This is an adult blue parrotfish.  The supermale is the same color but has a square head! 


Parrotfish (Scaridae is the family name) are the most common plant eating (herbivorous) fish on the reef. parrot_thumb They come in a wide range of colors and sizes but all share a characteristic shape.  Their beak-like mouth is quite distinctive as they have teeth designed to scrape algae off of the rocks.  Many Parrotfish also have an interesting (or at least unusual) sex life!  In some species, the females are drab colored and dominated in herds by the colorful male.  The male (called the supermale to distinguish him from his non-dominant males who do not get to mate) spends most of his time keeping his "harem" in line"!  If the male of the herd dies, the largest female changes into a male (this type of sequential sex change is called protogynous hermaphrodite for a female becoming a male or protandrous hermaphrodite when a male becomes a female!).  In other species, one of the non-dominant males becomes a supermale and alters his coloration whereas males of some species simply mature and reproduce without any major alteration of colors.

Without herbivores such as parrotfish, the reef would become overgrown with algae.  This is a problem in areas where the herbivorous fish have been fished by humans to the point where their numbers are greatly reduced.  In Bermuda during the late 1980s, we saw a shift from fishing for groupers to fishing for herbivores and the numbers rapidly declined!  Only by banning fishing for these animals has the problem been averted, with increased numbers of parrotfish beginning to be seen around the island.