The scalloped hammerhead can grow to over 13 feet in length. Their maximum weight is about 340 pounds. They have bronze or light gray backs, a white underside, dark-tipped fins and a dark blotch on the lower lobe of their caudal fin (tail).
The head of a scalloped hammerhead shark has narrow blades with a notch in the center and indentations on the front edge. Their eyes are located at the end of each blade. They have a large first dorsal fin and a smaller second dorsal fin. They have 5 gill slits.
Young scalloped hammerheads may be found in schools, while adults may be found in schools, pairs or singly.
- Kingdom: Animalia
- Phylum: Chordata
- Subphylum: Gnathostomata
- Superclass: Pisces
- Class: Elasmobranchii
- Subclass: Neoselachii
- Infraclass: Selachii
- Superorder: Galeomorphi
- Order: Carcharhiniformes
- Family: Sphyrnidae
- Genus: Sphyrna
- Species: lewini
Habitat and Distribution:
Scalloped hammerhead sharks may be found in warm temperate and tropical waters, from bays, estuaries inshore areas out to deep water up to about 900 feet.
In the U.S., they are found in the western Atlantic Ocean from New Jersey to Uruguay, including in the Gulf of Mexico, and in the Pacific Ocean from southern California to South America, and off Hawaii. They are also found in the eastern Atlantic Ocean from the western Mediterranean Sea to Namibia, and in the Red Sea, Indian Ocean, and western Pacific Ocean from Japan down to Australia.
Scalloped hammerheads may gather in large schools for breeding. Females give birth in shallow waters in summer. This shark species is viviparous - scalloped hammerheads give birth to live young after a 9-10 month gestation period. While the young are developing, they are nourished by a yolk sac placenta.
The pups are about 1.5 feet long when born, and 13-31 pups are in each litter. According to FishBase, the maximum reported age of a scalloped hammerhead is 35 years.
Scalloped hammerheads are generally not considered dangerous to humans. Hammerhead sharks in general (because attacking sharks aren't always identified to species) are listed by the International Shark Attack File #8 on its list of species responsible for shark attacks from the years 1580 to 2011. During this time, hammerheads carried out 17 non-fatal, unprovoked attacks and 20 fatal, provoked attacks.
Scalloped hammerhead sharks are listed as endangered by the IUCN Red List, due to their high rate of bycatch in fishing gear, and harvest in shark finning operations. They are also more vulnerable to capture than some other fish because of their schooling behavior.
These sharks may also be captured for their meat, skin and oil (which is used for vitamins) and to be used as fishmeal.
References and Further Information:
- ARKive. Scalloped Hammerhead. Accessed June 30, 2012.
- Baum, J., Clarke, S., Domingo, A., Ducrocq, M., Lamónaca, A.F., Gaibor, N., Graham, R., Jorgensen, S., Kotas, J.E., Medina, E., Martinez-Ortiz, J., Monzini Taccone di Sitizano, J., Morales, M.R., Navarro, S.S., Pérez-Jiménez, J.C., Ruiz, C., Smith, W., Valenti, S.V. & Vooren, C.M. 2007. Sphyrna lewini. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1.
. Accessed June 30, 2012.
- Bester, Cathleen.Scalloped Hammerhead. Florida Museum of Natural History. Accessed June 30, 2012.
- Carpenter, K.E. Great Hammerhead: Sphyrna lewini. Accessed June 30, 2012.
- Compagno, L., Dando, M. and S. Fowler. 2005. Sharks of the World. Princeton University Press.
- Florida Museum of Natural History. 2012. ISAF Statistics on Attacking Species of Shark. Accessed June 30, 2012.
- Krupa, D. 2002. Why the Hammerhead Shark's Head is In the Shape It's In. American Physiological Society. Accessed June 30, 2012.