Benthic carnivores (also referred to as benthivores) are one of two types of coral reef fishes that fall under the more general classification of carnivores (meat eaters).
As a group, carnivores make up the majority of fish species associated with coral reef ecosystems.
Benthivores (discussed on this page) are fishes that that browse and feed mainly on invertebrate animals found on, or very near, the sea floor of coral reef ecosystems.
The second type, called piscivores, are those carnivorous fishes that primarily feed by hunting other fishes, most commonly in the open waters well above coral reef substrates. Piscivorous coral reef fishes are discussed on another page of this five-page section on coral reef fishes.
It should be noted that the two categories are not necessarily mutually exclusive in all species. Some “benthivores” also will take small fishes if given the chance, and some carnivorous species may fed primarily as benthivores while still small but “switch” to feeding as piscivores when attaining sufficient size.
Benthic carnivores comprise the largest single feeding category among coral reef fishes in terms of the number of species employing the carnivorous life style. Coral reef environments offer a variety of substrate types on which to hunt and feed, and each of these in turn has a wide variety of different kinds of invertebrate animals that might serve as prey.
Some benthic carnivores are diurnal predators (feeding by day) while others are nocturnal or night time feeders. Some hunt mainly on coral reef substrates, while others prowl the sand flats and seagrass meadows in search of prey. Each of these hunting strategies requires different adaptations, and is one reason for the extraordinary diversity of coral reef fishes.
In general, benthic carnivores that feed on coral reef substrates do so by day, and for good reason. During daylight hours, most of their invertebrate prey are motionless and well concealed by day, making keen eyesight and precise attack movements, which are possible only under daylight conditions, a basic necessity for locating and capturing such prey. These fishes are generally inactive and hidden in the reef after dark.
An entire order of coral reef fishes has evolved to become specialized masters of this hunting strategy. These are the Tetraodontiformes, and include triggerfishes (Balistidae, pictured right), filefishes (Monacanthidae), trunkfishes (Ostraciidae), and puffers (Tetraodontidae).
All members of the order have the keen eyesight, precise movements, and specialized mouths needed to excel at this lifestyle.
All are also equipped with formidable defenses (e.g., stout spines, toxins) that prevent them from becoming easy prey themselves as they themselves hunt.
Other daylight benthic carnivores that hunt and feed on small invertebrate animal prey on reef surfaces include some small and cryptic fishes such as the blennies (Blennidae), gobies (Gobiedae), and wrasses (Labridae).
A few highly specialized groups of diurnal benthic carnivores, such as the butterflyfishes (pictured left), employ a different feeding strategy. These fishes nip off exposed parts of invertebrate prey (e.g., coral polyp tentacles) rather than consuming the entire animals.
A relative few benthic carnivores have the capacity to hunt in comparative safety out in sand and seagrass habitats by day. Most of these nonetheless remain relatively close to the reef where they can quickly seek shelter if threatened.
The most prominent of such fishes are the goatfishes (Mullidae), a group equipped with fleshy appendages called barbels located under the chin. These highly sensitive chemosensory structures allow the goatfishes to “smell” invertebrate prey buried under the sand.
The heavily armored trunkfishes are also often seen hunting in the open waters by day, sometimes quite distant from the reef. Their size and covering of bony plates rather than scales provides safety from all but the largest of piscivores.
Most of the prey items that inhabit seagrass meadows and sand plains remain buried in the sand by day, emerging only after dark to feed on the rich food resources provided by seagrasses, plankton, and one another. This creates a rich feeding opportunity for reef fishes able to take advantage of this night bounty.
Vision is of minimal use to reef fishes hunting after dark, so they instead rely on other senses; mainly touch, taste, smell, and the lateral line system (a low frequency sound detector) for locating prey.
The most prominent examples of this type of night hunter are the certain of the snappers (Lutjanidae) and grunts (Pomadasyidae, pictured right) that shelter on the reef by day and venture out into such the dangerous open waters of sand plains and seagrass meadows distant from the reef only under the cover of darkness.
These fishes must employ a suitable feeding strategy for capturing their victims under such conditions. Unlike most daylight predators who are equipped with keen vision and small, precision-feeding mouths, night predators must necessarily attack with less finesse.
They do this by suddenly expanding oversized mouths thereby creating a vacuum that draws nearby water and anything floating or swimming in it into the mouth cavity. The mouth is then quickly closed and the water expelled through the gill openings, which are equipped with fine comb-like strainers that retain the prey.
On Caribbean reefs, some species of nocturnal feeding grunts are known to travel in streaming schools as far as half mile or more from the home reef on their way to select foraging areas.
There, they disperse to feed as solitary hunters throughout the night. Well before dawn, the schools reassemble and follow underwater trails back to the home reef.
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