GREAT HAMMERHEAD

 

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Common Names: Great Hammerhead

Latin Name: Sphyrna Mokarran

Family: Sphyrnidae  

Identification: Large size. Dorsal fin proportionately very high and falcate. Leading edge of hammer almost straight with central indent. Body brown to greyish brown. Ventral surface pale.   

Size: Maximum length 6 metres. 50 - 70 cm at birth.  

Habitat: In shore and off shore reefs and surrounding tropical ocean environments. Intertidal to 80 meters.

Abundance and distribution: Circumtropical.

Behavior:  Cruises over sand and reefs in search of prey. Pins stingrays to the sand with hammer whilst disabling them. Swims with an exaggerated swaying of the hammer in order to see forward.

Reproduction: Viviparous. The hammerhead are considered the most highly evolved of the shark families.  

Observations: In the Bahamas I observed yellow jacks rubbing themselves along the flanks of Great Hammerheads possibly ridding themselves of parasites. This shark was observed in the presence of many other reef sharks which are reported to avoid it. The presence of chum in the water may have affected normal social boundaries. 

Photographs: Outer Bahamas.  

Similar species: Scalloped hammerhead distinguished by more pronounced scalloping of hammer and proportionately smaller fins, Smooth Hammerhead distinguished by total lack of indentations in leading edge of hammer, and Smalleye hammerhead distinguished by small size and highly convex anterior margin of hammer. 

Reaction to divers: Shy. Moves away unless in a baited situation. May become very bold and make close passes at divers but not normally aggressive. Care should be taken due to large size and previously reported attacks on bathers. 

Diving logistics: Jim and Anna Abernethy run week long Hammerhead and Tiger shark trips to the Bahamas from Palm Beach. Chum is used to attract the sharks with which they have had great success.  These shark safaris also attract many Caribbean reef sharks and participants should be aware that no cages are used. In my opinion the experience of diving with such large sharks without the restrictions of a cage is second to none. Read the trip report entitled: Hammers and Tigers in the Bahamas.

Other diving locations submitted by readers: 

References and further reading:  

     Reef Sharks and Rays of the World. Scott W. Michael. Sea Challengers.

     Sharks and Rays - Elasmobranch Guide of the World. Ralf M. Hennemann. IKAN.

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