Dugong (Dugong dugon) - endangered species listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Dugong, Dugong dugon (Müller 1776), as an ENDANGERED SPECIES on Part 1 of Schedule 1 of the Act. Listing of endangered species is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee found that:

1. The Dugong, Dugong dugon, is one of only four extant sirenian mammals. They are unique amongst marine mammals by being almost entirely herbivorous. The Dugongs main food is seagrass, and to a much lesser extent marine algae when seagrass is scarce. Individuals are known to occasionally take marine invertebrates such as mussels and tunicates (Heinsohn 1995). The species is long-lived (up to 70 years), relatively slow to attain sexual maturity (greater than nine years), and the interval between the birth of calves ranges from three to seven years (Heinsohn 1995).

2. The Dugong has a broad but disjunct distribution in tropical and subtropical shallow coastal waters of the Indian and Western Pacific Oceans (Smith 2001). The Australian Dugong population represents a stronghold for the species and possibly retains a majority of the global population. Resident populations are known from Shark Bay (Western Australia) along the north coast to Moreton Bay (Queensland). In New South Wales (NSW), visiting Dugongs have been recorded as far south as Twofold Bay, although the majority of records are for waters north of Jervis Bay (Smith 2001).

3. The Dugong does not breed in NSW, however habitat and resources within the state remain important to visiting individuals. Prior to 1992, only 14 Dugong records were known for NSW. A further 50 individuals, many of them dead, were recorded in NSW between 1992 and 1993. This influx of Dugongs to NSW waters coincided with a catastrophic loss of 1000km2 of seagrass from Hervey Bay (Queensland) after severe floods (Heinsohn 1995; Smith 2001). NSW waters act as a refuge area for Queensland's Dugongs.

4. The Dugong is threatened by coastal development and poor catchment management leading to siltation and the loss of seagrass beds. Isolated Dugong populations are vulnerable to local extinction as a result of losing seagrass beds after stochastic events such as floods or cyclones. The Dugong is also threatened by incidental mortality in commercial gillnets, entanglement in shark nets and collisions with boats (Smith 2001).

5. In view of the above points, the Scientific Committee is of the opinion that the Dugong, Dugong dugon, is likely to become endangered unless the circumstances and factors threatening its survival or evolutionary development cease to operate, and is therefore eligible for listing as an endangered species.

Proposed Gazettal date: 24/05/02
Exhibition period: 24/05/02 - 28/06/02

References 

Heinsohn, G.E. (1995). Dugong, Dugong dugon (Müller, 1776). In 'The Australian Museum Complete Book of Australian Mammals'. (Ed. R. Strahan.) pp. 668-70. (Reed Books: Chatswood, NSW.)

Smith, P. (2001). Review of the conservation status of marine mammals in New South Wales. Report to the NSW Scientific Committee.