Taxon name
Rhynchobatus australiae
Whitley, 1939
Uploaded by
National Red List Database
Taxonomic information
Scientific name
Rhynchobatus australiae
Whitley, 1939
Assessed taxon level
Species
Higher level taxonomic groupings
Vertebrates
Fishes
Species authority
Whitley, 1939
Taxonomic notes and synonyms listed
Rhynchobatus australiae is part of the Indo-West Pacific Rhynchobatus djiddensis species-complex. The name R. djiddensis has previously been used widely, leading to poorly-defined taxonomy and distributions for members of the complex (in particular, R. australiae, R. djiddensis, and R. laevis). Further investigation into the taxonomy of 'whitespotted wedgefish' is required, and additional species are likely to be described in the future.
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)
A2bcd
Criteria system used
IUCN
(see Assessment details)
Assessment rationale/justification
The Bottlenose Wedgefish occurs throughout UAE inshore and offshore waters. There has been a total ban on fishing for this species in UAE waters since 2019. The similarity of the three species of Rhynchobatus that occur in the region mean there are few reliable species-specific data available. It is commonly taken as bycatch in gill net, longline and trawl fisheries and its fins are highly valued in international trade. Coastal development is causing habitat degradation, which may also be impacting this species. Significant declines are known in India, southern Oman, Pakistan and Iran. It exhibits 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 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, landings data and decline in habitat quality, it is suspected to have declined by 50-80% over the past three generation lengths, or about 39 years. It is listed as Endangered A2bcd.
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 Bottlenose Wedgefish occurs throughout UAE waters. Globally, it is widespread in the Indo-West Pacific (Last et al. 2016, Giles et al. 2016). However, the difficulties in distinguishing between species of Rhynchobatus causes some of its distribution to be uncertain.
Is there a map available in assessment?
Yes
Habitat and systems
Ecological system type
Habitat
Habitat details as listed in assessment
This species occurs in inshore and offshore waters over soft substrates to depths of 60 m or more (Last et al. 2016), but can also be associated with coral reefs. It attains a maximum size of about 300 cm total length (TL) with males mature at about 124 cm TL (Last et al. 2016). Size at birth is unknown, although the closely related R. djiddensis is born at about 60 cm TL. Maximum age for Rhynchobatus spp. in Australia is 5 years (males) and 12 years (females), but these data were not from the largest individuals (White et al. 2014) and are not reliable for the estimation of generation length. This is therefore estimated from the maximum age (19 years) and age at maturity (7 years) taken from the growth curve provided by White et al. (2014) for the Giant Guitarfish (Glaucostegus typus), which gives an estimated generation length of 13 years.
Threats and conservation measures listed
Threats listed in assessment
This species is impacted by target and bycatch fisheries in the UAE. It may also being impacted by habitat degradation due to coastal development, especially nursery grounds. Marine habitats in the Gulf are experiencing high levels of disturbance and quickly deteriorating due to major impacts from development activities (including dredging and reclamation), desalination plants, industrial activities, habitat destruction through the removal of shallow productive areas and major shipping lanes (Sheppard et al.<em style=""font-size: 12pt; font-family: Georgia;""> 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.
