The most commonly encountered reef shark in the Caribbean Sea is the Caribbean Reef Shark (Carcharhinus perezi). This shark also occurs in the tropical waters of the western Atlantic Ocean.
The Caribbean reef shark is a requiem shark species from the family Carcharhinidae. Members of this family have a typically robust and streamlined body. Thus, it is not very easy to tell this species apart from other large members of its family.
This shark is one of the largest apex predators in the reef ecosystem reaching up to 9.8 feet (3 m) in length. They have amazing display features, active swimming, and unusual resting behavior.
Distinguishing the Caribbean Reef Shark from Other Large Carcharhinids
The Caribbean reef shark looks especially like other members of its family such as the silky shark (C. falciformis) and the dusky shark (C. obscurus). Differentiating this shark are the dusky-colored fins lacking prominent markings, tooth number and shape, and a short free rear tip found on the second dorsal fin.
Interrelationship and Scientific Classification
Felipe Poey at first described this species as Platypodon perezi in 1876. This description came in a scientific journal Anales de la Sociedad Española de Historia Natural. The type specimens used were six individuals caught off the coast of Cuba. Later authors synonymized the genus Platypodon with Carcharhinus.
Jack Garrick in 1982, considered the form and structure (morphology) of Caribbean reef sharks, then grouped them with the bignose shark (C. altimus) and the sandbar shark (C. plumbeus). In 1988, Leonard Compagno named this species sister to the grey reef shark (Carcharhinus amblyrhynchos).
Further, in 1992, research on the evolutionary history (phylogeny) of this species by Gavin Naylor showed that the Caribbean reef shark is sister to the clade which includes the Galapagos shark (C. galapagensis), oceanic whitetip shark (C. longimanus), dusky shark (C. obscurus), and the blue shark (Prionace glauca).
Identifying a Caribbean Reef Shark
The Caribbean shark is a large shark with a typical requiem shark body shape. This shark has a rather short, broad, and rounded snout that lacks the prominent flaps of skin by the nostrils. The eyes are large with a circular shape and have protective third eyelids (nictitating membrane). This shark has five pairs of gill slits that are moderately long. The third-gill slit is situated over the origin of the pectoral fins.
Dentition
Either half of both the upper and the lower jaws have 11 – 13 tooth rows. The teeth have narrow cusps, serrated edges, and broad bases. Apart from the first 2 – 4 teeth on each side which are erect, the others tend to have increasingly oblique shape.
Dermal Denticles
The dermal denticles covering the body of the Caribbean Reef Shark overlap with very close spacing. Every 5 – 7 horizontal low ridges of each denticle lead to marginal teeth.
Fins
The first dorsal fin extends high with the shape of a sickle. Then, between the first and the second dorsal fin is a low interdorsal ridge. The second dorsal fin is relatively large and has a short free rear tip. Originating over or slightly forward of the free rear tips of the pectoral fins is the first dorsal fin. While the second dorsal fin originates over the anal fin or slightly forward.
This shark’s pectoral fins taper to a point. They are narrow and long. The upper lobe of the caudal fin is larger than the lower lobe.
Coloration
The backside (dorsal) of the Caribbean reef shark has a dark gray gray-brown color. While the underside (ventral) is white in color or sometimes white-yellow. There are not quite visible white bands on the flanks. The undersides of the paired fins are dusky. This is the same with the lower lobe of the caudal fin and the anal fin. However, the fins, in general, do not have any prominent markings.
Size and Weight
The Caribbean reef shark has an average length of 6.6 to 8.2 feet (2.0 to 2.5 m). Though, the maximum length recorded is 9.8 feet (3 m). And, this shark has been reported at a maximum weight of 150 lb (70 kg).
Where to Find Caribbean Reef Sharks
This shark species prefers shallow waters of coral reefs and the surrounding. Often, these sharks swim to the outer edges of the reef, near the drop-offs. They would commonly choose water depths of 98 feet (30 m) or shallower. Although, they can dive as deep as 1,240 feet (378 m).
The Caribbean reef shark inhabits the waters of the western Atlantic Ocean. They occur as far north as North Carolina and as far south as Brazil. As a result, the range of distribution includes the Caribbean sea, Bermuda, and the northern Gulf of Mexico. In all, this shark is very rare north of Florida keys.
Typical Behavior
Caribbean reef sharks are active shark species, however, they tend to show increased activity at night. Of all studies on this species, there is no evidence of migration or changes in activity attributed to season. In fact, as juveniles, these sharks stay within a localized area throughout the year. And, adults occupy a wider area.
Despite their level of activity, Caribbean reef sharks still sometimes rest motionless in caves or on reef floors. This makes them the first active shark species with reports of such behaviors. More so, there was an investigation in 1975, by Eugenie Clark on the famous “sleeping shark”. This took place at Isla Mujeres off the Yucatan Peninsula inside the caves. The result showed that these sharks were not actually sleeping because their eyes would follow divers even while they are motionless.
Clark then suggested that the upwelling of fresh water inside the caves may loosen parasites attaching on the shark, while also producing an enjoyable “narcotic effect”. Thus, the shark feels lethargic.
Threat Display
When threatened, these sharks may perform a threat display. This involves them swimming in a short, jerky manner while repeatedly dropping the pectoral fins in about one-second intervals and changing directions frequently. However, their display is not as pronounced as that of the grey reef shark (Carcharhinus amblyrhynchos).
Hunting Techniques
The Caribbean reef shark is responsive to low frequency sounds underwater. This sound is an indication of a struggling fish. During an observation of a male Caribbean reef shark measuring 6.6 feet (2.0 m), hunting a yellowtail snapper (Lutjanus crysurus), the shark first displayed a sluggish circling and several turns lacking spirit toward its prey. All of a sudden, its speed increased and by swinging the head sideways, it caught the snapper by the corner of its jaws.
Food Preferences
The choice of food of the Caribbean reef shark includes bony fishes, cephalopods, and some elasmobranchs such as yellow stingrays (Urobatis jamaicensis) and eagle rays (Aetobatus narinari). Juvenile Caribbean reef sharks feed mainly small fishes, crabs, and shrimps.
This shark species can avert the content of its stomach. It likely adopts this practice as a cleansing process, thus, removing undigested food, mucus, and parasites from the lining of the stomach.
Caribbean Reef Sharks Predators and Parasites
Larger sharks such as bull shark (Carcharhinus leucas), and the tiger shark (Galeocerdo cuvier) prey upon juvenile Caribbean reef sharks.
The parasites of this species are few and include a leech with discreet markings of various colors hanging down from the shark’s first dorsal fin. Juveniles off northern Brazil seek out areas occupied by yellownose gobies (Elacatinus randalli) as cleaning stations. Consequently, these cleanse the sharks of their parasites as they lie motionless on the bottom.
Fishes such as bar jacks (Carangoides ruber) and horse-eye jacks (Caranx latus) school around Caribbean reef sharks regularly.
Mating and Reproduction
The bite marks found on female Caribbean reef sharks show that these sharks engage in an aggressive mating ritual. Reproduction is viviparous, and this involves sustaining the developing embryos through a yolk sac which upon the exhaustion of yolk, transforms into a placental connection that connects the embryos to the mother for nourishment.
The birthing of the young ones can take place at different times in different locations. As such, these species give birth from February to April during the end of the dry season at the Fernando de Noronha Archipelago and Atol das Rocas off Brazil. However, they give birth in November and December during the amazon summer at other locations in the southern hemisphere.
Gestation in this species lasts for one year. An average litter contains 4 to 6 pups. At birth, the pups measure about 29 inches (74cm) in length. Sexual maturity occurs in males at the size of 59 to 67 inches (1.5 to 1.7 m). While the females mature at 79 to 118 inches (2 to 3 m).
Caribbean Reef Sharks and Humans
Danger to Humans
Caribbean reef sharks can be considered potentially dangerous to humans. They grow large enough and are aggressive in the presence of food, hence can cause harm. Although, encounters with divers show that these sharks are rather indifferent or shy in their presence.
Attacks on Humans
The International Shark Attack File (ISAF) as of 2008, listed 27 attacks on humans attributed to this species. Only but 4 out of these attacks were unprovoked. However, none was fatal. Caribbean reef sharks are more likely to attack in spring and summer.
Importance to Humans
Throughout the range of habitat of Caribbean reef sharks, commercial and artisanal longline and gillnet fisheries take them for various purposes. For example, its value includes the provision of meat, liver oil, leather, and fishmeal.
In Colombia, the Caribbean reef shark is a common catch with about 39% longline catch by occurrence. Here, it is most important for its fins, oils, and jaws which can serve ornamental purposes.
In Belize, this species often come as a bycatch on hook-and-line meant for snappers and groupers. The local people of Belize, Mexico, and Guatemala make panadas (a confection just like a tortilla) out of the meat while selling the fins to the profitable Asian market.
Above all, it is worthy to note that the flesh of Caribbean reef sharks may contain methylmercury and other heavy metals.
Shark Feeding
Shark feeding is a human interaction with sharks which involves organized feeding of groups of reef sharks attracted by baits toward divers. It is a profitable ecotourism industry revolving around the Caribbean reef shark species. This practice tends to draw controversy as proponent groups state that shark feeding contributes to conservation by working as an incentive to shark protection and educating people about the sharks.
However, opponents argue that these sharks may get used to human foods, thereby increasing the rate of attacks on humans. Also, they hinted at the removal of reef fishes for baits as possible damage to the local ecosystem.
Off the Coast of Florida, the practice of shark feeding has been outlawed. However, at other locations in the Caribbean, this practice continues.
Conservation Status
The International Union for Conservation of Nature (IUCN) listed the Caribbean reef shark as a “Near Threatened (NT)” species. This assessment is a result of the decline in the population of this species in Cuba and off Belize due to overfishing. And also, the continued exploitation in other regions.
Threat to Population
The major threat to the population of Caribbean reef sharks includes human exploitation and overfishing. Others are destruction and degradation of the coral reefs in which they inhabit.
Conservation Actions
Various conservation actions are being put in place to protect this species. For example, fishing of this species in the United States waters is prohibited. In the Bahamas, Caribbean reef sharks are under protection due to their importance in ecotourism. Other places include Marine Protected Areas (MPAs) off Brazil and other areas.
This shark species is still vulnerable due to the lack of enforcement in some reserves. Moreover, many places where this species is abundant does not have any form of protection.
Amazing Caribbean Reef Shark Facts at a Glance
1. Among the Largest Apex Predators in the Reef Ecosystem
With a size of up to 9.8 feet (3.0 m), the Caribbean reef shark is one of the largest apex predators feeding mainly on bony fishes and cephalopods.
2. Unusual Resting Behavior for an Active Species
These sharks lie motionless inside caves or reef bottoms. Of course, this is unusual for a shark with a high activity level. Thus, the Caribbean reef shark is the first active shark species with such behavior.
3. Exhibits Threat Display
Although not pronounced as that of the grey reef shark (C. amblyrhynchos), Caribbean reef sharks display specific motion if threatened. This involves constant changing of directions and dipping of the pectoral fins.
4. Potentially Dangerous to Humans
The structure and build of the Caribbean reef shark
show it can cause quite a damage if it attacks. However, these sharks are unlikely to attack humans as they show little or no interest in divers. Only a few attacks on humans by this species are on record. Most are provoked attacks, but none is fatal.
5. Shows Preference to Shallow Waters
These sharks are common in depths shallower than 98 feet (30 m). Though, they can dive deeper than this at times.
6. Difficult to Distinguish from Other Large Requiem Sharks
Due to the body shape typical to requiem sharks, the Caribbean reef shark is difficult to tell apart from other large members of its family such as the silky shark (C. falciformis) and the dusky shark (C. obscurus).
7. Valued as an Ecotourist Attraction
This shark species is popular in the controversial “shark feeding” practice where baits are used to attract them to groups of divers.
8. The Existence of Interdorsal Ridge between the First and the Second Dorsal Fins
A low interdorsal ridge runs behind the first dorsal fin to the second dorsal fin.
9. Juveniles Occupy a More Localized Area Throughout the Year
The juvenile Caribbean reef shark would remain in a localized area in a year, while adults choose a wider area.
10. They are not Migratory Species
Caribbean reef sharks have no evidence of seasonal migration or behavioral changes.
11. Capable of Everting Their Stomachs
Caribbean reef sharks will evert their stomachs probably to cleanse parasites, indigestible particles, and mucus from the lining of their stomach.
12. Human Activities are the Major Threats of Caribbean Reef Sharks
Activities of man such as overfishing and coral reef habitat degradation due to development lead to the loss population of this species. Hence, currently assessed as “Near Threatened”.
Further Reading
- “Carcharhinus perezi, Caribbean reef shark”, Fish Base.
- “Discover Fishes: Carcharhinus perezi – Caribbean Reef Shark”, Florida Museum of Natural History.
- “Carcharhinus perezi“, IUCN Red List of Threatened Species.
- “Caribbean Reef Shark”, wikipedia (accessed April 4, 2020).