The groupers are found in several different genera in the subfamily Epinephelinae in the family Serranidae. The family Serranidae is also where you will find the closely related sea basses. The word grouper is derived from the word garoupa, which means fish in a Russian dialect spoken in a part of Siberia. In Australian English, the word grouper is sometimes spelled groper and Epinephelus lanceolatus is for instance commonly referred to as the Queensland Groper instead of Queensland Grouper.
When a fish has the word “grouper” in its common name, it will normally belong to the genus Epinephelus or Mycteroperca. There are however exceptions to this general rule and you can for instance find fish called groupers in genera such as Anyperidon, Cromileptes, Dermatolepis, Gracila, Saloptia and Triso, and the genus Plectropomus is home to the so called coral groupers.
Many Groupers are appreciated food fishes and some of them are aquacultured. Most consumers prefer to purchase live groupers in fish markets instead of buying frozen fishes or fillets. Groupers are also appreciated by sport fishers and can put up quite a fight. Most species of grouper are too big to be kept by aquarists, but a few species have been successfully kept in home aquariums. It is however very important to research the maximal size of the species you are interested in before you make a purchase since groupers can outgrow the aquarium rapidly.
Many species of grouper can grow really large and exceed 100 cm (over 3 feet) in length. Weights around 100 kg (220 pounds) are not uncommon, and some really large specimens have been caught that weighed almost 180 kg (400 pounds). The species Epinephelus lanceolatus (Bumblebee grouper) is known to grow especially larger and there are many unverified reports of huge specimens form South-East Asia.
A grouper will typically have a stout body with a larger mouth and it is not a very fast long-distance swimmer. Groupers prefer to ambush prey rather than chase after it. The mouth and the gills are used to suck the prey in from a distance and the large mouth of the grouper is used to swallow the caught animal whole. The edges of the jaw are fairly toothless, but the grouper is equipped with tooth plates inside its throats that are used to crush prey. Generally speaking, groupers will eat fish, lobsters, crabs and octopus.
Groupers can protect themselves by digging out shelters under big rocks. They fish fills its large mouth with sand and jets it out through the gills and this makes the grouper a highly efficient digger. When a grouper feels threatened, it will seek shelter in its dug out cave and extend its gills. Once the gills are extended it is extremely hard to pull a grouper out of its hiding spot because the gill muscles are extremely strong.Groupers are protogynous hermaphrodite, i.e. a majority of the young specimens are female but will turn into males as their size increases. They will normally turn into breeding females when they weigh around 3 kg (6-7 pounds) and stay female until they weigh around 10-12 kg (22-27 pounds). The male fish will try to form a harem consisting of several females and breed with all of them.