The snout is rather short, broad, and rounded, without prominent flaps of skin beside the nostrils. The eyes are large and circular, with nictitating membranes (protective third eyelids). There are 11–13 tooth rows in either half of both jaws. The teeth have broad bases, serrated edges, and narrow cusps; the front 2–4 teeth on each side are erect and the others increasingly oblique. The five pairs of gill slits are moderately long, with the third gill slit over the origin of the pectoral fins.[4] The first dorsal fin is high and falcate (sickle-shaped). There is a low interdorsal ridge running behind it to the second dorsal fin, which is relatively large with a short free rear tip. The origin of the first dorsal fin lies over or slightly forward of the free rear tips of the pectoral fins, and that of the second dorsal fin lies over or slightly forward of the anal fin. The pectoral fins are long and narrow, tapering to a point.[2] The dermal denticles are closely spaced and overlapping, each with five (sometimes seven in large individuals) horizontal low ridges leading to marginal teeth.[4]
The "hunch" threat display of the grey reef shark is the most pronounced and well-known agonistic display (a display directed towards competitors or threats) of any shark. Investigations of this behavior have been focused on the reaction of sharks to approaching divers, some of which have culminated in attacks. The display consists of the shark raising its snout, dropping its pectoral fins, arching its back, and curving its body laterally. While holding this posture, the shark swims with a stiff, exaggerated side-to-side motion, sometimes combined with rolls or figure-8 loops. The intensity of the display increases if the shark is more closely approached or if obstacles are blocking its escape routes, such as landmarks or other sharks. If the diver persists, the shark will either retreat or launch a rapid open-mouthed attack, slashing with its upper teeth.[3]
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Are there so few reef sharks because of human activities such as fishing and finning, or were there never very many to start with? To answer this question, a team of marine biologists (which did not include Friedlander) decided to count reef sharks at coral reefs close and far to human settlements to better understand how humans impact their populations.
During mating, the male grey reef shark will bite at the female's body or fins to hold onto her for copulation.[13] Like other requiem sharks, it is viviparous: once the developing embryos exhaust their supply of yolk, the yolk sac develops into a placental connection that sustains them to term. Each female has a single functional ovary (on the right side) and two functional uteruses. One to four pups (six in Hawaii) are born every other year; the number of young increases with female size. Estimates of the gestation period range from 9 to 14 months. Parturition is thought to take place from July to August in the Southern Hemisphere and from March to July in the Northern Hemisphere. However, females with "full-term embryos" have also been reported in the fall off Enewetak. The newborns measure 45–60 cm (18–24 in) long. Sexual maturation occurs at around seven years of age, when the males are 1.3–1.5 m (4.3–4.9 ft) long and females are 1.2–1.4 m (3.9–4.6 ft) long. Females on the Great Barrier Reef mature at 11 years of age, later than at other locations, and at a slightly larger size. The lifespan is at least 25 years.[4][20][24]
Reproduction is viviparous; once the developing embryos exhaust their supply of yolk, the yolk sac develops into a placental connection through which they receive nourishment from their mother. Mating is apparently an aggressive affair, as females are often found with biting scars and wounds on their sides.[4] At the Fernando de Noronha Archipelago and Atol das Rocas off Brazil, parturition takes place at the end of the dry season from February to April, while at other locations in the Southern Hemisphere, females give birth during the Amazon summer in November and December.[4][12] The average litter size is four to six, with a gestation period of one year. Females become pregnant every other year.[8] The newborns measure no more than 74 cm (29 in) long; males mature sexually at 1.5–1.7 m (59–67 in) long and females at 2–3 m (79–118 in).[4]

Grey reef sharks are fast-swimming, agile predators that feed primarily on free-swimming bony fishes and cephalopods. Their aggressive demeanor enables them to dominate many other shark species on the reef, despite their moderate size. Many grey reef sharks have a home range on a specific area of the reef, to which they continually return. However, they are social rather than territorial. During the day, these sharks often form groups of five to 20 individuals near coral reef drop-offs, splitting up in the evening as the sharks begin to hunt. Adult females also form groups in very shallow water, where the higher water temperature may accelerate their growth or that of their unborn young. Like other members of its family, the grey reef shark is viviparous, meaning the mother nourishes her embryos through a placental connection. Litters of one to six pups are born every other year.


Founded in 1996, the Reef Check Foundation exists to help preserve the oceans and reefs which are critical to our survival, yet are being destroyed. With headquarters in Los Angeles and volunteer teams in more than 90 countries and territories, Reef Check works to protect tropical coral reefs and California rocky reefs through education, research and conservation.
Off Enewetak, grey reef sharks exhibit different social behaviors on different parts of the reef. Sharks tend to be solitary on shallower reefs and pinnacles. Near reef drop-offs, loose aggregations of five to 20 sharks form in the morning and grow in number throughout the day before dispersing at night. In level areas, sharks form polarized schools (all swimming in the same direction) of around 30 individuals near the sea bottom, arranging themselves parallel to each other or slowly swimming in circles. Most individuals within polarized schools are females, and the formation of these schools has been theorized to relate to mating or pupping.[25][26]
Another danger posed to humans by the Caribbean reef shark involves the accumulation of toxins in the flesh of the shark. Since sharks are apex marine predators, they may contain toxic levels of mercury and other heavy metals due to bioaccumulation (increasing concentrations at higher levels in the food web). It was found that methylmercury levels (MeHg) in sharks off the coast of Florida were higher than the FDA guidelines.
Dutch ichthyologist Pieter Bleeker first described the grey reef shark in 1856 as Carcharias (Prionodon) amblyrhynchos, in the scientific journal Natuurkundig Tijdschrift voor Nederlandsch-Indië. Later authors moved this species to the genus Carcharhinus. The type specimen was a 1.5 metres (4.9 ft)-long female from the Java Sea.[4] Other common names used for this shark around the world include black-vee whaler, bronze whaler, Fowler's whaler shark, graceful shark, graceful whaler shark, grey shark, grey whaler shark, longnose blacktail shark, school shark, and shortnose blacktail shark. Some of these names are also applied to other species.[2]
Based on morphological similarities, Jack Garrick in 1982 grouped this species with the bignose shark (C. altimus) and the sandbar shark (C. plumbeus), while Leonard Compagno in 1988 placed it as the sister species of the grey reef shark (C. amblyrhynchos). A phylogenetic analysis based on allozyme data, published by Gavin Naylor in 1992, indicated that the Caribbean reef shark is the sister taxon to a clade formed by the Galapagos shark (C. galapagensis), dusky shark (C. obscurus), oceanic whitetip shark (C. longimanus), and the blue shark (Prionace glauca). However, more work is required to fully resolve the interrelationships within Carcharhinus.[3]
The "hunch" threat display of the grey reef shark is the most pronounced and well-known agonistic display (a display directed towards competitors or threats) of any shark. Investigations of this behavior have been focused on the reaction of sharks to approaching divers, some of which have culminated in attacks. The display consists of the shark raising its snout, dropping its pectoral fins, arching its back, and curving its body laterally. While holding this posture, the shark swims with a stiff, exaggerated side-to-side motion, sometimes combined with rolls or figure-8 loops. The intensity of the display increases if the shark is more closely approached or if obstacles are blocking its escape routes, such as landmarks or other sharks. If the diver persists, the shark will either retreat or launch a rapid open-mouthed attack, slashing with its upper teeth.[3]

In older literature, the scientific name of this species was often given as C. menisorrah.[5] The blacktail reef shark (C. wheeleri), native to the western Indian Ocean, is now regarded as the same species as the grey reef shark by most authors. It was originally distinguished from the grey reef shark by a white tip on the first dorsal fin, a shorter snout, and one fewer upper tooth row on each side.[6] Based on morphological characters, vertebral counts, and tooth shapes, Garrick (1982) concluded the grey reef shark is most closely related to the silvertip shark (C. albimarginatus).[7] This interpretation was supported by a 1992 allozyme phylogenetic analysis by Lavery.[8]
Blowhole Cliffed coast Coastal biogeomorphology Coastal erosion Concordant coastline Current Cuspate foreland Discordant coastline Emergent coastline Feeder bluff Fetch Flat coast Graded shoreline Headlands and bays Ingression coast Large-scale coastal behaviour Longshore drift Marine regression Marine transgression Raised shoreline Rip current Rocky shore Sea cave Sea foam Shoal Steep coast Submergent coastline Surf break Surf zone Surge channel Swash Undertow Volcanic arc Wave-cut platform Wave shoaling Wind wave Wrack zone
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