Rainbow parrotfish  (Scarus guacamaia)

The rainbow parrotfish is classified as Data Deficient (DD) on the IUCN Red List (1).

The rainbow parrotfish (Scarus guacamaia) is the largest herbivorous fish in the Atlantic (3), with males growing to lengths of 1.2 metres (2). As the name suggests, they are attractively coloured fish with deep green bodies. The fins are orange with streaks of green extending outwards towards the back and tail (2). There are two forms of males; ‘initial phase’ males are drab in colour and similar in appearance to females, whereas ‘terminal phase’ males are brightly coloured (4). Parrotfish are so-called because of their unusual mouthparts. The teeth are fused to form a tough parrot-like beak which is used to scrape algae and other organic matter from the surface of coral (4).

The rainbow parrotfish occurs in the western Atlantic, from Florida, Bermuda and the Bahamas to Argentina (2).

Associated with coral reefs at depths of 3 to 25 metres (2). At night, rainbow parrotfish retreat into crevices (2). Juveniles tend to occur in mangroves adjacent to the reef. The mangroves act as important nursery areas and provide food-rich and predator free safe-havens for the growing young (3).

This herbivorous fish uses its strong beak-like mouthparts to scrape algae and other plant matter from the surface of the coral (4). This maintains the health of the reef by keeping algae in check, which could otherwise overwhelm the delicate reef ecosystem (5).

An unusual feature of parrotfishes is that they are able to change sex, with females becoming fully functional males (4). In a population, rainbow parrotfish start off as either females or males (known as primary males). Females may at some point in their life become male (secondary males). Populations that have these two types of males are called ‘diandrous’, meaning ‘two-males’ (4). A terminal phase male defends a territory and a harem of females. If the male should die, the most dominant female will become the dominant male, her ovaries becoming functional male testes (4).

In areas where adult coral reef habitat is connected to mangrove nursery habitat, removal of the mangroves has resulted in the local extinction of rainbow parrotfish (3). The current rate of destruction of mangroves, which is greater than that of tropical rainforest, will have a serious effect on adjacent reef communities (3). There are also known cases of deaths caused by poisoning (2). Further threats facing reef ecosystems include pollution, global warming, over-fishing and coastal development (5).

It is clear that the habitat of this spectacular parrotfish, is facing a huge range of threats. A number of reef reserves have been established in which fishing and other human pressures are prevented (5). The current rate of mangrove removal is a great threat to the survival of this and many other reef species (3). Hopefully, now that the importance of mangroves to reef communities has been recognised, steps can be taken to try to limit their hitherto wanton destruction.

View information on this species at the UNEP World Conservation Monitoring Centre.

For more information on the conservation of mangroves: 

• Mangrove Action Project:
  www.mangroveactionproject.org