Groupers are mostly demersal (benthic or bottom-oriented) fishes of tropical and subtropical areas, ranging from shallow coastal waters to moderate depths; the great majority of species occur in less than 200 meters. They are usually found over coral reefs, and rocky bottoms along the coasts.
Typical groupers have a stout body and a large mouth. They do not have many teeth on the edges of their jaws, but they have heavy crushing tooth palates inside they pharynx. Their mouth and gills form a powerful sucking system that can suck their prey in from a distance. They habitually eat fishes, squids, and crustaceans. They swallow their prey rather than biting pieces of it and that makes them easy to get hook by bait. Normally a squid bait can be used over and over again.
Groupers are some of the top predators on coral reefs. Their colouration and ability to change hues and shades to blend in with their surroundings allow them to camouflage and lie in wait for prey rather than chasing in open water. They will ambush, dash and strike the prey in short distance. Right after they suck the bait, they will normally go into the rocks or structure that is surrounding them. When threatened, they use their mouth to expand their gill covers digging them into rock cave sides to form their shelters. Their gill muscles are so powerful that it is very difficult to pull them out of a cave.
Groupers have diverse sexual patterns. Species can be either gonochorist, simultaneous hermaphrodite or protogynous hermaphrodite. In gonochorism each individual functions as either a male or a female throughout life, whereas simultaneous hermaphrodites are capable of reproducing as both male and female simultaneously. Protogynous hermaphroditism involves a sequential change of sex from female to male. Protogyny can be divided into two functional forms, monandry and diandry. In monandric protogyny all males are derived from functional females by sex change. In diandric protogyny, males may develop from mature females or directly from the juvenile phase.
There are 64 genera and approximately 521 species worldwide. Malaysia is represented by 15 genera and approximately 68 species.