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. (Bester, 2012a; Carpenter and Capuli, 2012)
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. (Bester, 2012a; Carpenter and Capuli, 2012)
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. (Bester, 2012a; Carpenter and Capuli, 2012; Compagno, 1984; Ferrari and Ferrari, 2002; McKibben and Nelson, 1986)
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. ("Shark and Ray Reproduction", 2012; Bester, 2012a; Carpenter and Capuli, 2012)
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. ("Shark and Ray Reproduction", 2012; Bester, 2012a)
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. ("Shark and Ray Reproduction", 2012; Bester, 2012a; Compagno, 1984)
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. ("Shark and Ray Reproduction", 2012; Bester, 2012a)
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. (Compagno, 1984; Fitzpatrick, et al., 2011; Martin, 2007; "Shark species involved in incidents", 2005)
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. (Barnett, et al., 2012; Pilans, et al., 2012)
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. (Guttridge, et al., 2009; Martin, 2007)
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. (Bester, 2012a; Compagno, 1984)
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. (Bester, 2012a; Pilans, et al., 2012)
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. ("Shark and Ray Reproduction", 2012; Bailly, 2013; Bright, 2000; Compagno, 1984; Fitzpatrick, et al., 2011; Guttridge, et al., 2009; Martin, 2007; McKibben and Nelson, 1986)
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. (Camhi, et al., 2007)
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. (Martin, 2007; "Shark species involved in incidents", 2005)
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. (Camhi, et al., 2007; Pilans, et al., 2012)
Michael Hsieh (author), The College of New Jersey, Matthew Wund (editor), The College of New Jersey, Jeremy Wright (editor), University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
active at dawn and dusk
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
uses electric signals to communicate
parental care is carried out by females
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
Found in northern North America and northern Europe or Asia.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
found in the oriental region of the world. In other words, India and southeast Asia.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
an animal that mainly eats fish
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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Bester, C. 2012. "Grey Reef Shark" (On-line). Ichthyology at the Florida Museum of Natural History. Accessed February 20, 2013 at http://www.flmnh.ufl.edu/fish/Gallery/Descript/GReefShark/GReefShark.html.
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Bright, M. 2000. The Private Life of Sharks: The Truth Behind the Myth. Mechanicsburg, PA: Stackpole Books.
Camhi, M., S. Valenti, S. Fordham, S. Fowler, C. Gibson. 2007. Conservation Status of Pelagic Sharks and Rays. Report of the IUCN Shark Specialist Group Pelagic Shark Red List Workshop, 1: 19-23. Accessed February 20, 2013 at http://cmsdata.iucn.org/downloads/ssg_pelagic_report_final.pdf.
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Guttridge, T., A. Myrberg, I. Porcher, D. Sims, J. Krause. 2009. The role of learning in shark behaviour. Fish and Fisheries, 10/ 4: 450-469.
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Pilans, R., E. Medina, N. Dulvy. 2012. "Carcharhinus albimarginatus" (On-line). IUCN Red List of Threatened Species. Accessed February 20, 2013 at http://www.iucnredlist.org/details/full/161526/0.