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Generalized carnivores

Carnivores are the most diverse of feeding types among coral reef fishes. There are many more carnivore species on the reefs than herbivores. Competition among carnivores is intense, resulting in a treacherous environment for their prey. Hungry predators lurk in ambush or patrol every part of the reef, night and day.

Some fishes associated with reefs are generalized carnivores that feed on a variety of animal prey. These typically have large mouths that can be rapidly expanded, thereby drawing in nearby water and any unfortunate animals contained within the inhaled water mass. The water is then expelled through the gills with the mouth closed, thereby trapping the helpless prey For example, the bluestripe snapper has a varied diet, feeding on fishes, shrimps, crabs, stomatopods, cephalopods and planktonic crustaceans, as well as plant and algae material. Diet varies with age, location and the prevalent prey items locally.

Goatfish are tireless benthic feeders, using a pair of long chemosensory barbels (whiskers) protruding from their chins to rifle through the sediments in search of a meal. Like goats, they seek anything edible: worms, crustaceans, molluscs and other small invertebrates are staples. The yellowfin goatfish (Mulloidichthys vanicolensis) often schools with the blue-striped snapper. The yellowfins change their colouration to match that of the snapper. Presumably this is for predator protection, since goatfish are a more preferred prey than bluestripe snapper. By night the schools disperse and individual goatfish head their separate ways to loot the sands. Other nocturnal feeders shadow the active goatfish, waiting patiently for overlooked morsels.

Moray eels and coral groupers (Plectropomus pessuliferus) are known to cooperate with each other when hunting. Grouper are protogynous hermaphrodites, who school in harems that can vary greatly in size according to the population size and reef habitat. When no male is available, in each school the largest female shifts sex to male. If the final male disappears, changes to the largest female occur, with male behavior occurring within several hours and sperm production occurring within ten days.