Sphyrnidae

Scalloped hammerhead

Sphyrna lewini

Hundreds of hammers moving poleward in summer

• Blue
• Gray
• White
• Tropical
• Nearshore
• Globally widespread
• Marine fish
• Fusiform
• Large
• Tropical fish

Celebrated for forming colossal daytime schooling aggregations around oceanic pinnacles, the scalloped hammerhead is an iconic, highly migratory pelagic shark of tropical waters. Its broad cephalofoil displays a deeply arched anterior outline marked by a distinct central indentation and two lateral notches resembling a scalloped seashell. Shaded in bronze, olive, or grey-brown above and pale white below, it possesses long, swept-back pectoral fins with dark-tipped undersides. Circumglobally distributed through warm temperate and tropical coastal waters down to five hundred meters depth, schools numbering in the hundreds congregate diurnally around offshore volcanic seamounts and current-swept island drop-offs. At dusk, the vast school disperses offshore into deep oceanic trenches, where individuals use acute electromagnetic sensors to hunt pelagic squid, mackerel, sardines, and bottom-dwelling rays. Viviparous with litters up to forty pups, this species attains recorded maximum total lengths of four hundred and thirty centimetres.

Sources: NOAA Fisheries — Scalloped Hammerhead Shark, Sphyrna lewini