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Smooth Hammerhead Shark (Sphyrna zygaena)

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


CITES Appendix II - throughout its range

Species Description

up to 880 pounds (400 kg)
8-12 feet (2.5-3.5 m)
Expanded head, in the shape of a hammer, smooth back (lacks a mid-dorsal ridge), tall and curved first dorsal fin with rounded tip, anal fin with a deep notch in the rear margin, fusiform body with dark olive to brown/gray coloring on dorsal side and white underside.
about 20 years
Fishes, cephalopods, crustaceans
Gestation is thought to last 10-11 months, with litter sizes anywhere from 20 to 50 pups
Smooth 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 smooth hammerhead shark is broadly arched with lateral indentations, but does not have the main central indentation like that found on the scalloped or great hammerhead shark


The smooth hammerhead shark is a coastal pelagic species that can also be found in deeper ocean waters, but is usually observed over continental and insular shelves and inshore waters, including bays and estuaries.


Smooth hammerhead sharks are found worldwide in temperate waters and are thought to be the hammerhead species most tolerant of temperate waters. They have also been observed in freshwaters habitats in Florida and Uruguay and in tropical waters.

Population Trends

More information is needed on catches and population trends of smooth hammerhead sharks. Declines in smooth hammerhead populations have been observed in some areas of its range; however, other locations report fairly abundant populations. Because of the similarity in appearances, catches of smooth hammerheads tend to be grouped with those of other hammerhead shark species (mainly great and scalloped), confounding species-specific population trend analyses.


This species is highly desired for the shark fin trade because of its larger fin size and high fin ray count. They are caught in a variety of fisheries including:

They are valuable in the international fin trade and are often used to make shark fin soup. Compilation of market prices from auction records indicates an average, wholesale, unprocessed hammerhead fin market value of US $45-100/lb.

Due to their similarity in appearance to the scalloped hammerhead shark, both the great and smooth hammerhead sharks have been added to CITES Appendix II in an effort to better regulate the international trade of all three species to ensure their sustainability.

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. This action that means increased protection, but still allows legal and sustainable trade. This CITES listing was 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 April 27, 2015, we received a petition from Defenders of Wildlife to list the smooth hammerhead shark (Sphyrna zygaena) as threatened or endangered under the ESA throughout its entire range, or, as an alternative, to delineate the species into distinct population segments (DPSs). On August 11, 2015, we published a notice that listing of smooth hammerhead sharks may be warranted and we commenced a status review of the species. In June 2016, we completed the status review and determined that the species does not warrant listing at this time.


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

Key Documents

(All documents are in PDF format.)
Title Federal Register Date

"Not Warranted" for listing 12-Month Finding

81 FR 41934 06/28/2016
Status Review   06/2016

90-Day Finding on Petition to List Smooth Hammerhead Shark under ESA

80 FR 48053 08/11/2015
CITES Appendix II Proposal   10/04/2012

More Information

Updated: June 28, 2016