HAMMERHEAD SHARK – Sp. Sphyrna
Identification: Hammerhead sharks are unmistakable – for obvious reasons, although identifying exactly which species is another story. Nine species of hammerhead shark occur worldwide, three of which can be found in South African waters. The body of the hammerhead is generally grey-brown dorsally with a lighter underbelly. Fins have no district markings. The eyes are located on flattened lobes each side of the distinctive hammer-shaped head. Teeth on both jaws of the hammerhead shark are relatively small and serrated.
GREAT HAMMERHEAD – Sphyrna mokarran. The body is olive-brown above and lighter below, attaining up to 5.5m. The head is almost rectangular and notched front and center. The first dorsal is very long, elongated and prominent.
SCALLOPED HAMMERHEAD – Sphyrna lewini. The body is greyish above and paler below, attaining up to 4m. The front edge of the head being more noticeably scalloped in shape. The first dorsal is less prominent than that of the great hammerhead.
SMOOTH HAMMERHEAD – Sphyrna zygaena. The body is greyish above and paler below, attaining up to 4m. The front edge of the head being more smoothly convex in shape, lacking the central indentation found in both the scalloped and great hammerheads. The first dorsal is less prominent than that of the great hammerhead and more rounded than on either the scalloped or great hammerhead sharks.
Biology: Sexual maturity is attained at an approx. length of 2m – 2.5m. After about 6 months gestation the young are born live in litters of up to 40 in number. The uniquely shaped and highly sensitive head (swinging from side to side whilst swimming) gives these sharks a wider field of vision than any other shark and also seems a likely tool for detecting and catching prey hidden beneath the sand. Hammerhead sharks have been observed using the head quite literally as a hammer to stun prey. Stingrays, sand sharks, pilchards, anchovies and squid are all important to their diet.
Behavior: Hammerhead sharks are found in all temperate and tropical waters worldwide. All species are thought to be highly migratory. In South Africa adult hammerhead sharks tend to be found visiting offshore reefs like Aliwal Shaol and Protea Banks while juveniles are very common inshore from the Western Cape northwards during summer, often swimming just under the surface. Although relatively shy of divers and notoriously difficult to photograph, large specimens of great hammerhead and schools of several thundered scalloped hammerheads are seasonally encountered by divers on Protea Banks, Often found over the sandy bottoms favored by sand sharks.