Silvertip shark - Carcharhinus albimarginatus

General body structure

The silvertip shark Carcharhinus albimarginatus has a robust, fusiform body. The body shape is adapted for powerful, sustained swimming in open water. The trunk is muscular, with a nearly circular cross-section. Adults typically reach 2 to 2.5 metres in length, though some individuals grow larger.

The dorsal colouration ranges from grey-brown to bronze. The underside is noticeably lighter. The conspicuous white tips on all fins are characteristic. This marking gives the species its name and serves as an important identification feature.

Head and snout shape

The head is broad with a relatively short, bluntly rounded snout. The eyes are medium-sized and possess a nictitating membrane. This protective membrane can cover the eye during biting motions.

The nostrils are located on the underside of the snout and are equipped with skin flaps that direct the water flow over the olfactory receptors. Like other species of the genus Carcharhinus, the silvertip shark has five gill slits on each side.

Dentition and tooth morphology

The dentition is heterodont. The upper and lower jaws bear differently shaped teeth.

• Upper teeth are broad, triangular and distinctly serrated.
• Lower teeth are narrower, more pointed and also serrated.

This tooth structure allows both gripping and tearing off larger prey. The tooth rows are continuously replaced. Several replacement rows lie behind the functional tooth row.

Fin morphology

The first dorsal fin is large, sickle-shaped and begins roughly above the rear base of the pectoral fins. The second dorsal fin is considerably smaller, but relatively well developed in proportion to body size.

The pectoral fins are long and falcate in shape. Their form stabilises buoyancy and enables controlled changes of direction. The pelvic fins are medium-sized. The anal fin is small but functionally stabilising.

The caudal fin is asymmetrical. The upper lobe is greatly elongated. This heterocercal tail shape generates thrust while also producing slight lift, since sharks lack a swim bladder.

Skin structure and dermal denticles

The skin is covered with placoid scales, also called dermal denticles. These microscopic structures have a serrated surface. They reduce drag and improve the flow along the body.

The surface structure of the denticles also provides protection against parasites and mechanical injury. Studies on hydrodynamic optimisation in sharks show that such skin structures measurably improve energy efficiency during swimming.

Sensory organs

Ampullae of Lorenzini

Like all modern sharks, the silvertip shark also possesses a well-developed electroreceptive system. The ampullae of Lorenzini are gel-filled canals in the head region. They detect weak electric fields produced by the muscular activity of other animals.

Lateral line organ

The lateral line runs along the sides of the body. It responds to pressure changes and water movements. This system allows detection of movements even when visibility is poor.

Sense of smell

The olfactory organ is highly developed. Water continuously flows over folded olfactory lamellae. Odours are detected even at very low concentrations.

Skeleton and musculature

The internal skeleton is composed of cartilage. Cartilage is lighter and more flexible than bone. This structure reduces body weight and increases manoeuvrability.

The musculature is segmented. Much of it consists of red muscle for sustained swimming. White muscle enables rapid accelerations. This combination is typical of active pelagic sharks.

Distinction from similar species

The white fin tips clearly distinguish the silvertip shark from the grey reef shark (Carcharhinus amblyrhynchos). In the grey reef shark, the fin margins are darker. The silvertip shark’s body proportions also appear more robust.

The combination of a robust body, large sickle-shaped fins and striking white tips makes Carcharhinus albimarginatus anatomically unmistakable.

Overview of functional adaptations

Feature	Function
Spindle-shaped body	Reduced water resistance
Large first dorsal fin	Stabilisation during rapid turns
White fin tips	Species-specific trait for visual identification
Dermal denticles	Hydrodynamic optimisation and protection
Heterocercal tail fin	Propulsion and lift compensation

The body structure of the silvertip shark is consistently geared towards active, powerful locomotion and precise sensory perception. Anatomy and external features form a functional unit that clearly characterises this species within the genus.

Geographical distribution in the Indo-Pacific

The silvertip shark Carcharhinus albimarginatus is widespread in the tropical Indo-Pacific. Its range extends from the east coast of Africa across the Red Sea to the western and central Pacific. Records exist, among others, from waters off South Africa, Mozambique, Madagascar and the Seychelles.

In the Indian Ocean, the species occurs around island groups such as the Maldives and the Andaman Islands. In the western Pacific the range extends from Indonesia and Papua New Guinea through the Philippines to northern Australia. Confirmed records have also been reported from Micronesia, Melanesia and Polynesia. In the central Pacific the species is regularly recorded at isolated oceanic islands.

The distribution is wide-ranging but not uniform. Local populations are primarily concentrated on structurally complex reef systems and remote island regions with limited coastal development.

Preferred habitats

Coral reefs and reef edges

The silvertip shark is closely associated with tropical coral reefs. It uses outer reefs, reef drop-offs and steeply sloping reef edges. It is especially common at exposed sites with stronger currents. These areas provide stable environmental conditions and a high density of reef organisms.

Studies in Indo-Pacific protected areas show that the species occurs primarily on healthy, structurally complex reefs. Heavily degraded or overfished reefs have markedly lower sighting rates.

Ocean islands and atolls

Isolated oceanic islands and atolls constitute important habitats. There, the species is found along steep island slopes and on underwater plateaus. Satellite tagging from the western Indian Ocean shows that individual animals remain near particular island groups for extended periods and travel only limited distances.

This site fidelity suggests a close association with specific reef structures. At the same time, occasional movements between neighbouring reef systems have been documented.

Depth range

The silvertip shark predominantly occupies the upper part of the water column. Most observations come from depths between 0 and 100 metres. However, it can also occur at much greater depths. Scientific records report maximum depths of over 800 metres, although such values are rare and usually based on single observations.

Near the coast, the species prefers clear, warm waters. Turbid estuarine areas or heavily sediment-laden coastal sections are avoided.

Ecological conditions

This species is typical of tropical water temperatures. Its habitat is usually in regions with stable temperatures above 22 degrees Celsius. Coral reefs with high structural complexity provide refuges and hunting grounds.

Studies from marine protected areas such as the Chagos Archipelago show that high individual densities occur mainly in lightly fished areas. There, the silvertip shark is one of the dominant larger shark species associated with reef systems. In heavily exploited coastal regions, however, it has become rare.

Distinction from nearshore and pelagic habitats

Compared with strictly coastal species, the silvertip shark avoids shallow lagoons and heavily influenced coastal zones. At the same time, it is less pelagic than oceanic high-seas species. Its habitat is mainly in the transition zone between reef and open sea.

This reliance on reef structures makes the species particularly dependent on intact coral ecosystems. Changes caused by climate change, coral bleaching or intensive fishing directly affect its habitats.

Behaviour

The silvertip shark is one of the active offshore reef sharks of tropical seas. It primarily uses outer reef edges, steep drop-offs and nearshore ocean areas. There it patrols at mid-water depths and regularly moves between coastal structures and open water.

It is regarded as a powerful, confident predator. Diver observations show a direct approach towards potential prey. Instead of being a site-faithful bottom-dwelling shark, it is a mobile predator with a large range. Telemetry studies from the Indo-Pacific show that individual animals can travel several dozen kilometres within a few days.

Juveniles are more frequently found in sheltered, shallower areas. Adults dominate exposed reef zones. Social behaviour is loosely structured. Temporary loose groups form, especially where prey is concentrated.

Activity patterns

The silvertip shark is predominantly crepuscular and nocturnal. During these periods activity and hunting success increase markedly. By day it moves more quietly along reef edges or near underwater plateaus.

Feeding and hunting strategy

Carcharhinus albimarginatus feeds mainly on bony fishes. These include reef fishes such as groupers, mackerels or smaller tunas. Cephalopods such as squid are also part of its diet. Occasionally smaller sharks and rays are taken.

Hunting is usually active and fast. The silvertip shark uses its high acceleration to scatter shoals. Individual prey are purposefully chased. Its keen sense of smell and electroreceptive system help locate injured or hidden prey.

Role in the ecosystem

As a large reef predator, the silvertip shark regulates populations of medium-sized fishes. Studies on remote coral reefs in the Indian Ocean show that its presence is associated with a stable structure of higher trophic levels. In its absence, the composition and behaviour of many reef fishes change measurably.

Reproduction

The silvertip shark is viviparous. The embryos develop in the uterus and are supplied via a yolk-sac placenta. This reproductive system is typical for many species of the genus Carcharhinus.

Gestation period and litter size

Gestation lasts about twelve months. A litter usually comprises one to eleven pups. Newborns measure approximately 60 to 70 centimetres. Females probably give birth to their young in coastal areas with lower predation pressure.

Sexual maturity and reproductive rate

Sexual maturity is reached relatively late. Males are reproductive at around 1.6 to 1.8 metres in length. Females typically mature at somewhat larger sizes. The comparatively small litter size and the long gestation lead to a low reproductive rate. Populations are therefore sensitive to increased mortality.

Long-term observations suggest that females do not become pregnant every year. There can be resting periods between two litters. This strategy increases the mother’s chances of survival but markedly slows population growth.

Current conservation status

The Silvertip shark (Carcharhinus albimarginatus) is classified by the International Union for Conservation of Nature as Vulnerable. This category indicates an increased risk in the wild. The assessment is based on documented population declines in several parts of the Indian Ocean and the western Pacific, as well as sustained high fishing pressure.

The global population trend is considered to be decreasing. Regional data show marked declines in heavily fished coastal areas. Robust global population figures are difficult to obtain because many catch statistics do not record sharks by species.

Primary causes of threat

Industrial and artisanal fisheries

The Silvertip shark is both targeted and taken as bycatch. Longlines and nets are mainly used. Fins are of particular economic importance and fetch high prices on the international market. Meat and skin are also marketed. In many regions there is no effective control of catch volumes.

The species often inhabits coastal waters and reef structures. These habitats overlap with intensive fishing, so the likelihood of capture is high.

Biological vulnerability

The Silvertip shark has a comparatively low reproductive rate. Gestation is long and the number of pups per litter is limited. Populations therefore respond sensitively to increased mortality; a strong decline can only be offset slowly.

Habitat loss

Coral reefs and nearshore coastal ecosystems are under pressure worldwide. Causes include overfishing, coastal development and climate-related coral bleaching. Because the silvertip shark is closely tied to such habitats, changes to them directly affect its populations.

International conservation measures

CITES regulation

The silvertip shark is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES). International trade in products of this species is therefore subject to permits. Exports may only be allowed if it can be scientifically demonstrated that they do not endanger the populations. This regulation is intended mainly to restrict the global fin trade.

Regional fisheries management systems

Several regional fisheries organisations have introduced regulations to reduce shark catches. These include fishing bans in certain areas, reporting requirements and measures against the removal of fins at sea. Implementation and enforcement, however, vary greatly between countries.

Marine protected areas

In some countries silvertip sharks benefit from large protected areas where commercial fishing is restricted or prohibited. Such areas can help stabilise local populations. Movements beyond protected-area boundaries remain a problem.

Assessment of conservation status

The combination of high demand for shark products and biological vulnerability poses an ongoing risk to the species. International trade controls are an important step, but they do not replace effective monitoring of fisheries at the national level. In many regions reliable data on population trends are lacking.

The long-term protection of the silvertip shark depends on consistent catch regulation, transparent data collection and the protection of sensitive reef ecosystems.