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Euastacus dharawalus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA ARTHROPODA MALACOSTRACA DECAPODA PARASTACIDAE

Scientific Name: Euastacus dharawalus
Species Authority: Morgan, 1997
Taxonomic Notes:

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(iii,v) ver 3.1
Year Published: 2010
Date Assessed: 2010-06-01
Assessor(s): Furse, J. & Coughran, J.
Reviewer(s): Collen, B. & Richman, N.
Contributor(s): Livingston, F., Livingston, F., Soulsby, A.-M., Batchelor, A., Dyer, E., Whitton, F., Milligan, H.T., Smith, J., Lutz, M.L., De Silva, R., McGuinness, S., Kasthala, G., Jopling, B., Sullivan, K. & Cryer, G.
Justification:
Euastacus dharawalus has been assessed as Critically Endangered under criterion B1ab(iii,v). This species has an extent of occurrence of approximately 80 km2 and is known from a single location. A continuing decline has been observed in both its quality of habitat and the number of mature individuals. These declines are attributed to tourism, fishing, alterations in the hydrological regime of headwater streams, and competition from the non-native species Cherax destructor. A recent survey collected few individuals which were in poor condition. Urgent action is required to prevent further harvesting of this species and minimise further spread of non-native species. This species faces a very real risk of extinction in the wild within the near future.

Geographic Range [top]

Range Description:

This species is endemic to Australia. It is known only from a small area in and near the northern section of Morton National Park, southwest of Robertson, New South Wales which is drained by tributaries of the Kangaroo and the Shoalhaven rivers (Morgan 1997). This species was collected in 1981 from only a single site, to the north east of Fitzroy Falls from where most specimens have been collected. The extent of occurrence is approximately 80 km2 (J.M. Furse and J. Coughran).

Countries:
Native:
Australia (New South Wales)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population:

There are no population data available for this species, although the species appears to be rare. The species is considered to be in rapid decline due to several factors such as habitat clearing and water impoundment (J.M. Furse and J. Coughran pers. comm. 2008).

Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology:

This species is found in areas with some Eucalypts along the stream banks. They inhabit burrows in the soft stream bed (Morgan 1997). The site at which this species was found has been largely cleared of Eucalypts (Morgan 1997).

Systems: Freshwater

Threats [top]

Major Threat(s): The species is restricted to a small plateau above a steep cliff. The overall stream length is in the order of a few kilometres, and has been altered dramatically by the establishment of a water impoundment. An exotic crayfish species, Cherax destructor, has invaded the stream (likely after being deliberately stocked in the impoundment). This exotic crayfish is aggressive and far more prolific and faster growing than Euastacus dharawalus. As such, it may outcompete the native species in a short period of time. An exotic species of trout also occurs in the stream which is likely to further impact the native species (Horwitz 1990; Merrick 1995). The area is within a National Park, adjacent to a well developed information centre and picnic area that receives heavy tourist traffic. The area appears to be heavily fished by recreational fishers, and this fishing pressure is likely to be having a major impact on the species, particularly in light of the competition from the invading Cherax destructor. A recent hour-long survey (Coughran 2008 unpublished data) collected only three E. dharawalus and 75 (5kg) of exotic Cherax destructor. All three E. dharawalus specimens were heavily wounded.

Other exotic species (cats, foxes, pigs, goats) that have generally been found to impact on crayfish (e.g. Green and Osbourne 1981; Horwitz 1990; Merrick 1995; Eyre et al. 1997; ACT Government 2007; O’Brien 2007) also occur in this species’ range (DEH 2004a,b,c,d). These exotic species could have additional impacts on E. dharawalus which given its highly restricted distribution, and other known threats, could exacerbate the current rapid decline in abundance.

Conservation Actions [top]

Conservation Actions:

There are no species specific conservation measures in place for this species. Research should be urgently initiated to include population assessment and monitoring, biological and life history information, habitat requirements, investigations into thermal tolerance and resilience to exotic species. A captive breeding program should also be considered.

In New South Wales, a minimum recreational size limit of 90mm OCL is in place for any spiny crayfish (NSW DPI 2007). Euastacus dharawalus does not attain that size, and so is indirectly protected by this restriction. However, the site is a popular tourist recreational spot, and there are signs of heavy crayfishing activity (e.g. claws in the carparks and around picnic tables). Given that the introduced Cherax species is more prolific and faster growing, it is predicted that recreational fishing pressure will exacerbate the on-going competition between the exotic and native species.


Citation: Furse, J. & Coughran, J. 2010. Euastacus dharawalus. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 24 October 2014.
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