Taxon name
Alopias pelagicus
Nakamura, 1935
Uploaded by
National Red List Database
Taxonomic information
Scientific name
Alopias pelagicus
Nakamura, 1935
Assessed taxon level
Species
Higher level taxonomic groupings
Vertebrates
Fishes
Species authority
Nakamura, 1935
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 Pelagic 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 Pelagic Thresher shark occurs in UAE waters on the Sea of Oman coast. It is likely excluded from the Arabian Gulf (Compagno 2001). 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.
Is there a map available in assessment?
Yes
Habitat and systems
Ecological system type
Habitat
Habitat details as listed in assessment
The Pelagic Thresher is epipelagic and mesopelagic from the surface to 300 m depth (Weigmann 2016). It attains a maximum size of 365 cm total length (TL). In the Arabian Sea, males are reported to mature at 245-270 cm TL while females mature between 268-286 cm TL (Varghese et al. 2017). The species is lecithotrophic viviparous with oophagy, and a litter size of only two very large (158-190 cm TL) pups. Age at maturity near Taiwan is estimated as 8-9.2 years in females and 7-8 years in males (Liu et al. 1999). Its potential annual rate of population increase under sustainable fishing is thought to be very low and has been estimated at 2-4% (Smith et al. 1998), or 0.033 (Dulvy et al. 2008), compared with the Common Thresher, which is between 4 and 7% (Smith et al. 1998) or 0.254 (Dulvy et al. 2008). Generation length is estimated at 18.6 years (Drew et al. 2015).
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). This species has the lowest intrinsic rebound potential and least resistance to fisheries of the genus (Chen et al. 1997). It has a particularly low (2-4%) annual rate of population increase.
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.
