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Animalia >Chordata >Osteichthyes >Perciformes >Scaridae >Scarus >

Divers often tell us that they can hear the sounds of parrotfishes scraping corals. Do parrotfishes really eat live corals? In the picture, a TP male of the bullhead parrotfish (Scarus sordidus) is foraging in an area of dense branching corals. It is hard to tell what exactly the fish is picking at. The fish, in fact, is not picking at a live coral. Rather, it is picking at a dead coral skeleton. It is eating filamentous algae growing on the surface of dead corals. Only the Green humphead parrotfish (Bolbometopon muricatum) mainly feed on live corals. The other species eat algae together with the dead-coral substratum. That is why they produce a cloud of calcareous powder as their feces (See also a video picture ¡ÆSpawning behavior of Bower¡Çs parrotfish (Scarus bowersi)).
In the next scene, a violet-lined parrotfish (Scarus globiceps) is foraging in an area of bear rock beds, which was created when a boat struck the reef. The boat destroyed live corals and exposed the rock beds. The fish is scraping the rock surface until the surface becomes very smooth. Although you can not see at a glance, there are small algae growing on the rock surface. The name ¡Æparrotfishes¡Ç come from the fact that these fishes have teeth that resemble the bills of parrots. At low tape speed, you can see the fish is sort of banging the teeth to the rock and scraping algae together with parts of the rock surface.
In the next scene, you see a TP male of the Rivulated parrotfish (Scarus rivulatus). It came to the shallow water and scraping the dead portion of Porites corals. There are tooth marks on live parts of Porites corals as well. It is suspected that these tooth marks are made by parrotfishes. But we rarely see parrotfishes actually eating live Porites corals. It is also uncertain whether parrotfishes are damaging live Porites corals. For the other corals at least, parrotfishes seems to be friends rather than enemies. It is hypothesized that removal of algae by herbivorous fishes, such as parrotfishes and tangs, facilitates recovery of corals after mass coral death.

TP males are males that are more brightly colored than females. There is another type of males, which is smaller than TP males and has coloration similar to that of females. The latter type of males is called initial-phase (IP) males. (translated by Asoh)

(Data No.momo060212ss02b)

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