blue to purple in colour with white spine grooves at the tail base. Both species can lighten or darken in colour dramatically. Doctorfish look very similar to Oceanic Surgeonfish however they have distinguishing body bars on either side. They are often found in mixed groups grazing on the algae on reefs. ![]() The three species in this group are the Blue Tang, the Oceanic Surgeonfish and the Doctorfish. The name is derived from the sharp spines on the either side of their tail base, they are normally folded forward in a groove and cannot be voluntarily erected. They use their dorsal spines to warn off predators and the false eye spot on juveniles and Foureye species assist to misdirect attacks. They feed on small worms, hydroids or coral polyps, particularly Gorgonian coral, and swim in pairs. Normally a silver colour with yellow tint and dark strips which cover the eyes. Generally of small size with concave heads and a protruding mouth housing teeth, makes them distinguishable to Angel fish. The Caribbean houses only seven of the 120 species of Butterfly fish. The Grey Angelfish is known to congregate in numbers of up to 20 as has been noticed over “ The Silent Evolution” on several occasions. The Grey and French Angel fish do not change sex and often live in a monogamous relationship with a similar sized partner for life. Sometimes when the head male disappears, the largest female will change sex. Some species live in harems and territory is fiercely protected by the group. They have evolved strong jaws with overlapping rows of teeth to eat the tough fibre of a sponge. Adult fish largely feed on sponges and move from colony to colony of sponges but do never devour an entire sponge. Juvenile Angelfish are brightly marked, this signifies their behaviour as cleaners, removing parasites from other larger reef fish and therefore less likely to become prey. ![]() ![]() Angelfish differ from butterfly fish by the well developed preopercular spine on their gill covers. Very attractive graceful swimmers with a round head and a long continuous dorsal and anal fin. Often the juvenile of a species is very different in appearance to the adult form. Most fish in this category are colourful and have small pert mouths.
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