Taxon name
Alopias superciliosus
Lowe, 1841
Uploaded by
National Red List Database
Taxonomic information
Scientific name
Alopias superciliosus
Lowe, 1841
Assessed taxon level
Species
Higher level taxonomic groupings
Vertebrates
Fishes
Species authority
Lowe, 1841
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)
A2bd
Criteria system used
IUCN
(see Assessment details)
Assessment rationale/justification
In UAE waters, the Bigeye Thresher Shark occurs only in the Sea of Oman. Little specific data are available for this species in the UAE. It is apparently highly migratory, and has slow life history characteristics including low fecundity and a low annual rate of population increase. Considering this, the species has a low capacity to recover from even moderate levels of exploitation. It is especially susceptible to exploitation (target and bycatch) in many largely unregulated and under-reported gillnet and longline fisheries that operate within its range outside and surrounding UAE waters. Some management measures are now in place in the Arabian Sea region (i.e. through the IOTC), although domestic fisheries are likely to continue. A total ban of fishing for this species has been in place in UAE waters since 2019. 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. This species faces intense fishing pressures throughout the Arabian Sea. Based on fisheries data and recorded levels of exploitation, it is suspected to have declined by at least 50% over the past three generation lengths, or about 57 years. It is listed as Endangered A2bd.
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 Bigeye Thresher Shark occurs in UAE waters on the Sea of Oman coast to the Strait of Hormuz. It is likely excluded from the Arabian Gulf (Compagno 2001, Owfi et al. 2016). An Alopias species was reported by a diver at an offshore wreck in Dubai. An archaeological study found four caudal vertebrae belonging to thresher shark species in Abu Dhabi (Beech 2004). Globally, it is wide-ranging in the Indo-Pacific and Atlantic Oceans.
Is there a map available in assessment?
Yes
Habitat and systems
Ecological system type
Habitat
Habitat details as listed in assessment
The Bigeye Thresher Shark is found in coastal waters over continental shelves, sometimes in shallow inshore waters, and on the high seas in the epipelagic and mesopelagic zones far offshore; it is also caught near the bottom in deep water on continental slopes (Compagno 2001). It occurs mostly shallower than 100 m, but has been recorded to 995 m (Compagno 2001, Coelho et al. 2015). It attains a maximum recorded size of 484 cm total length (TL) (Compagno 2001). Males are reported to mature at 245-300 cm TL while females mature between 282-355 cm TL (Chen et al. 1997, Liu et al. 1998, Moreno and Moron 1992, Stillwelli and Casey 1976, Varghese et al. 2017). Size at birth ranges from 64-140 cm TL (Golani 1996, Chen et al. 1997, Bauchot 1987). The gestation period is 12 months with average litter sizes 2-4 pups/litter, usually two (Compagno 2001, Varghese et al. 2017). Of the thresher sharks, the Bigeye Thresher has the lowest rate of annual increase, estimated at 1.6% under sustainable exploitation (Smith et al. 2008), or 0.002-0.009 (Cortés 2008, Dulvy et al. 2008). Estimated age at maturity is years 12-13 for females, and 9-10 years for males (Liu et al. 1998) (data from Taiwan waters, Northwest Pacific). Longevity is estimated at 20 years for females (19 years for males) (Liu et al.1998). Generation is estimated at 18.5 years based on studies from the east China Sea (Chen and Yuan 2006).
Threats and conservation measures listed
Threats listed in assessment
Information pertaining to threats specific to the UAE are unavailable. Thresher sharks are impacted by target (for fins and their valuable meat) and bycatch fisheries throughout their range. Finning and discarding of carcasses has also been reported, especially in offshore and high seas fisheries (Anderson and Simpfendorfer 2005, IOTC 2006). Hooking mortality is apparently very high, between 60-70% of fish caught are dead on haulback (Coehlo et al. 2011, IOTC 2016). The Bigeye Thresher Shark has the lowest intrinsic rebound potential and least resistance to fisheries of the genus (Chen et al. 1997).
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.
