@article{,

title = {Tursiops aduncus},

author = {Braulik, G.,Natoli, A.,Kiszka, J,Parra, G.,Plon, S.,Smith, B.D.},

url = {https://www.iucnredlist.org/species/41714/50381127},

doi = {https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T41714A50381127.en},

year  = {2019},

date = {2019-01-01},

journal = {IUCN Red List of Threatened Species},

volume = {Downloaded on 20 April 2020},

number = {50},

abstract = {Near-threatened:  Justification: Indo-Pacific Bottlenose Dolphins generally occur in shallow coastal waters of the Indian Ocean,

Southeast Asia and Australia. They are among the more commonly studied cetaceans in the Indian

Ocean, especially in Shark Bay, Western Australia. However, information on distribution, population size,

and trends in abundance and mortality from much of the species’ range is still very limited. As they are

primarily coastal, Indo-Pacific Bottlenose Dolphins often co-occur with fisheries, and bycatch is a major

cause of concern for this species. Indo-Pacific Bottlenose Dolphins are also at risk from high levels of

noise and chemical pollution, industrial activity such as oil and gas development, and habitat reduction

caused by land reclamation and coastal development (Curry and Smith 1997, Wells and Scott 1999,

Reeves et al. 2003, Kiszka et al. 2008). Furthermore, survey data suggest that Indo-Pacific Bottlenose

Dolphins occur in relatively small populations or communities with limited geographic ranges, especially

where they reside close to islands (Krützen et al. 2004, Natoli et al. 2008, Fury et al. 2008, Särnblad et al.

2011, Kiszka et al. 2012, Gray et al. 2018), which can exacerbate the impact of human activities and

demographic stochasticity on this species. Estimates of abundance from populations for which

information on bycatch is also available indicate that human-caused mortality is frequently

unsustainable (Cockcroft et al. 1992, Shirakihara and Shirakihara 2012, Preen 2004). Based on the sum

of existing abundance estimates, the total population size for the species over its entire range is likely

well in excess of 40,000 individuals. Large parts of the range have never been surveyed (e.g. much of the

Arabian Sea, Arabian/Persian Gulf, Pakistan, India, Red Sea, Somalia, Yemen, Mozambique, Indonesia,

Philippines). The Indo-Pacific Bottlenose Dolphin was classified as Data Deficient in 2008. The species

distribution overlaps the range of several other coastal cetacean species that are red-listed as

Endangered (Irrawaddy Dolphin Orcaella brevirostris and Indian Ocean Humpback Dolphin Sousa

plumbea) or Vulnerable (Indo-Pacific Humpback Dolphin Sousa chinensis and Australian Humpback

Dolphin Sousa sahulensis, Australian Snubfin Dolphin Orcaella heinsohni and the Indo-Pacific Finless

Porpoise Neophocaena phocaenoides) and are subject to the same anthropogenic threats. However,

compared to these other species, the Indo-Pacific Bottlenose Dolphin is assumed to be under less

immediate threat because it has a wider geographic range and probably larger numbers, greater

behavioural plasticity and broader habitat preferences. Data are insufficient to present a robust case for

listing the Indo-Pacific Bottlenose Dolphin in a threatened category (CR, EN, or VU). However, its coastal

distribution, inferred local declines, and intensity of threats throughout its range lead to the conclusion

that Least Concern is not an appropriate category. The Red List Guidelines (version 11, 2014) state that

“the category Near Threatened is applied to taxa that do not qualify as threatened now, but may be

close to qualifying as threatened, and to taxa that do not currently meet the criteria for a threatened

category, but are likely to do so if ongoing conservation actions abate or cease.” Also, to qualify for Near

Threatened, the taxon “should be close to qualifying for the Vulnerable category; estimates of

population size or habitat should be close to the Vulnerable thresholds, especially when there is a high

degree of uncertainty, or possibly meet some of the subcriteria; and this may be combined with

biological susceptibility and threat.” Considering the above, the Indo-Pacific Bottlenose Dolphin is listed

as Near Threatened because: 1) it occurs in a relatively small and restricted near-shore range, 2) it is

highly vulnerable to entanglement in fishing gear and its range overlaps with intensive fisheries known

to entangle and kill dolphins, 3) its near-shore habitat is subject to increasing anthropogenic threats

resulting in habitat loss and degradation, and 4) it is experiencing mortality rates that are likely to be

causing population declines in several areas. The species therefore comes close to meeting criterion A4

for Vulnerable. Population size is inferred and suspected to have declined by close to 30% throughout

the range of the species, over three generations and in a time period encompassing the past, present

and future. The causes of the reduction (gillnet entanglement and coastal habitat degradation) have not

ceased. Generation length for Indo-Pacific Bottlenose Dolphins, according to Taylor et al. (2007), is 21.1

years, therefore three generations is 63.3 years. Thus, an annual decline of around 0.5% would result in

exceeding the 30% decline in 3 generations. Gillnet fisheries and coastal development are increasing

throughout the range of the species and bycatch is anticipated to remain stable or to increase in the

future without urgent and intensive efforts which are unlikely to be forthcoming. It is important to

emphasize that numerous isolated populations of this species would likely qualify as threatened

subpopulations, particularly those found around island groups in the Indian Ocean.},

keywords = {conservation status, indo-Pacific bottlenose dolphin, IUCN, Red List, tursiops aduncus},

pubstate = {published},

tppubtype = {article}

}