Sphyrna lewini
Scalloped Hammerhead Shark [+]

Kingdom: Animalia
Phylum: Chordata
Class: Elasmobranchii
Order: Carcharhiniformes
Family: Sphyrnidae
Genus: Sphyrna
species: Sphyrna lewini
+ITIS +WoRMS +Conservation Status

Description & Behavior

Video: Scalloped Hammerhead sharks of the Galapagos (1:40 | 5.8MB)

The scalloped hammerhead, Sphyrna lewini (Griffith and Smith, 1834), is a large hammerhead shark with a moderately high first dorsal fin and low second dorsal and pelvic fins. It can be distinguished by the broadly arched front margin of head that has a prominent median notch (see the great hammerhead for a comparison between the great, scalloped hammerhead and bonnethead sharks). Side wings of head narrow, rear margins swept backward. The scalloped hammerhead is uniformly gray, gray-brown, or olive on the dorsal surface, fading to white on the ventral surface and its pectoral fins are tipped with gray or black ventrally. Most sharks encountered by divers average 2-2.5 m in length. Males mature at 1.5-1.75 m and reach an average of 3 m, females mature at about 2 m. Maximum length of this species is known to be at least 3.7 m, and it is thought that a few individuals may reach a length of over 4 m.

World Range & Habitat

Scalloped hammerheads, Sphyrna lewini, are coastal-pelagic, semi-oceanic sharks occurring over continental and insular shelves and adjacent deep water, often approaching close inshore and entering enclosed bays and estuaries. Found in inshore and offshore waters to about 275 m depth. Huge schools of small migrating individuals move poleward in the summer in certain areas. Permanent resident populations also exist. Adults solitary, in pairs, or schools; young in large schools.

» GBIF occurrence data in Google Earth [Requirements | Tips] | Ocean Biogeographic Information System (OBIS) [World Map] | [about]

Feeding Behavior (Ecology)

Scalloped hammerheads, Sphyrna lewini, feed mainly on teleost (bony) fishes and cephalopods (squid, octopus, and cuttlefishes), also lobsters, shrimps, crabs, as well as other sharks and rays. In the Indo-West Pacific stomach contents have been found to include sea snakes.

Life History

Scalloped hammerheads are viviparous, with a yolk-sac placenta. Pups are born following a 12 month gestation. Produces 15-31 pups, of 43-55 cm young in a litter. Pups occupy shallow coastal nursery grounds, often heavily exploited by inshore fisheries, and then migrate offshore as they mature.

Comments

Scalloped hammerhead sharks are considered potentially dangerous to people but usually nonaggressive and shy when approached by divers. Under baited conditions scalloped hammerheads may make close approaches to divers but quickly lose interest and depart when they determine that the divers are not the source of the food odors.

Readily available to inshore small commercial fisheries as well as to offshore operations. Sold fresh, dried-salted, smoked and frozen; also sought for its fins and hides. Oil used for vitamins and carcasses for fishmeal. Lack of data on population trends makes it difficult to assess whether the high level of catches of this species at all life stages is having an effect on stocks, but some declines are reported.

The scalloped hammerhead shark is listed as Lower Risk/near threatened (LR/nt) on the IUCN Red List of Threatened Species:

LOWER RISK (LR) - A taxon is Lower Risk when it has been evaluated and does not satisfy the criteria for any of the categories Critically Endangered, Endangered or Vulnerable. Taxa included in the Lower Risk category can be separated into three subcategories:

1. Conservation Dependent (cd). Taxa which are the focus of a continuing taxon-specific or habitat-specific conservation programme targeted towards the taxon in question, the cessation of which would result in the taxon qualifying for one of the threatened categories above within a period of five years.
2. Near Threatened (nt). Taxa which do not qualify for Conservation Dependent, but which are close to qualifying for Vulnerable.
3. Least Concern (lc). Taxa which do not qualify for Conservation Dependent or Near Threatened.

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References & Further Research

BioOne ~ CITES ~ Discover Life ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList ~ MarineBio Network ~ NCBI ~ SCIRIS ~ SIRIS ~ Tree of Life Web Project ~ Wikipedia

Scalloped Hammerhead Sharks at HIMB
David Hall's Encounters in the Sea

Search the Web for Scalloped Hammerhead Shark » ARKive ~ Ask.com ~ Ask Jeeves ~ bing ~ deviantART ~ dmoz ~ Dogpile ~ Google Images ~ MySpace Images ~ OceanFootage ~ Picsearch ~ StumbleUpon ~ Yahoo! Images ~ YouTube

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Citation: Sphyrna lewini, Scalloped Hammerhead Shark - MarineBio.org. Retrieved , from .

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Sphyrna lewini Scalloped Hammerhead Shark [+]