|Scientific Name:||Euastacus crassus|
|Species Authority:||Riek, 1969|
|Red List Category & Criteria:||Endangered B1ab(iii) ver 3.1|
|Assessor/s:||Furse, J., Coughran, J. & Lawler, S.|
|Reviewer/s:||Collen, B. & Richman, N.|
|Contributor/s:||Livingston, F., Soulsby, A.-M., Batchelor, A., Dyer, E., Whitton, F., Milligan, HT, Smith, J., Lutz, M.L., De Silva, R., McGuinness, S., Kasthala, G., Jopling, B., Sullivan, K. & Cryer, G.|
Euastacus crassus has been assessed as Endangered B1ab(iii). This species has an estimated extent of occurrence of 4,500 km2, a severely fragmented distribution. The quality of this species habitat is compromised by the presence of exotic species which are assumed to be significantly impacting the long term viability of the population, as well as poor land management practices. The development of a hydroelectric dam has compromised the quality of habitat in part of this species range. Further research should be initiated to determine distribution and abundance, and determine key habitat parameters. Protection on instream and riparian habitat is required.
This species is endemic to Australia. It is present in the Australian Capital Territory, especially in the high country west of the Snowy Mountains and into the eastern semi-alpine country of Victoria as far as the Mount Beauty-Mount Hotham region (Morgan 1997). The range extends from northeast to southwest approximately 210 km (Morgan 1997). This species is restricted to the upper reaches of several drainages, and the range can thus be considered severely fragmented due to the isolating effects of unsuitable lowland habitat and the barriers of mountain ridges (Morgan 1997, Ponniah and Hughes 2006). It inhabits sites greater than 640 m above sea level. The range is extremely narrow, and the overall extent of occurrence (EOO) for the species is approximately 4,500 km² (J.M. Furse and J. Coughran pers. comm. 2008). The primary determinant of this species' distribution is elevation, so even within this EOO there will be places below 1,000 m where other crayfish species are found (S. Lawler pers. comm. 2008).
Native:Australia (Australian Capital Territory, Victoria)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||There is no population information available for this species. The species is considered rare (Van Praagh 2003, O'Brien 2007), although may be common in very localized situations (S. Lawler pers. comm. 2008).|
|Habitat and Ecology:||
This species typically occupies cool, clear upland streams in alpine and sub-alpine regions. In Morgan's (1997) description of the type locality, he describes an abundance of ferns, granitic substrate, with dry sclerophyll forest and heath. He also notes that this species has a patchy distribution in the Australian Capital Territory occurring in high streams where vegetation is relatively undisturbed.
The slow growth rate and low fecundity of many Euastacus renders them less resilient to reduction in population numbers through habitat destruction and catastrophic events (Van Praagh 2003).
Habitat modification is a major threat to this species. The habitat has been impacted by agriculture, burning, river regulation and in-stream structures (i.e., Snowy River Hydro-electric Scheme) (O'Brien 2007). Although this species occurs within national parks there are numerous other potential threats such as exotic fish and other exotic species, climate change, over-exploitation for food and bait (J.M. Furse and J. Coughran pers. comm. 2008).
Potentially large scale threats from exotic fishes such as Brown Trout, Rainbow Trout or Redfin Perch, which are prevalent throughout the region may impact this species (Davies and McDowall 1996, Rowe et al. 2008). 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), and could have localised impacts on this species by contributing to declines in distribution and/or local abundance.
Climate change, including increasing temperature, alterations to hydrological regimes, severe weather events, loss of suitable alpine habitat and increased potential for bushfires could pose a threat to this species (Chiew and McMahon 2002, Howden 2003, Hughes 2003, Pittock 2003, Hennessy 2006, Westoby and Burgman 2006, IPCC 2007). Due to the narrow thermal tolerance of this species, and its restricted range (restricted to cool, headwater streams in forested catchments), global temperature increase has resulted in range contraction. This species is further compromised by the presence of exotic species (goats, feral pigs, cats, foxes, trout and perch) which are known to predate on crayfish and degrade riparian habitat; while the precise effects of these threats on this species are not yet well understood, they are believed to be significantly impacting the long term viability of the population (J. Furse and J. Coughran pers. comm. 2010).
Within Victoria, this species is listed as threatened under The Flora and Fauna Guarantee Act 1988. The Scientific Advisory Committee determined that this species was particularly 'vulnerable' to future threats which are likely to result in extinction (Van Praagh 2003).
As a result of the action statement developed in 2003 by Van Praagh, the following actions were suggested: a) determine distribution and abundance of the species, b) protect instream and riparian habitat, c) determine key habitat parameters. Further research should also be initiated to include population assessment and monitoring, biological and life history information, investigations into thermal tolerance and resilience to exotic species.
In Victoria, a minimum recreational size limit of 90 mm OCL is in place for any spiny crayfish, and as this species does not attain that size, it is indirectly protected by this restriction. Apart from a ban on Euastacus armatus, there are no recreational fishing regulations for freshwater crayfish in the Australian Capital Territory (TAMS 2007).
|Citation:||Furse, J., Coughran, J. & Lawler, S. 2010. Euastacus crassus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 12 December 2013.|
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