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Scalloped Hammerhead Shark (Sphyrna lewini)

Status | Taxonomy | Species Description | Habitat | Distribution |
Population Trends | Threats | Conservation Efforts | Regulatory Overview |
Key Documents | More Info

  scalloped hammerhead shark
Scalloped Hammerhead Shark
(Sphyrna lewini)
Photo: NOAA

map of scalloped hammerhead dps


ESA Endangered
--Eastern Atlantic "DPS"
--Eastern Pacific "DPS"
ESA Threatened
--Central & Southwest Atlantic "DPS"
--Indo-West Pacific "DPS"
CITES Appendix II - throughout its range

Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Carcharhiniformes
Family: Sphyrnidae
Genus: Sphyrna
Species: lewini

Species Description
Scalloped hammerhead sharks are moderately large sharks with a global distribution. The eight or so species of hammerhead sharks are characterized by the flat, extended head or "cephalofoil." The cephalofoil of a scalloped hammerhead shark is characterized by an indentation located centrally on the front margin of the broadly arched head. Two more indentations flank the main central indentation, giving this hammerhead a "scalloped" appearance.

They feed on crustaceans, teleosts, cephalopods and rays.

The scalloped hammerhead shark is a coastal pelagic species that can also be found in ocean waters and occurs over continental and insular shelves and adjacent to deeper water. It has been observed close inshore and even entering estuarine habitats, as well as offshore to depths of 1000m. Adult aggregations are common at seamounts, especially near the Galapagos, Malpelo, Cocos and Revillagigedo Islands and within the Gulf of California, but otherwise adults can be solitary or occur in pairs.

Scalloped hammerhead sharks are found worldwide residing in coastal warm temperate and tropical seas in the Atlantic, Pacific, and Indian Oceans between 46°N and 36°S to depths of 1000 meters. Distinct Population Segment (DPS) boundaries are shown in the map below:

Population Trends
A recent stock assessment (Hayes et al. 2009) found that the northwestern Atlantic population has decreased from about 155,500 in 1981 to about 26,500 in 2005.


  • targeted fisheries, shark fin trade
  • bycatch

This species is highly desired for the shark fin trade because of its fin size and high fin ray count. They are caught in a variety of fisheries including artisanal and small-scale commercial fisheries, bottom longlines as well as offshore pelagic longlines, gillnets, etc. They are valuable in the international fin and are often used to make shark fin soup. Compilation of market prices from auction records indicates an average, wholesale, unprocessed fin market value of about $50-100 per pound.

Conservation Efforts
In March 2013, at the CITES Conference of the Parties meeting in Bangkok, member nations, referred to as "Parties," voted in support of listing three species of hammerhead sharks (scalloped, smooth, and great) in CITES Appendix II—an action that means increased protection, but still allows legal and sustainable trade. This CITES listing is effective as of September 14, 2014. Export of their fins requires permits that ensure the products were legally acquired and that the Scientific Authority of the State of export has advised that such export is not detrimental to the survival of the species.

Regulatory Overview
On August 14, 2011, we received a petition from WildEarth Guardians and Friends of Animals to list the scalloped hammerhead shark (Sphyrna lewini) as threatened or endangered under the ESA throughout its entire range, or, as an alternative, to delineate the species into DPSs. On November 28, 2011, we published a notice that listing may be warranted, and we commenced a status review. We published the proposed rule to list and status review in April 2013.

Key Documents
(All documents are in PDF format.)

Title Federal Register Date

Final Rule to List 4 DPSs under the ESA

  • ESA Endangered
    • Eastern Atlantic DPS
    • Eastern Pacific DPS
  • ESA Threatened
    • Central and Southwest Atlantic DPS
    • Indo-West Pacific DPS
79 FR 38213 07/03/2014

Status Review Report (updated 2014)


Proposed Endangered and Threatened Listing Determinations for 4 Distinct Population Segments (DPSs)
» Technical corrections to DPS boundary lines

78 FR 20717 04/05/2013

Negative 12-month finding for 2 DPSs

  • Central Pacific DPS
  • NW Atlantic & Gulf of Mexico DPS
78 FR 20717 04/05/2013
CITES Appendix II Proposal   10/04/2012
90-Day Finding on a Petition To List the Scalloped Hammerhead Shark as Threatened or Endangered and Initiation of Status Review 76 FR 72891 11/28/2011
Petition to List Under the ESA n/a 08/2011

More Information

Updated: October 9, 2014

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