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Hammerhead sharks are iconic with their hammer-shaped head! What distinguishes the scalloped hammerhead from their other species in the genus is their scalloped shaped cephalofoil (i.e. their hammerhead), which has a prominent grove in the centre and two either side! The body is slender and generally individuals have a uniform colouration ranging from olive-bronze-brown-grey on the dorsal side and white on the ventral. Not only this, but the tips of their pectoral fins on the ventral side are either black or grey in colouration which can disappear with age. The scalloped hammerhead is also known to have a high dorsal fin and the second dorsal has a long free rear tip which almost reaches the upper caudal lobe (the top lobe of the caudal fin). This beautiful species can reach up to ca. 4.3m!
This species is distributed in warm and tropical waters across the globe, including the Mediterranean Sea! Baum et al. (2007) states that the lower limit of the species is at least 275m and is both coastal and semi-pelagic.
The primary prey item for the scalloped hammerhead is teleost (bony fish; Shark Trust, 2010) but it has been known to feed on other organisms such as cephalopods, crustaceans and stingrays.
The species is listed as “endangered” under the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Not only this, but in 2014 the species was also listed under Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS), meaning they are conserved through international agreements, as well as Annex 1 (Highly Migratory Species) of The United Nations Convention of the Law of the Sea (UNCLOS).
A wide range of fishing practices remove scalloped hammerheads froms our oceans as both a target and bycatch species. Such practices include trawling, purse-seine, longline, and gillnet fishing (Baum et al., 2013). Due to their aggregating behaviour and presence in shallow waters, this species is also vulnerable to inshore and artisanal fisheries (Shark Trust, 2010; Baum et al., 2013).
The high fin ray count and size of its fins (NOAA Fisheries, 2015) also make the scalloped hammerhead a highly desired species for shark fin soup.
Baum J, Clarke S, Domingo A, Durcocq M, Lamónaca AF, gaibor N, Graham R, Jorgensen S, Kotas JE, Medina E, Martinez-Ortiz J, Monzini Taccone di Sitizano J, Morales MR, Navarro SS< Pérez-Jiménez JC, Ruiz C, Smith W, Valenti SV and Vooren CM. 2007. Sphyrna lewini. The IUCN Red List of Threatened Species 2007: e.T39385A10190088. http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T39385A10190088.en. Last accessed 18th February 2017.
Shark Trust. 2010. An illustration compendium of sharks, skates, rays and chimaera. Chapter 1: The British Isles and Northeast Atlantic. Part 2: Sharks. Available at: http://www.sharktrust.org/shared/downloads/factsheets/scalloped_hammerhead_shark_st_factsheet.pdf . Last accessed 18th February 2017.
NOAA Fisheries. 2015. Scalloped Hammerhead Shark (Sphyrna lewini). Available at: http://www.fisheries.noaa.gov/pr/species/fish/scalloped-hammerhead-shark.html. Last accessed 18th February 2017.
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