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The International Union for Conservation of Nature (IUCN) has assessed the Caribbean reef shark as Near Threatened; its population has declined off Belize and Cuba from overfishing and exploitation continues in other regions. They are also threatened by the degradation and destruction of their coral reef habitat. Commercial fishing for this species is prohibited in United States waters. They are protected in the Bahamas due to their significance to ecotourism, as well as in a number of Marine Protected Areas (MPAs) off Brazil and elsewhere. However, enforcement against illegal fishing is lacking in some of these reserves, and many areas in which this species is abundant are not protected.
Caribbean reef sharks are sometimes seen resting motionless on the sea floor or inside caves; it is the first active shark species in which such a behavior was reported. In 1975, Eugenie Clark investigated the famed "sleeping sharks" inside the caves at Isla Mujeres off the Yucatan Peninsula, and determined that the sharks were not actually asleep as their eyes would follow divers. Clark speculated that freshwater upwellings inside the caves might loosen parasites on the sharks and produce an enjoyable "narcotic" effect. If threatened, Caribbean reef sharks sometimes perform a threat display, in which they swim in a short, jerky fashion with frequent changes in direction and repeated, brief (1–1.2 second duration) drops of the pectoral fins. This display is less pronounced than the better-known display of the grey reef shark (C. amblyrhynchos).
There is a variety of biotic reef types, including oyster reefs and sponge reefs, but the most massive and widely distributed are tropical coral reefs. Although corals are major contributors to the framework and bulk material comprising a coral reef; the organisms most responsible for reef growth against the constant assault from ocean waves are calcareous algae, especially, although not entirely, coralline algae.