Head to head
Wrasse vs Parrotfish
Parrotfish were long treated as their own family, but genetics places them firmly within the wrasses. They keep the classic wrasse traits of bright colour and sex change, and the main thing that sets them apart is the beak and the diet that goes with it.
| Wrasse | Parrotfish | |
|---|---|---|
| Classification | Family Labridae | A branch within Labridae |
| Teeth | Separate, often protruding | Fused into a hard beak |
| Diet | Invertebrates; parasites in cleaners | Algae and the surface film on coral |
| Role on the reef | Predator of shelled invertebrates | Grazer; major producer of reef sand |
| Colour | Bright, varied | Bright, often blue-green |
| Sex change | Common (female to male) | Common (female to male) |
| Mucus sleeping cocoon | A few species | Many species |
| Size range | 5 cm to over 2 m (humphead wrasse) | About 20 cm to 1.3 m (bumphead) |
Wrasse vs Parrotfish: common questions
Is a parrotfish really a type of wrasse?
Yes, according to current classification. Parrotfish were traditionally given their own family, Scaridae, because of their distinctive fused beak, but molecular studies consistently place them deep within the wrasse family, Labridae, as one specialised lineage rather than a separate branch. Many ichthyologists now treat parrotfish as a subfamily or tribe, Scarinae, inside Labridae. They share too much with wrasses to be separated: the same protogynous sex change, the same bright initial and terminal colour phases, the same general body plan, and the mucus cocoon habit. The beak and the algae-and-coral diet are the only major departures, and they evolved from within the group.
Do parrotfish really make sand?
Yes, and in large amounts on a healthy reef. When a parrotfish scrapes algae and the surface layer off coral rock, it takes in a lot of hard calcium carbonate along with the food. It grinds this in a powerful set of throat teeth, the pharyngeal mill, extracts the organic matter, and excretes the rest as a fine white sediment. A single large parrotfish can produce on the order of a hundred kilograms or more of sand per year, and on many tropical reefs and beaches parrotfish are estimated to be the source of a substantial share, sometimes most, of the white carbonate sand. Losing parrotfish to overfishing therefore affects not just algae control but sand supply.
Are parrotfish good or bad for coral reefs?
On balance strongly good, which is why they are protected in a growing number of places. By grazing down algae, parrotfish stop seaweed from smothering and outcompeting coral, and reefs with healthy parrotfish populations recover better after bleaching events and storms. They do bite living coral as well as dead rock, which removes some coral tissue, but across a reef this is far outweighed by the benefit of keeping algae in check. The main exceptions are the largest species, such as the bumphead parrotfish, which take big bites of live coral and, in high numbers, can slow coral recovery, but even there the algae-control role is generally seen as essential to reef health.