Taxon name
Carcharhinus albimarginatus
(Rüppell, 1837)
Uploaded by
National Red List Database
Taxonomic information
Scientific name
Carcharhinus albimarginatus
(Rüppell, 1837)
Assessed taxon level
Species
Higher level taxonomic groupings
Vertebrates
Fishes
Species authority
(Rüppell, 1837)
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)
A2cd
Criteria system used
IUCN
(see Assessment details)
Assessment rationale/justification
In UAE waters, the Silvertip Shark occurs only in the Sea of Oman in continental shelf habitats. 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 longline fisheries that operate within its range outside and surrounding UAE waters. In addition, coral reef loss and degradation have been severe across the UAE. Some management measures are now in place in the Arabian Sea region (i.e. through the IOTC), 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. This species faces intense fishing pressures throughout the Arabian Sea. Based on recorded levels of exploitation and decline in habitat quality, it is suspected to have declined by 60-70% over the past three generation lengths, or about 64 years. It is listed as Endangered A2cd.
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 Silvertip Shark occurs in UAE waters on the Sea of Oman coast. It is excluded from the Arabian Gulf. Globally, it is widespread, but patchy in the Indo-Pacific (Last and Stevens 2009).
Is there a map available in assessment?
Yes
Habitat and systems
Ecological system type
Habitat
Habitat details as listed in assessment
The Silvertip Shark occurs on the continental shelf, offshore islands, coral reefs, and offshore banks, from surface waters to depths of 600-800 m (Compagno et al. 2005). It is also found inside lagoons, near drop-offs, and offshore (Compagno et al. 2005). The species appears to be relatively site-specific for long periods with limited dispersion, particularly at remote and isolated coral reef habitats around tropical islands or atolls (Barnett et al. 2012, Espinoza et al. 2015). On the continental shelf, larger individuals of the species tend to be more mobile and use larger areas than other common reef shark species (Barnett et al. 2012, Espinoza et al. 2015). The Silvertip Shark also exhibits strong diel behaviour, moving closer to coral reefs and using shallower habitats at night.This species reaches a maximum size of 300 cm total length (TL) (Compagno et al. 2005). Males are reported to mature at 160-180 cm TL and females at 160-199 cm TL (Compagno et al. 2005). White et al. (2006) report that males mature at 190-200 cm TL and females at ~195 cm TL. Reproduction is viviparous, with a yolk sac placenta (Compagno et al. 2005, White et al. 2006, White 2007). In a study conducted in Papua New Guinea, males matured at 175 cm TL and 10.5 years, while females matured at 209 cm TL and 14.8 years, and longevity was estimated as 18-32 years for females (Smart et al. 2017). Females give birth to 1-11 pups per litter (average six) biennially, after a 12 month gestation period (Compagno et al. 2005, White et al. 2006, Last and Stevens 2009). Size at birth is reported at 60-68 cm TL (Compagno et al. 2005) and 73-81 cm TL (White et al. 2006). Young are found in shallow water closer to shore, whereas adults are more wide-ranging (Compagno et al. 2005). Growth appears to be fairly slow at about 9 cm per year for juveniles (Last and Stevens 2009). No estimate of generation length is available for the species, although it can be inferred from its congener, the Pigeye Shark (C. amboinensis), which has a similar maximum size and an estimated generation length of 21.5 years (Tillett et al. 2011). When applying an age at first reproduction of 15 years and longevity of 18-32 years, its estimated generation length is 16.5-23.5 years based on the following equation recommended by the IUCN Red List methods: Age at first reproduction + (Age at last reproduction -“ age at first reproduction)/2.
Threats and conservation measures listed
Threats listed in assessment
Information pertaining to threats specific to the UAE are unavailable. This species is impacted by target (for fins and their valuable meat) and bycatch fisheries that are active elsewhere in its range. Marine habitats in the region have experienced high levels of disturbance and are quickly deteriorating due to major impacts from development activities (Sheppard et al. 2010). Corals in the UAE and Arabian Gulf have severely declined due to the increasing frequency of mass bleaching events caused by rising water temperatures, which is a consequence of climate change, as well as pervasive coastal development (Riegl et al. 2018, Burt et al. 2019).
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.
