One useful definition distinguishes reefs from mounds as follows: Both are considered to be varieties of organosedimentary buildups – sedimentary features, built by the interaction of organisms and their environment, that have synoptic relief and whose biotic composition differs from that found on and beneath the surrounding sea floor. Reefs are held up by a macroscopic skeletal framework. Coral reefs are an excellent example of this kind. Corals and calcareous algae grow on top of one another and form a three-dimensional framework that is modified in various ways by other organisms and inorganic processes. By contrast, mounds lack a macroscopic skeletal framework (see stromatolite). Mounds are built by microorganisms or by organisms that don't grow a skeletal framework. A microbial mound might be built exclusively or primarily by cyanobacteria. Excellent examples of biostromes formed by cyanobacteria occur in the Great Salt Lake in Utah, and in Shark Bay on the coast of Western Australia.
The Caribbean reef shark is the most common shark on or near coral reefs in the Caribbean. It is a tropical inshore, bottom-dwelling species of the continental and insular shelves. Although C. perezi mainly inhabits shallow waters, it has been recorded to reach depths to at least 98 feet (30 m). Caribbean reef sharks are commonly found close to drop-offs on the outer edges of coral reefs and also may lie motionless on the bottom of the ocean floor. This phenomenon has also been observed in caves off the coast of Mexico and off the Brazilian archipelago of Fernando de Noronha.
^ Garla, R.C.; Chapman, D.D.; Shivji, M.S.; Wetherbee, B.M.; Amorim, A.F. (2006). "Habitat of juvenile Caribbean reef sharks, Carcharhinus perezi, at two oceanic insular marine protected areas in the southwestern Atlantic Ocean: Fernando de Noronha Archipelago and Atol das Rocas, Brazil". Fisheries Research. 81 (2–3): 236–241. doi:10.1016/j.fishres.2006.07.003.
A profitable ecotourism industry has arisen around this species involving organized "shark feeds", in which groups of reef sharks are attracted to divers using bait. Some US$6,000,000 is spent annually on shark viewing in the Bahamas, where at some sites a single living Caribbean reef shark has a value between US$13,000 and US$40,000 (compared to a one-time value of US$50–60 for a dead shark).[14] This practice has drawn controversy, as opponents argue that the sharks may learn to associate humans with food, increasing the chances of a shark attack, and that the removal of reef fishes for bait may damage the local ecosystem. Conversely, proponents maintain that shark feeds contribute to conservation by incentivizing the protection of sharks and educating people about them. Thus far, there has been little evidence that shark feeds have increased the risk of attack in the surrounding area.[8][15] Shark feeding has been outlawed off the coast of Florida, but continues at other locations in the Caribbean.[4]

The Caribbean reef shark feeds on a wide variety of reef-dwelling bony fishes and cephalopods, as well as some elasmobranchs such as eagle rays (Aetobatus narinari) and yellow stingrays (Urobatis jamaicensis).[1] It is attracted to low-frequency sounds, which are indicative of struggling fish.[4] In one observation of a 2 m (6.6 ft) long male Caribbean reef shark hunting a yellowtail snapper (Lutjanus crysurus), the shark languidly circled and made several seemingly "half-hearted" turns towards its prey, before suddenly accelerating and swinging its head sideways to capture the snapper at the corner of its jaws.[8] Young sharks feed on small fishes, shrimps, and crabs.[8] Caribbean reef sharks are capable of everting their stomachs, which likely serves to cleanse indigestible particles, parasites, and mucus from the stomach lining.[11]


On the infrequent occasions when they swim in oceanic waters, grey reef sharks often associate with marine mammals or large pelagic fishes, such as sailfish (Istiophorus platypterus). There is an account of around 25 grey reef sharks following a large pod of bottlenose dolphins (Tursiops sp.), along with 25 silky sharks (C. falciformis) and a single silvertip shark.[13] Rainbow runners (Elagatis bipinnulata) have been observed rubbing against grey reef sharks, using the sharks' rough skin to scrape off parasites.[14]
One useful definition distinguishes reefs from mounds as follows: Both are considered to be varieties of organosedimentary buildups – sedimentary features, built by the interaction of organisms and their environment, that have synoptic relief and whose biotic composition differs from that found on and beneath the surrounding sea floor. Reefs are held up by a macroscopic skeletal framework. Coral reefs are an excellent example of this kind. Corals and calcareous algae grow on top of one another and form a three-dimensional framework that is modified in various ways by other organisms and inorganic processes. By contrast, mounds lack a macroscopic skeletal framework (see stromatolite). Mounds are built by microorganisms or by organisms that don't grow a skeletal framework. A microbial mound might be built exclusively or primarily by cyanobacteria. Excellent examples of biostromes formed by cyanobacteria occur in the Great Salt Lake in Utah, and in Shark Bay on the coast of Western Australia.
×