The big parrotfish of this sea, up to 70 cm (28 in), blue-green with a steep blunt forehead and a beak heavy enough to hear from several meters away when it bites.
That sound is a reef being eaten. The fish takes coral rock along with the algae growing in it, mills the mouthful in a set of throat plates and passes out the mineral part as fine sand. A large parrotfish of this size produces something on the order of hundreds of kilograms of sand a year, and on a coral coast a good share of the beach passed through a fish first.
It sleeps in a cocoon of mucus like its smaller relatives, and it changes sex - the blue-green fish with the forehead is a male that began life as a dull brown female.
Because the big ones are the males and the males are the obvious targets, spearfishing hits this species hard, and reefs where these have gone are also reefs where algae start winning. Large fish in some areas carry ciguatoxins.
The species.Chlorurus gibbus (Rüppell 1829) - hump. ETYFish
How to recognise it
large blue-green fish with a steep blunt forehead in males
heavy fused beak, pale against the darker head
females and juveniles dull gray-brown with a pale tail base
length up to 70 cm
Why it's threatened
There are no major threats known for this species.
Parrotfishes show varying degrees of habitat preference and utilization of coral reef habitats, with some species spending the majority of their life stages on coral reefs, while others primarily utilize seagrass beds, mangroves, algal beds, and /or rocky reefs. Although the majority of the parrotfishes occur in mixed habitat (primarily inhabiting seagrass beds, mangroves, and rocky reefs) approximately 78% of these mixed habitat species are experiencing greater than 30% loss of coral reef area and habitat quality across their distributions. Of those species that occur exclusively in coral reef habitat, more than 80% are experiencing a greater than 30% of coral reef loss and degradation across their distributions. However, more research is needed to understand the long-term effects of habitat loss and degradation on these species populations. Widespread coral reef loss and declining habitat conditions are particularly worrying for species that depend on live coral reefs for food and shelter especially as studies have shown that protection of pristine habitats facilitate the persistence of adult populations in species that have spatially separated adult and juvenile habitats. Furthermore, coral reef loss and declining habitat conditions are particularly worrying for some corallivorous excavating parrotfishes that play major roles in reef dynamics and sedimentation (Comeros-Raynal et al. 2012).
Threat classification from the IUCN Red List.
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