Overview

Distribution

Range Description

Australian snubfin dolphins inhabit coastal, shallow waters of the tropical and subtropical zones of Australia, and possibly some parts of New Guinea (Beasley et al. 2005). In Australia, they occur from Broome, Western Australia, north and east to the Brisbane River, Queensland. The range along the northern Australian coast and New Guinea is poorly documented (Parra et al. 2002).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Australian snubfin dolphins inhabit coastal, shallow waters and are most common in brackish estuaries. They have been seen in the same areas as Indo-Pacific humpback dolphins, which sometimes chase them aggressively. They occur most often near river and creek mouths, generally in waters less than 10 m deep (with a preference in some areas for very shallow waters, < 2 m deep) (Parra et al. 2006b)

Australian snubfin dolphins appear to be generalist feeders, taking a wide variety of fishes (including anchovies, sardines, eels, halibut, breams, grunters, and other estuarine species). They also eat cephalopods (squid, cuttlefish, and octopus), and crustaceans (shrimps and isopods, although the latter may be consumed incidentally).

Systems
  • Marine
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in coastal, brackish and fresh waters, tropical and subtropical
  • UNESCO-IOC Register of Marine Organisms
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Orcaella heinsohni

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

Download FASTA File
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Statistics of barcoding coverage: Orcaella heinsohni

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Specimens with Barcodes: 1
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
NT
Near Threatened

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Reeves, R.R., Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y. & Zhou, K.

Reviewer/s
Brownell Jr., R.L. & Cooke, J. (Cetacean Red List Authority)

Contributor/s

Justification
This species was described as separate from O. brevirostris only as recently as 2005. The available evidence supports the reasoning that there are fewer than 10,000 mature individuals and therefore the species meets the C criterion for Vulnerable in terms of population size. However, data are lacking to substantiate a continuing decline (C2). Similarly, no studies of population structure have been carried out so it is uncertain if either of the C2a subcriteria is met (i.e., whether no subpopulation is larger than 1000 mature, or all mature individuals are in a single subpopulation). Although the species could be listed as Data Deficient, Near Threatened is more appropriate given its limited range, low densities in surveyed areas, and its continuing vulnerability to bycatch. Rigorous, more extensive surveys are needed to support a reassessment of the species; it may then be found to qualify for listing as Vulnerable or possibly even Endangered.
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Population

Population
No overall population estimate is available for this species. There are only two abundance estimates for the Australian snubfin dolphin. Freeland and Bayliss (1989) roughly estimated that there were about 1,000 individuals in the Gulf of Carpentaria, Northern Territory, Australia. Their highest estimate was 1,227 individuals (CV=25%). However, the scientific credibility of that estimate has been challenged due to the difficulty of distinguishing Australian snubfin dolphins from other species during aerial surveys over turbid waters and later surveys conducted in the gulf that indicated a much lower population density (Parra et al. 2002; H. Marsh pers. comm). In Cleveland Bay, Queensland, abundance was estimated as < 100 (actual estimates ranged from 62-78, with CVs from 8-17%) (Parra 2005; Parra et al. 2006a). A survey conducted in May 2006 recorded only 15 groups totaling 88 animals distributed sparsely along portions of the northeastern part of the Kimberly coast (Debra Thiele pers. comm. to Brian Smith on 24 Jan 2007).

Although the species has been surveyed in only two areas (Cleveland Bay and Gulf of Carpentaria) which, together, comprise less than 20% of the species’ range, the results of those surveys, as well as the preliminary results from a reconnaissance survey of a portion of the Kimberly coast in 2006, indicate that the number of mature individuals is well below 10,000. It is assumed that the surveyed areas are broadly representative of the species’ density across its range. The population may be declining due to bycatch in commercial fishing nets (e.g. gillnets) and anti-shark nets.

Population Trend
Unknown
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Threats

Major Threats
The nearshore occurrence of this species makes it particularly vulnerable to human activities. However, most of its range in northern Australia and New Guinea has not been severely degraded. Substantial numbers of snubfin dolphins have been killed in anti-shark nets set to protect bathers (Paterson 1990). For example, in the Townsville region between 1968-1976, 15 of 24 dolphins known to have been killed were this species (Heinsohn 1979). The mortality rate of snubfin dolphins in anti-shark nets along the Queensland coast declined to an estimated 1.3/year between 1992-1995, coincident with the replacement of most anti-shark nets with baited drumlines (Gribble et al. 1998). In addition to the mortality in anti-shark nets, these dolphins die in inshore gillnets set across creeks, rivers and shallow estuaries primarily for barramundi (Lates calcarifer) and threadfin salmon (Polynemus sheridani) and (Eleutheronema tetradactylum) (Anderson 1995; Hale 1997).
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Management

Conservation Actions

Conservation Actions
The species is in Appendix I of CITES.

Regulations, including net attendance rules and gear modifications, have been introduced to reduce bycatch but enforcement, especially in remote areas, has been inadequate (Hale 1997). Some protection is believed to accrue to snubfin dolphins from their presence in dugong protection areas (Parra et al. 2002).
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Relevance to Humans and Ecosystems

Risks

IUCN Red List Category

Near Threatened (NT)
  • IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
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Wikipedia

Australian snubfin dolphin

The Australian snubfin dolphin (Orcaella heinsohni) is a dolphin found off the northern coasts of Australia. It closely resembles the Irrawaddy dolphin (of the same genus, Orcaella) and was not described as a separate species until 2005. The Australian snubfin has three, while the Irrawaddy dolphin only has two colours on its skin. The skull and the fins also show minor differences between the two species.

Taxonomy[edit]

Snubfin dolphin

The taxonomic specific name, heinsohni, was chosen in honor of George Heinsohn, an Australian biologist who worked at James Cook University, "for his pioneering work on northeast Australian odontocetes, including the collection and initial analysis of Orcaella heinsohni specimens which form the basis for much of our knowledge of the new species".[1]

New species of large mammals are quite rarely described nowadays, and those that are usually are from remote areas — such as the saola - or are otherwise rarely encountered, see for example Perrin's beaked whale, or the spade-toothed whale, which is only known from two complete specimens and a few bones cast ashore. In fact, the Australian snubfin was the first new dolphin species to be described in 56 years, but was followed, in 2011, by the discovery and description of the Burrunan dolphin (T. australis), also from the Australian continent. The Australian snubfin dolphin is unusual among recently described mammals in that a population is accessible for scientific study.

Nonetheless, the existence of snubfin dolphins in the waters of northern Australia had only become known in 1948, when a skull was found at Melville Bay (Gove Peninsula, Northern Territory). This individual apparently had been caught and eaten by aboriginals. However, the discovery remained unnoted until discussed by Johnson (1964), and soon thereafter a Dutch skipper had his observations of the then-unrecognized species published.[2]

Two scientists, Isabel Beasley of James Cook University and Peter Arnold of Museum of Tropical Queensland, took DNA samples from the population of dolphins off the coast of Townsville, Queensland, and sent them to the National Oceanic and Atmospheric Administration's Southwest Fisheries Science Center in La Jolla, California. The results showed George Heinsohn was correct in his hypothesis [3] that the Townsville population was a new species.

The holotype QM JM4721 (JUCU MM61) is the skull and some other bones of an adult male found drowned in a shark net at Horseshoe Bay, Queensland, on 21 April 1972. It was about 11 years old at the time of its death.[1]

Description[edit]

A species of delphinid in a genus, Orcaella, which contains one other species, the Irrawaddy dolphin Orcaella brevirostris, O. heinsohni is subtly tricoloured: brownish on the top, lighter brown along the sides, and a white belly; the Irrawaddy dolphin, on the other hand, is uniformly slate grey except for the white belly. The new species has a rounded forehead, very unlike other dolphin species in Australia, and the very small, "snubby" dorsal fin distinguishes it from other dolphins in its range. The lack of a groove on each side of the back and the presence of a neck crease further distinguishes this species from its relative.

Range and status[edit]

In the Pacific Ocean off Townsville, about 200 individual snubfin dolphins were found. The range of the species is expected to extend to Papua New Guinea; that is, O. heinsohni is endemic to the northern half of the Sahul Shelf, but the majority live in Australian waters. They are not thought to be common, and are being given a high conservation priority. Its IUCN classification of "data deficient" refers to this species and the Irrawaddy dolphin combined. [4] Threats include drowning in fishery and antishark nets; while some hunting by indigenous people probably occurs (as evidenced by the 1948 specimen), this is likely to be insignificant compared to the threat posed by drowning.

Conservation[edit]

The Australian snubfin dolphin is listed on Appendix II[5] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II[5] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.[6]

In addition, Australian snubfin dolphins are covered by Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).[7]

See also[edit]

Notes[edit]

  1. ^ a b Beasley, Robertson & Arnold 2005
  2. ^ Mörzer Bruyns 1966
  3. ^ Arnold and Heinsohn 1996
  4. ^ (Cetacean Specialist Group 1996).
  5. ^ a b "Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5th March 2009.
  6. ^ Convention on Migratory Species page on the Australian snubfin dolphin
  7. ^ Official webpage of the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region

References[edit]

  • Arnold, Peter W. & Heinsohn, George E. (1996): Phylogenetic status of the Irrawaddy dolphin Orcaella brevirostris (Owen in Gray): A cladistic analysis. Memoirs of the Queensland Museum 39(2): 141-204. HTML abstract
  • Beasley, Isabel; Robertson, Kelly M. & Arnold, Peter W. (2005): Description of a new dolphin, the Australian Snubfin Dolphin Orcaella heinsohni sp. n. (Cetacea, Delphinidae). Marine Mammal Science 21(3): 365-400. doi:10.1111/j.1748-7692.2005.tb01239.x (HTML abstract)
  • Johnson, D.P. (1964): Mammals of the Arnhem Land expedition. In: Specht, R.L. (ed.): Records of the American-Australian scientific expedition to Arnhem Land. Zoology: 427-515. Melbourne University Press, Melbourne, Australia.
  • Mörzer Bruyns, W.F.J. (1966): Some notes on the Irrawaddy dolphin, Orcaella brevirostris (Owen 1866). Zeitschrift fur Säugetierkunde 31: 367-372.
  • Reeves, R.R., Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y. & Zhou, K. (2008). Orcaella heinsohni. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 24 March 2009. Database entry includes a lengthy justification of why this species is listed as near threatened
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