Taxon name
Sousa plumbea
(G. Cuvier, 1829)
Uploaded by
National Red List Database
Taxonomic information
Scientific name
Sousa plumbea
(G. Cuvier, 1829)
Assessed taxon level
Species
Higher level taxonomic groupings
Vertebrates
Mammals
Species authority
(G. Cuvier, 1829)
Taxonomic notes and synonyms listed
Sousa plumbea has been recognized as a species since taxonomic revision of the genus Sousa in 2014 (Committee on Taxonomy 2014, Jefferson and Rosenbaum 2014). Previously this species was lumped with the Indo-pacific Humpback Dolphin (Sousa chinensis) but animals occurring in the Indian Ocean from South Africa to India are now recognized as taxonomically distinct from those that occur further east, based on genetics, skeletal morphology, external morphology and colour. There is uncertainty about the taxonomic affinities of the Humpback Dolphins that occur in the Bay of Bengal and future studies will confirm whether S. plumbea actually occurs east of the southern tip of India.
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)
A2bc
Criteria system used
IUCN
(see Assessment details)
Assessment rationale/justification
Preen (2004) reported a 71% decline in small species of dolphins in the Arabian Gulf from 1986 to 1999, which included: Neophocaena phocaenoides, Sousa plumbea and Tursiops aduncus. There is no information available on decline rates in the individual species, so based on the assumption that they all declined equally, it appears reasonable to infer a population reduction of >50% for S. plumbea over the past three generations (75 years). The species, therefore, qualifies for assessment as Endangered (EN) under criterion A2bc. The reduction is thought to be due to a combination of pressures including declining habitat quality because of increasing coastal development, bycatch, collision with boats and declines in fish stocks. The decline is continuing but it is not possible to say if it is at the same rate. The species potentially also qualifies for listing as EN under criterion C1. There is no rescue effect, as the species does not move very far; the species tends to be very localised in its occurrence.
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.
URL (link) of redlist assessment or publication
https://www.moccae.gov.ae/assets/download/b352eff1/UNRL%20of%20Mammals%20-%20Report%202019.pdf.aspx?view=true
Further information
Endemism (according to assessment)
Endemic to region
Not assigned
Taxon distribution as listed in assessment
This species is found throughout the Arabian Gulf waters of UAE at depths up to 30 m. It has not so far been recorded along the UAE east coast (and is absent from the rest of the Sea of Oman as well) although it is known from the Musandam Peninsula. It is seen regularly in the Gulf where small groups are apparently resident in several areas in Abu Dhabi and Dubai coastal waters (Baldwin 2005). It occurs in Marawah Marine Biosphere Reserve, Al Yasat Marine Sanctuary, and around Sadiyat Island (Abu Dhabi) and Jebel Ali Wildlife Sanctuary (Dubai). It was seen frequently off Dubai on a 2015 survey when c. 23 individuals were identified and is sometimes seen very close inshore, such as Dubai Marina. Globally, it is found in a narrow strip of shallow, coastal waters from South Africa, through the coastal waters of East and North Africa, and the Middle East to approximately the southern tip of India and possibly further east (Braulik et al. 2017).
Is there a map available in assessment?
Yes
Habitat and systems
Ecological system type
Habitat
Habitat details as listed in assessment
The species feeds primarily over sand, but also over coral and rocky reefs. Individuals have been known to herd fish onto exposed sandbanks and apparently deliberately beach in order to seize their prey. Observations of mating and adults with calves are recorded for April and May (Baldwin 2005).
Threats and conservation measures listed
Threats listed in assessment
The main threats to cetaceans in UAE waters include: incidental mortality in trawl and drift nets, depletion of prey populations (due in part to commercial overfishing); ship and boat strikes, offshore oil and gas exploration; noise from shipping, submarine sonar and oil and gas rigs. During surveys by EAD, a large number of dolphins were observed with scars that were attributed to propeller cuts, indicating that vessel strike is a major threat to dolphin populations in Abu Dhabi waters (EAD 2015). Inshore and shallow-water species are further threatened by entanglement in abandoned fishing gear; coastal development including port and harbour construction, dredging, land reclamation, residential and tourist development; pollution (oil and hydrocarbons) and damage to feeding grounds and reefs. A UAE Fisheries Resource Assessment Survey in 2002 found that fish stocks in the Gulf had declined by 60%. A lack of information on most species (e.g. population size and trend, the location of critical areas, and feeding ecology) hinders the development of appropriate conservation actions.
History
The backcasted 1996 assessment for this species is Endangered and under the same criterion. The Vulnerable assessment by Hornby (1996) does not appear to have taken into account the 71% decline in the species from 1986 to 1999 as reported by Preen (2004).
Publication
Mallon, D., Hilton-Taylor, C., Allen, D., & Harding, K. (2019). UAE National Red List of Mammals: Marine and Terrestrial. A report to the Ministry of Climate Change and Environment, United Arab Emirates (p. 41). IUCN Global Species Programme. https://bit.ly/2RdZCQR
