Scientific name:
Sphyrna mokarran Identification:
Head hammer shaped, with front edge of the head nearly straight with an indentation in the center; falcate pelvic fins; high dorsal fin (orca-like); free tip of dorsal fin in front of pelvic fin origin; no fin markings. Size:
Birth 50-70 cm (19.7-27.6 inches), maximum length 6m (19.8 ft). Range:
Occurs in most tropical oceans. Depth range from intertidal zone to 80 m (264 ft). Biology:
Feeds on sharks, bony fishes, (catfishes, toadfishes, jacks, herring, groupers, boxfishes), squid, and crustaceans that occur on or near the bottom. Preys heavily on rays (guitarfishes, whiptail stingrays, cownose rays, eagle rays) and skates. Specimens reported with up to 50 stingray and catfish spines broken off in the jaws, throat, and side of the head. Most feeding occurs at dusk. Solitary. Reported to be avoided by other shark species, possibly because it has superior manuverability. Although usually not aggressive, it will make close and unnerving passes toward divers. Its large size makes it worthy of respect; it has been reported to attack bathers.
Scalloped hammerhead shark
Scientific name:
Sphyrna lewini Identification:
Head hammer shaped, with broad head extentions arched posteriorly and an indentation in the middle of the head; pelvic fins not falcate; pectoral fins black tipped or dusky. Size:
Birth 42-55 cm (16.5-21.7 inches), maximum length 4.2 m (13.9 ft). Range:
Found in most warm temperate and tropical seas. Most abundant hammerhead species. Depth range from surface to 275 m (908 ft). Biology:
Adults occur in pelagic and inshore waters, sometimes observed near coral reef drop-offs and often around seamounts. Feeds mainly on bony fishes (mackeral, dolphinfish, squirrelfish, scorpionfish, snake eels, groupers), sharks, rays, squid, crustaceans, and octopuses; rarely on sea snakes. Juveniles feed more on benthic bony fishes and crustaceans, while squid are a more important food source for adults. Although usually indifferent and inoffensive toward divers, it may become aggressive in baited situations. It will occasionally make close approaches to the diver, even when feeding stimuli are not present.
Smooth hammerhead shark
Scientific name:
Sphyrna zygaena Identification:
Head hammer shaped with no indentation in front edge, but is rounded; free tip of the first dorsal fin does not extend back to pelvic fin origin. Size:
Birth 50-61 cm (19.7-24 inches), maximum length 4 m (13.2 ft). Range:
Worldwide, in warm temperate and tropical seas. Depth range from surface to 20 m (66 ft). Biology:
Usually over deeper water in oceanic habitats. However, it also occurs in shallow coastal waters, including areas around rocky reefs. Its primary prey are squid and bony fishes (herring, mackerel, groupers, jacks, mullet, barracuda, needlefishes, filefishes), but in certain areas it also feeds heavily on small sharks, rays (whiptail stingrays, spotted eagle rays), and skates. Solitary or in huge migratory schools. It engages in migrations to warmer waters in the winter. Usually indifferent toward divers, it may make close passes, but can be aggressive in baited situations.