There is little information available regarding predators of adult silvertip sharks. Other sharks and large fishes may prey on small or young individuals. Humans present the greatest predatory threat to this species.
Known Predators:
Carcharhinus albimarginatus is named for its shape ("Carcharhinus" from the Greek for "sharp nose) and coloration ("albimarginatus" from the Latin for "white margin").
Silvertip sharks communicate visually, through agonistic displays. Their eyes have a tapetum lucidum structure, enabling them to see in dark murky waters and to see up to 10 times more accurately than humans in clear water. With their lateral lines and Ampullae of Lorenzini, sharks can sense vibrations in the water and electrical fields, alerting them to potential prey, threats, or conspecifics. They have a well-developed sense of hearing as well. In addition, silvertip sharks have a strong sense of smell enabling them to detect small amounts of blood within a large volume of water.
Communication Channels: visual
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical ; electric
Silvertip sharks are catagorized as near-threatened by The International Union for Conservation of Nature and Natural Resources. This is mainly due to fishing pressure associated with pelagic and shelf fisheries (both active and passive, as by-catch) combined with this species' slow growth and reproductive rates.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Following mating, embryos develop within the mother's uterus, nourished by a yolksac placenta, for up to a year. Pups are born in litters of 1-11 and resemble smaller adults (63-68 cm in length, on average). Pups remain in shallow reef areas, moving to deeper waters as they grow. Both males and females reach sexual maturity at 1.6-1.9 meters in length.
Although there have been no attacks on humans recorded in the Global Shark Attack File, these sharks can pose a threat to humans diving near them.
Negative Impacts: injures humans (bites or stings)
Shark meat, teeth and jaws are sold in the areas where they are caught and their fins, skin, and cartilage are also exported for use. Shark flesh can be used fresh or dried and/or salted for human consumption.
Positive Impacts: food ; body parts are source of valuable material
Silvertip sharks are apex predators and often dominate syntopic shark species such as galapagos sharks (Carcharhinus altimus) and blacktip sharks (Carcharhinus amblyrhynchoides). They are host to a number of ectoparasitic copepods. They are followed by pilot fish, and rainbow runners are known to rub against silvertip sharks to dislodge skin parasites.
Commensal/Parasitic Species:
Silvertip sharks are apex predators and consume benthic and mid-water organisms including wahoo (Acanthocybium solandri), spotted eagle rays (Aetobatus narinari), wrasses (Labridae sp.), tuna and bonito (Scombridae sp.), lanternfish (Myctophidae sp.), flyingfish (Exocoetidae sp.), escolar (Gempylidae sp.), bananafish (Albulidae sp.), sole (Soleidae sp.), smaller sharks, octopus, and squid. They tend to be more aggressive feeders than many of the other shark species found in similar habitats and are known to swim at the periphery of groups of feeding sharks, darting in to take food.
Animal Foods: fish; mollusks
Primary Diet: carnivore (Piscivore , Molluscivore )
Silvertip sharks are mainly found in tropical regions of the western Indian Ocean, including the Red Sea and eastern African waters. They are also found in the western Pacific Ocean from southern Japan to northern Australia, including Taiwan, the Philippines and the Solomon Islands, as well as the eastern Pacific from Baja, California to Columbia.
Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); australian (Native ); indian ocean (Native ); pacific ocean (Native )
Other Geographic Terms: holarctic
These pelagic sharks are found both inshore and offshore in tropical waters, often at continental and insular shelves, at depths from the surface to 800 meters. They are also very common around coral banks and reefs, as well as around offshore islands. Juvenile sharks tend to live in more shallow waters to avoid predation.
Range depth: 1 to 800 m.
Habitat Regions: tropical ; saltwater or marine
Aquatic Biomes: pelagic ; reef ; coastal
There is no specific data available regarding the lifespan of silvertip sharks. However, a closely related species (Carcharhinus amblyrhynchos) can live up to 25 years.
Silvertip sharks have a slender, streamlined shape with a long, broadly rounded snout and large, round eyes. The caudal fin is asymmetrical, with a large upper lobe. Additionally, these sharks have two dorsal fins. The first is large and pointed, originating near the same body area as the pectoral fins, and the second dorsal fin is smaller, originating above the anal fin. There are 12-14 serrated teeth in both the lower and upper jaws. General body color is dark gray or gray-brown dorsally, fading to white ventrally. All of the fins have white tips and posterior margins; these are diagnostic characteristic separating these sharks from their closest relatives, gray reef sharks (Carcharhinus amblyrhynchos) and whitetip reef sharks (Carcharhinus albimarginatus). These sharks grow to about 3 meters in length (averaging 2-2.5 meters) and females tend to be larger than males. Maximum recorded weight for a silvertip shark is 162.2 kg.
Range mass: 162.2 (high) kg.
Range length: 2 to 3 m.
Other Physical Features: ectothermic ; bilateral symmetry
Sexual Dimorphism: female larger
Silvertip sharks mate in summer months. Males have paired, symmetrical reproductive structures, known as claspers, located at the edge of the pelvic fins. A male will bite and grasp a female’s tail or body during the mating process and insert a clasper into the female’s cloaca, releasing sperm for internal fertilization. Paired muscular bladders located on the underside of the male's body can use a current of seawater to flush sperm from the female's cloaca, clearing any other males's sperm from her body.
Mating System: polygynandrous (promiscuous)
Silvertip sharks are viviparous; young develop in the mother's uterus, nourished by a yolksac placenta. These sharks breed during the summer months and gestation period is one year, after which 1-11 pups, approximately 63-68 cm long, are born. Males reach sexual maturity upon growing to 1.6-1.8 meters while females reach sexual maturity from 1.6-1.9 meters.
Breeding interval: Silvertip sharks breed once a year.
Breeding season: Breeding season is during the summer.
Range number of offspring: 1 to 11.
Average gestation period: 12 months.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
There is no parental investment from males beyond fertilization. Females carry the gestating young for one year before giving birth; there is no further investment following birth.
Parental Investment: female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female)
The silvertip shark (Carcharhinus albimarginatus) is a large species of requiem shark, in the family Carcharhinidae, with a fragmented distribution throughout the tropical Indian and Pacific Oceans. It is often encountered around offshore islands and coral reefs, and has been known to dive to a depth of 800 m (2,600 ft). The silvertip shark resembles a larger and bulkier grey reef shark (C. amblyrhynchos), but can be easily identified by the prominent white margins on its fins. It attains a maximum length of 3 m (10 ft).
An aggressive, powerful apex predator, the silvertip shark feeds on a wide variety of bony fishes, as well as eagle rays, smaller sharks, and cephalopods. This species dominates other requiem sharks of equal size when competing for food, and larger individuals are often heavily scarred from conflicts with others of its species. As with other members of its family, the silvertip shark is viviparous, with females giving birth to one to 11 pups in the summer. Silvertip sharks are regarded as potentially dangerous to humans, as they often approach divers quite closely. This slow-reproducing species is taken by commercial fisheries for its meat, fins, skin, cartilage, and jaws and teeth, which has apparently led to local population declines or extirpations.
The silvertip shark was originally described as Carcharias albimarginatus by German naturalist Eduard Rüppell, in the 1837 Fische des Rothen Meeres (Fishes of the Red Sea). The name was later changed to the currently valid Carcharhinus albimarginatus.[2] The specific epithet is derived from the Latin albi meaning "white", and marginatus meaning "to enclose with a border",[3] in reference to the distinct white fin margins.[4] In 1960, a 103 cm (3.38 ft)-long immature male caught off Ras Muhammad in the Red Sea was designated as the type specimen.[2] Based on similarities in morphology, tooth shape, and vertebral characters, Garrick (1982) proposed the grey reef shark as the closest relative of the silvertip shark.[5] This interpretation was corroborated by Lavery (1992), based on allozyme data.[6]
The silvertip shark is widely but not continuously distributed in the tropical Indian and Pacific Oceans. In the western Indian Ocean, this species occurs from the Red Sea to South Africa, including Madagascar, the Seychelles, the Aldabra Group, Mauritius and the Chagos Archipelago. In the western Pacific, it is known from off southern Japan to northern Australia, including Taiwan, the Philippines, Indonesia, Papua New Guinea, New Caledonia, Guam, Palau, the Solomon Islands, the Marshall Islands, the Phoenix Islands and Tahiti. In the eastern Pacific, it occurs from southern Baja California to Colombia, including the Cocos, Galapagos, and Revillagigedo Islands. Its presence in the Gulf of Mexico and the Caribbean Sea is unconfirmed.[2]
Silvertip sharks are found over continental and insular shelves at a depth of 30–800 m (98–2,625 ft), occupying all levels of the water column. They are most common around isolated islands, coral banks, and reef drop-offs.[2][7] Juveniles frequent coastal shallows or lagoons, while adults occur in deeper water, with little overlap between the two age groups.[3][8]
The silvertip shark is a robust and streamlined species with a moderately long, broad snout and large, round eyes. The five pairs of gill slits are short. It has 12–14 tooth rows on each side of both jaws, with one or two small teeth at the symphysis (middle of the jaws). The upper teeth are broad with oblique triangular cusps and coarse serrations near the base; the lower teeth have erect cusps with fine serrations. The first dorsal fin is large and triangular, originating above or slightly forward of the free pectoral fin tips. A ridge occurs between the first and second dorsal fins. The pectoral fins are proportionately longer than in most requiem sharks and falcate (sickle-like) in shape, with pointed tips.[2][9]
The coloration is blue-gray above with a bronze sheen, and white below. A subtle white band runs along the sides, with distinctive white tips and borders on all fins. Silvertip sharks can grow up to 3 m (9.8 ft) long, but typically measure 2.0–2.5 m (6.6–8.2 ft) in length. The maximum reported weight is 162.2 kg (358 lb).[3] Females are larger than males.[8]
The silvertip shark can be recognized by its white-edged fins.
Jaws
Upper teeth
Lower teeth
Though silvertip sharks are quite mobile, they exhibit fidelity to certain areas, with reports of territorial behavior. They are usually encountered alone or in pairs.[10][11] Small groups of adult females have been seen in deep water.[8] Individual silvertip sharks behave very aggressively towards one another, and many are heavily scarred. They are also reported to dominate Galapagos sharks (C. galapagensis) and blacktip sharks (C. limbatus) of equal size when competing for food.[2] This shark sometimes forms mixed-species aggregations with grey reef sharks. Rainbow runners (Elagatis bipinnulata) have been observed rubbing against silvertip sharks, using the sharks' rough skin to scrape off parasites.[12] They sometimes follow marine mammals such as bottlenose dolphins (Tursiops sp.) in open water, and are themselves followed by pilot fish (Naucrates ductor).[13]
Like the grey reef shark, the silvertip shark sometimes perform a stereotypical threat display if pursued by divers, warning that it is prepared to attack. The display begins with the shark accelerating away to a distance of 15 m (49 ft), before turning and charging towards the perceived threat. At a distance of two body lengths, the shark brakes, turns broadside, drops its pectoral fins, gapes its jaws, lowers the posterior two-thirds of its body, and "shivers". The last two elements of this display are unique to this species; the "shivering" may serve to emphasize its white fin markings. If the diver persists, the shark may rapidly close in and slash with its upper teeth.[14][15]
The diet of the silvertip shark consists primarily of bony fishes, such as grouper, mackerel, tuna, escolars, lanternfish, flyingfish, wrasses, and soles. Eagle rays, smaller sharks, and octopus are occasionally taken.[2] Larger sharks tend to be more sluggish and take more benthic prey.[13] The differently shaped dentition in their upper and lower jaws allows them to tackle large prey, gripping and sawing off chunks of flesh with violent twists and turns.[8] Silvertip sharks have been observed swimming around the periphery of groups of feeding sharks of other species, occasionally dashing in to steal food.[2] This species often approaches ships, as they are attracted to certain artificial, low-frequency sounds.[16]
Like other requiem sharks, the silvertip shark is viviparous; once the embryos exhaust their supply of yolk, the depleted yolk sac develops into a placental connection through which the mother delivers nourishment. In the Southern Hemisphere, mating and parturition both occur in summer.[16] Courtship involves the male biting the female to hold her for copulation; one female observed had the tip of her first dorsal fin bitten off from such activity.[11] Females bear litters of one to 11 (usually five or six) young after a gestation period of about one year, on a biennial cycle. The newborns have been reported to measure 63–68 cm (25–27 in) and 73–81 cm (29–32 in) long by different authors, and are found in shallower water than adults.[1] The growth rate is highly variable in the wild: Kato and Hernandez (1967) reported juvenile silvertip sharks grow an average of 3.8 cm (1.5 in), or 5.3% of their body length, per year, with some individuals growing as much as 20.8 cm (8.2 in), 30.1% of their body length) per year and others showing negative "growth".[17] Males have been reported to be sexually mature at 1.6–1.8 m (5.2–5.9 ft) or 1.9–2.0 m (6.2–6.6 ft) long, and females at 1.6–2.0 m (5.2–6.6 ft) long.[1]
Inquisitive and bold, especially in the presence of food, the silvertip shark is regarded as potentially dangerous to humans. Often, several sharks will rush up from deep water to inspect divers when they first enter the water, which can be a very intimidating experience, as they may approach quite close.[18][19] This species has also been known to circle or pursue divers.[16] In one experiment involving bait, a large silvertip shark tore the leg off a dummy dressed in SCUBA gear, demonstrating that this species is capable of inflicting lethal injuries.[2] As of 2008, the International Shark Attack File listed four provoked attacks attributable to this species, none of them fatal.[20]
The silvertip shark is caught by commercial and artisan fisheries across its range using longlines, gillnets, and trawls, both intentionally and as bycatch. The fins are highly valued for shark fin soup and are sold on the export market, along with the skin and cartilage. The meat is marketed locally, fresh or dried and salted, as are the jaws and teeth.[1][21] Silvertip sharks are known to be taken by fisheries in Indonesia, Myanmar, and the Philippines, as well as by various Indian Ocean nations with coral reef fisheries; it is also an increasingly important catch of pelagic fisheries, where it is often finned at sea. This species is susceptible to overfishing, due to its slow reproductive rate and tendency to stay in a certain area. It is believed to have been extirpated by Indonesian artisan fishers at Scott Reef off northern Australia, and is likely becoming rare in many other parts of its range. As a result, the International Union for Conservation of Nature has assessed the silvertip shark as vulnerable.[1]
The silvertip shark (Carcharhinus albimarginatus) is a large species of requiem shark, in the family Carcharhinidae, with a fragmented distribution throughout the tropical Indian and Pacific Oceans. It is often encountered around offshore islands and coral reefs, and has been known to dive to a depth of 800 m (2,600 ft). The silvertip shark resembles a larger and bulkier grey reef shark (C. amblyrhynchos), but can be easily identified by the prominent white margins on its fins. It attains a maximum length of 3 m (10 ft).
An aggressive, powerful apex predator, the silvertip shark feeds on a wide variety of bony fishes, as well as eagle rays, smaller sharks, and cephalopods. This species dominates other requiem sharks of equal size when competing for food, and larger individuals are often heavily scarred from conflicts with others of its species. As with other members of its family, the silvertip shark is viviparous, with females giving birth to one to 11 pups in the summer. Silvertip sharks are regarded as potentially dangerous to humans, as they often approach divers quite closely. This slow-reproducing species is taken by commercial fisheries for its meat, fins, skin, cartilage, and jaws and teeth, which has apparently led to local population declines or extirpations.
