The family Sphyrnidae, commonly known as hammerhead sharks, is easily recognized by its distinctive, flattened, T-shaped head structure called the cephalofoil. This unique morphology helps the shark in sensing its environment and maneuvering through the water. While there are nine species of hammerheads, the largest member of this group is the Great Hammerhead, scientifically named Sphyrna mokarran.
The Great Hammerhead Defining Its Size
The maximum reported length for this shark is approximately 6.1 to 6.2 meters (about 20 feet), though specimens of this size are rare. The typical length for a mature adult Great Hammerhead is closer to 3.5 to 4.6 meters (11 to 15 feet).
In terms of mass, the largest individuals are documented weighing up to 580 kilograms (1,280 pounds). This record-holding shark was a female caught off the coast of Florida, and her significant weight was partly attributed to her being pregnant. Most large adults generally weigh between 200 and 500 kilograms, making them heavier than the next largest species, the Scalloped Hammerhead (Sphyrna lewini).
Unique Physical Characteristics
The defining cephalofoil has a broad, almost straight front margin, lacking the pronounced central indentation found in species like the Scalloped Hammerhead. This wide, smooth leading edge is a reliable characteristic for field identification of the adult Great Hammerhead. The first dorsal fin is a prominent feature, being exceptionally tall, strongly recurved, and sickle-shaped, or falcate. This fin originates directly over the insertion point of the pectoral fins, giving the shark a robust and powerful silhouette. The pelvic fins are also distinctly falcate, contrasting with the straight-edged pelvic fins of the Scalloped Hammerhead.
Global Habitat and Vulnerability
The Great Hammerhead is a cosmopolitan species, found across tropical and warm temperate waters globally, ranging between approximately 40° North and 37° South latitudes. It occupies diverse marine environments, from shallow coastal areas and coral reefs to depths of up to 300 meters along the continental shelf and island terraces. This shark is highly migratory, with populations often moving poleward toward cooler waters during the summer months. The species is heavily impacted by human activity, leading the International Union for Conservation of Nature (IUCN) to classify it as Critically Endangered worldwide.
The primary factor driving population declines is overexploitation in both targeted fisheries and as incidental bycatch. The large, valuable fins of the Great Hammerhead are highly sought after in the global fin trade, which contributes substantially to its high mortality rate. The species is also biologically susceptible to depletion because females only reproduce once every two years, resulting in a slow population recovery rate.