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The Scalloped Hammerhead (Sphyrna lewini) is a large species of hammerhead shark, characterized by its distinctive 'scalloped' or indented anterior margin of the cephalofoil (hammer-shaped head). It is a highly migratory, pelagic species found in warm temperate and tropical waters worldwide. Known for forming large schools, especially juveniles, it plays a crucial role as an apex predator in marine ecosystems. Its unique head structure is believed to enhance sensory capabilities, aiding in prey detection.
Physical Characteristics
- Body shape
- torpedo
- Coloration
- Dorsally dark bronze to olive-brown, fading to white or off-white ventrally. Fins may have dusky tips, especially in juveniles.
- Scale type
- placoid
- Mouth position
- inferior
- Distinctive features
- Cephalofoil (hammer-shaped head) with a distinct indentation or 'scallop' in the center of the anterior margin., Relatively small mouth compared to other large sharks., First dorsal fin is tall and falcate (sickle-shaped), originating over or slightly behind the pectoral fin axil., Second dorsal fin is relatively high with a deeply notched posterior margin., Pectoral fins are moderately long and falcate.
- Dorsal fin
- Two dorsal fins. The first is tall, falcate, and originates over or slightly behind the pectoral fin axil. The second is smaller but relatively high with a deeply notched posterior margin.
- Tail fin
- Heterocercal caudal fin; upper lobe is significantly longer than the lower lobe, with a distinct subterminal notch.
- Pectoral fin
- Moderately long and falcate.
- Distinctive fins
- The cephalofoil is the most distinctive feature, with a central indentation on its leading edge.
Identification Tips
Cephalofoil Shape
Look for the distinct central indentation or 'scallop' on the leading edge of the hammer-shaped head. This is the primary distinguishing feature from other hammerhead species.
First Dorsal Fin Origin
The origin of the first dorsal fin is typically over or slightly behind the pectoral fin axil. This helps differentiate it from the Great Hammerhead (Sphyrna mokarran) where the first dorsal fin originates over the pectoral fin insertion.
Second Dorsal Fin
The second dorsal fin is relatively tall with a deeply notched posterior margin, which is more pronounced than in some other hammerhead species.
Body Coloration
Generally bronze to olive-brown dorsally, fading to white ventrally. This coloration can be a general indicator but is not definitive on its own.
Habitat
- Water type
- saltwater
- Depth
- Primarily epipelagic and coastal, ranging from the surface down to at least 500 meters (1,640 feet). Often found near continental and insular shelves, and in offshore waters.
- Environment
- Coastal and oceanic waters, often associated with coral reefs, estuaries, and open ocean. Juveniles utilize shallow, protected coastal areas as nurseries.
- Geographic range
- Circumglobal in tropical and warm temperate oceans, between latitudes 40°N and 40°S. Found in the Atlantic, Pacific, and Indian Oceans.
Aquarium Information
- Care level: expert
- Temperament: aggressive
- Diet: carnivore
- Minimum tank size: Not suitable for home aquaria; requires extremely large public aquarium facilities.
- Temperature: 22-28°C (72-82°F)
- pH level: 8.1-8.4
- Hardness: High (marine salinity)
- Compatibility: Only compatible with very large, robust marine species in public aquaria, and typically kept in species-specific exhibits due to their size and predatory nature.
- Special requirements: Requires immense tank volume, strong filtration, specialized feeding protocols, and expert husbandry. Not suitable for private aquarists.
Wild Information
- Conservation status: critically endangered
- Seasonality: Highly migratory; seasonal movements are influenced by water temperature, prey availability, and reproductive cycles. Juveniles often aggregate in coastal nurseries during warmer months.
- Market price: Variable, often high for fins in illegal markets; meat value is lower.
- Commercial importance: high
- Taste: Strong, gamey flavor, often described as 'fishy'.
- Texture: Firm, meaty.
- Cooking methods: Grilled, Fried, Smoked, Curried
- Nutritional value: Good source of protein, but can accumulate high levels of mercury and other heavy metals, making consumption risky.
Key Facts
Sensory Advantagebehavior
The unique shape of the hammerhead's cephalofoil is believed to provide a larger surface area for electroreceptors (ampullae of Lorenzini), enhancing their ability to detect the electrical fields of prey buried in the sand.
Schooling Behaviorbehavior
Juvenile Scalloped Hammerheads are known to form massive schools, sometimes numbering in the hundreds or even thousands, in coastal nursery areas. This schooling behavior is thought to offer protection from predators and aid in social learning.
Global Migrationsbehavior
Scalloped Hammerheads undertake extensive migrations, often covering thousands of kilometers, between feeding grounds, breeding areas, and nursery habitats.
Critically Endangered Statusinteresting
Due to overfishing, particularly for their fins in the shark fin trade, and habitat degradation, the Scalloped Hammerhead is listed as Critically Endangered by the IUCN Red List.
Viviparous Reproductionbehavior
Scalloped Hammerheads are viviparous, meaning they give birth to live young. Females have a gestation period of 9-12 months and can produce litters of 15-31 pups.
Safety Information
Handle with care- Safety level: caution
- Venomous: No
- Edibility: not recommended
- Handling notes: Scalloped Hammerheads are large, powerful predators. While not typically aggressive towards humans, they are wild animals and should be treated with respect and caution. Avoid provoking them, especially if encountered in the water. Anglers should exercise extreme care when handling, as their size and strength can be dangerous. Release should be done quickly and with minimal stress to the animal, using appropriate de-hooking tools.
Similar Species
Great Hammerhead
Sphyrna mokarran
The Great Hammerhead has a straight or slightly arched anterior margin of the cephalofoil, lacking the central indentation seen in the Scalloped Hammerhead. Its first dorsal fin is also taller and originates further forward, over the pectoral fin insertion.
Smooth Hammerhead
Sphyrna zygaena
The Smooth Hammerhead has a smoothly arched anterior margin of the cephalofoil without any indentation. Its first dorsal fin is also less falcate and originates further back than in the Scalloped Hammerhead.
Bonnethead Shark
Sphyrna tiburo
The Bonnethead is a much smaller species with a shovel-shaped cephalofoil that is broadly rounded, not hammer-shaped with distinct lobes. It is easily distinguished by its size and head morphology.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Chondrichthyes
- Order
- Carcharhiniformes
- Family
- Sphyrnidae
- Genus
- Sphyrna
- Species
- Sphyrna lewini
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