Carcharhinus albimarginatus

Geographic Range

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 nearctic
  • native native
• palearctic palearctic
  • native native
• oriental oriental
  • native native
• ethiopian ethiopian
  • native native
• neotropical neotropical
  • native native
• australian australian
  • native native
• indian ocean
  • native native
• pacific ocean pacific ocean
  • native native

• Other Geographic Terms
• holarctic holarctic

Habitat

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.

• Habitat Regions
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• pelagic pelagic
• reef reef
• coastal coastal

Physical Description

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 ( Triaenodon obesus ). 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.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Development

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.

Reproduction

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) 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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• viviparous 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 female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

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.

Behavior

Silvertip sharks display agonistic behavior, engaging against potential threats with stereotyped display movements. These include lowering the angles of the pectoral and tail fins, stiff or jerky movements without locomotion, "shivering," opening the jaws wide, and making quick movements away from the potential threat. Should the threat persist, the shark typically either withdraws or attacks quickly. Although not considered territorial, silvertip sharks will attack members of their own species if threatened and often have combat scars on their bodies. Although there are no Global Shark Attack Record files for this species, they are known to be aggressive to humans perceived as threats.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• solitary solitary

Home Range

These sharks are typically solitary and their populations are fragmented, with little to no interchange between them. Although they can be aggressive when threatened, there is no evidence that they maintain specific territories or home ranges.

Communication and Perception

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 visual

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical
• electric electric

Food Habits

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.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • molluscivore molluscivore

• Animal Foods
• fish
• mollusks

Predation

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.

Ecosystem Roles

Silvertip sharks are apex predators and often dominate syntopic shark species such as galapagos sharks ( Carcharhinus galapagensis ) and blacktip sharks ( Carcharhinus limbatus ). 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.

Economic Importance for Humans: Positive

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 food
• body parts are source of valuable material

Economic Importance for Humans: Negative

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

Conservation Status

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.

Other Comments

Carcharhinus albimarginatus is named for its shape ("Carcharhinus" from the Greek for "sharp nose) and coloration ("albimarginatus" from the Latin for "white margin").

Additional Links

Encyclopedia of Life

Contributors

Michael Hsieh (author), The College of New Jersey, Matthew Wund (editor), The College of New Jersey, Jeremy Wright (editor), University of Michigan-Ann Arbor.

References

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