Taxon name
Sphyrna zygaena
(Linnaeus, 1758)
Uploaded by
National Red List Database
Taxonomic information
Scientific name
Sphyrna zygaena
(Linnaeus, 1758)
Assessed taxon level
Species
Higher level taxonomic groupings
Vertebrates
Fishes
Species authority
(Linnaeus, 1758)
Location and scope
Specific locality or subnational name or regional name
United Arab Emirates (the)
Scope (of the Assessment)
National
Countries included within the scope of the assessment
United Arab Emirates (the)
Does the assessment cover a marine EEZ area(s)?
Not_assigned
Conservation Status
Qualifying criteria (if given)
A2d
Criteria system used
IUCN
(see Assessment details)
Assessment rationale/justification
In UAE waters, the Smooth Hammerhead occurs only in the Sea of Oman. Capture of this species is totally banned in the UAE. It is sometimes confused with the more abundant Scalloped Hammerhead (Sphyrna lewini). This species is caught in both coastal and oceanic fisheries, and its low productivity causes it to be susceptible to rapid population declines from exploitation. Its fins are highly valued, and this is driving increased targeted fishing in some areas. Despite the lack of data, the similar ecology, low productivity, and presence of intensive fisheries, mean that this species, like other large sharks in the Arabian Sea region, has likely undergone significant declines. It is especially susceptible to exploitation (target and bycatch) in many largely unregulated gill net, longline and trawl fisheries that operate within its range outside and surrounding UAE waters. Some management measures are now in place in the Arabian Sea region, although domestic fisheries are likely to continue. Though data specifically from the UAE are not available, individuals in the UAE are a component of a larger, interconnected and migratory population that occurs broadly in the north-western Indian Ocean. It is inferred that declines reported in the Arabian Sea region are representative of its status in the UAE. Based on recorded levels of exploitation, it is suspected to have declined by at least 50% over the past three generation lengths, or about 72 years. It is listed as Endangered A2d.
Assessment details
Assessors/contributors/reviewers listed
UAE National Red List Workshop
Criteria system used
IUCN
Reference for methods given
IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1, Second edition. IUCN, Gland, Switzerland and Cambridge, UK. iv + 32pp pp. And IUCN. 2012. Guidelines for Application of IUCN Red List Criteria at Regional and National Levels: Version 4.0. Gland, Switzerland and Cambridge, UK: IUCN. iii + 41pp.
Further information
Endemism (according to assessment)
Endemic to region
Not assigned
Taxon distribution as listed in assessment
The Smooth Hammerhead occurs in UAE waters on the Sea of Oman coast. It is apparently excluded from the Arabian Gulf (Last and Stevens 1994). Records from the Gulf may be misidentifications of Sphyrna mokarran (Ali et al. 2018). Globally, it occurs in all coastal and open ocean temperate and tropical waters (Ebert et al. 2013). The full extent of this species' range in tropical waters may be incompletely known at present due to confusion with the more abundant Scalloped Hammerhead (Sphyrna lewini).
Is there a map available in assessment?
Yes
Habitat and systems
Ecological system type
Habitat
Habitat details as listed in assessment
The Smooth Hammerhead is a coastal-pelagic and semi-oceanic species that occurs on the continental shelf, to at least 200 m depth, with large individuals often found over deep reefs on the edge of the shelf (Smale 1991, Ebert et al. 2013). Despite its widespread occurrence, there are only limited published biological data on this species. It attains a maximum size of 370-400 cm total length (TL) (Ebert et al. 2013, Weigmann 2016). Stevens (1984) reported that off the east coast of Australia males mature at about 250-260 cm TL and females at about 265 cm TL with parturition and ovulation occurring between January and March. The gestation period off eastern Australia would appear to be 10-11 months. Castro and Mejuto (1995) reported 21 gravid females with a mean litter size of 33.5 from the waters of western Africa. Off eastern Australia, Stevens (1975) reported litter sizes between 20-49 (mean 32). The sex ratio of embryos is 1:1 (Stevens 1984, Castro and Mejuto 1995). Compagno (1984) and Compagno et al. (2005) gave the size at birth as 50-61 cm. Smale (1991) and Doño (2008) reported juveniles with open umbilical scars from South Africa at sizes between 59 and 63 cm, and from Uruguay between 49 and 55 cm TL, respectively. Although maximum age has yet to be determined for this species, it is thought that the lifespan of the Smooth Hammerhead may be 20 years or longer (FLMNH 2008). Generation length is estimated at 24 years based on that for the Scalloped Hammerhead (S. lewini), which reaches a similar size (Drew et al. 2015).
Threats and conservation measures listed
Threats listed in assessment
This species is impacted by target and bycatch fisheries across its range. Finning and discarding of carcasses has also been reported, especially in offshore and high seas fisheries (Anderson and Simpfendorfer 2005). This species is being increasingly targeted in some areas in response to increasing demand for the fins (Jabado et al. 2015).
Publication
Ralph, G.M., Stump, E., Linardich, C., Bullock, R.W., Carpenter, K.E., Allen D.J., Hilton-Taylor, C., Al Mheiri, R., and Alshamsi, O. 2021. UAE National Red List of Marine Species: Reef-building corals, cartilaginous fishes and select bony fishes. 2021. Ministry of Climate Change and Environment, Dubai, United Arab Emirates.
