The scalloped hammerhead shark is one of ten species of hammerhead sharks and it is distinguished by its uniquely shaped cephalofoil. The cephalofoil has a pronounced notch in the center with several smaller notches making it resemble the shell of a scallop. They have a large slightly hooked first dorsal fin and a smaller second fin. Their coloring is typically uniform grey to greyish brown with a white underside.
At-A-Glance
Scientific Name – Sphyrna lewini
Size – Can range from 6-12ft/1.8-3.6m depending on sex and age.
Habitat – Found worldwide in pelagic waters off and on continental shelves of the Atlantic, Indian, and Pacific Oceans. They can also be found in coastal waters, but they are a highly migratory species.
Diet – Variety of fish species like mackerel or sardines, cephalopods, stingrays and even other types of sharks.
Reproduction – Females reach sexual maturity around 15 years and males at 10 years. Viviparous; mate via internal fertilization and give birth to live young with a gestation period lasting around 8-12 months; a litter can range from 12–40 pups.
Lifespan – 30 years.
IUCN Listing – Critically Endangered.
Protection – Listed under Appendix II of CITES, listed under Appendix III of SPAW, populations in the Central and Southwest Atlantic and the Indo-West Pacific are listed under the U.S. Endangered Species Act as threatened, populations in the Eastern Atlantic and Eastern Pacific are listed under the U.S. Endangered Species Act as endangered.
Bet You Didn’t Know…
- Scalloped Hammerheads are a highly migratory species and can be found in large schools, sometimes with hundreds of individuals. These large schools can be a disadvantage as their fins are highly sought after in the fin trade and large numbers are often caught during their seasonal migrations.
- Scalloped hammerheads have a large complex brain which promotes high levels of cognitive ability, social intelligence, intricate migrations, and athletic capture of prey. Their social intelligence is especially important for their aggregate behavior, which favors the mating of the fittest members of the group to ensure the proliferation of the species.
- Scalloped hammerheads are fond of eating stingrays and seemed unperturbed by their venomous barbs. One shark was found with 96 stingray barbs stuck around its mouth and head!
Ready To Dive In?
- Darwin & Wolf Island, Galápagos: January to May.
- Cocos Island, Costa Rica: May to September.
- Revillagigedo Archipelago, Mexico: April to June.
- Gordo Banks, Mexico.
- Rangiroa, French Polynesia: January to February.
- Alphonse Island, Seychelles: March to May and October to December.
- Lahaina, Hawaii: May to September.
Science In The Spotlight
A new nursery for juvenile scalloped hammerheads has been discovered at an island in the Galápagos Marine Reserve. In 2017, a chance discovery of scalloped hammerhead shark pups incited a chain of surveys starting in 2018. These surveys used techniques such as underwater video footage and tagging to investigate the presence of these pups in Puerto Grande, a shallow bay by the island of San Cristobal. Tags tracking four individual pups demonstrated that the pups stayed in Puerto Grande at least 89% of the time. This finding, in addition to other observations and data, established Puerto Grande as a crucial nursery for scalloped hammerheads.
Written by Golda Stewart for her Capstone Project.
Photos: Michele Westmorland, Jamie Pollack.