The Blue Parrotfish — Scarus coeruleus — is an almost completely bright-blue species of parrot fish (Scarus). They are the only uniformly blue species of fish currently known of. They are also known as blue kwabs, bluemen, blue parrots, and kwabs.
The name “parrotfish” refers to the “beak-like” jaws and fused teeth of the species in the genus. These teeth are used to scrape algae off of rocks and corals. Strangely, they also possess what are known as Pharyngeal teeth, which are essentially just teeth in the throat. Parrot fishes use these teeth to grind rocks the rocks/corals that they ingest into sand, which is then eliminated, creating new sand. This actually leads to the formation of small islands and sandy beaches in the Caribbean. Individual parrot fishes can produce as much as 200 lbs of sand a year.
On average they grow to sizes of around 30-75 cm in length, but can grow at least as large as 1.2 meters. The males are generally larger than the females, they also tend to develop “humps” on their head. Their range extends throughout much of the Western Atlantic. They eat, primarily, algae and small animals that live in the sand.
Some species of parrotfish secrete a thick “cocoon” of mucus from their mouth before going to sleep, that then covers the animal. It’s thought that this helps to protect them from predators by hiding their scent.
They are currently labeled as “Least Concern” on the Endangered Species List, but they do remain vulnerable due to habitat destruction/coral reef death/bleaching.