|Scientific Name:||Euastacus diversus|
|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., 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.|
Euastacus diversus has been assessed as Endangered under criterion B1ab(iii). It is endemic to Australia, and has been found at only seven localities in Victoria. This species' has an extremely fragmented distribution with an extent of occurrence of approximately 500 km2. There is a continuing decline in the quality of this species' habitat as a result of timber harvesting, and sedimentation caused by nearby roads and roadworks. This decline in habitat quality is resulting in further loss of suitable habitat in surrounding areas. Linear reserves have been established in areas where this species has been identified, but it is not yet known what proportion of the population is protected by these. Monitoring of implemented conservation measures is needed to determine how effective they are at mitigating identified threats. It is foreseeable that future assessments will place this species in higher threat categories when further information on its population status (i.e. declines), genetics and thermal tolerance becomes available.
This species is endemic to Australia. It has a very restricted distribution, having been found at only seven localities on, and around the Erinundra Plateau in East Gippsland, Victoria. The type locality is approximately 50 km north of Orbost (Morgan 1986). The species was then rediscovered in Ferntree, Ellery, Jungle and Lilly-Pilly Creeks, all in the headwaters of the Brodribb River (J. M. Furse and J. Coughran pers. comm. 2008). In 1995 a subpopulation was located in Yandown Creek, in the headwaters of the Queensborough River. This is the only subpopulation known outside the Brodribb River Catchment (Murray 2003). The terrain is rugged, and its restriction to headwater streams at elevations between 350 - 1,050 m above sea level warrants that the distribution of this species be considered as highly fragmented (Morgan 1997, Ponniah and Hughes 2006). The extent of occurrence of this species is estimated at approximately 500 km2 (J.M. Furse and J. Coughran pers. comm. 2008).
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The species was considered rare by Horwitz (1990), and is still uncommon at the sites it inhabits. Some of these sites are also inhabited by the larger and dominant E. kershawi (Coughran 2008 unpublished data). This species is common enough at the site 30 miles north of Orbost, with several caught within a few minutes (S. Lawler pers. comm. 2008).|
|Habitat and Ecology:||The habitat and ecology of this species is not well known. However, the streams present within its range are cool, perennial and highly oxygenated, flowing through wet or damp forest or rainforest. The substrate is usually cobbles, pebbles, or gravel and there is an abundance of instream debris (Murray 2003).|
This species faces various serious threats associated with land use management and ongoing forestry practices within its limited range (Murray 2003). These threats include increased sedimentation of waterways from construction of logging roads, clear felling of vegetation, and associated prescribed burning for vegetation regeneration purposes (Murray 2003). In addition, stream flow regimes and various water quality parameters (i.e. temperature, organic material and nutrient loads, and oxygenation levels) are likely to be influenced by land use practices within its small range (Murray 2003). These threats are likely to become more pronounced as the logging activities encroach on waterways inhabited by this crayfish (J. M. Furse and J. Coughran pers. comm. 2008). As a result, timber harvesting and burning of the forest to manage timber is the largest threat to this species with its entire distribution in a logging zone (S. Lawler pers. comm. 2008).
Localised catastrophic events, such as a prolonged drought or large sediment pulses could drastically affect populations of this species. Roads alongside, or across, streams are the most likely source of a sediment pulse. Road works can also cause an increase in sedimentation immediately downstream of the works, causing a decline in the quality of both the water and the substrate (Murray 2003).
As a high altitude species, climate change poses a threat, including increased temperature, alterations to hydrological regimes, severe weather events, loss of suitable highland habitat and increased potential for bushfires (Chiew and McMahon 2002, Howden 2003, Hughes 2003, Pittock 2003, Hennessy 2006, Westoby and Burgman 2006, IPCC 2007).
Exotic species (cats, foxes, pigs, goats, brown trout) that have generally been found to impact on crayfish (Green and Osbourne 1981, Horwitz 1990, Merrick 1995, Eyre et al. 1997, Murray 2003, ACT Government 2007, O'Brien 2007) also occur in this species' range (DEH 2004a,c,d,e), and given this species restricted distribution and apparent rarity, could have serious impacts on this species by contributing to declines in distribution and/or local abundance (J. M. Furse and J. Coughran pers. comm. 2008).
There are currently no conservation measures in place for this species, however in Victoria, a minimum recreational fishing size of 90 mm Orbital Carapace Length applies (DPI 2007); as this species does not attain that size, it is indirectly protected by this restriction.
There are plans to establish some protected habitat areas at sites where E. diversus has been recorded. If implemented these will be Linear Reserves consisting of an undisturbed buffer of approximately 100 m on each bank of the stream 1 km upstream and downstream of sites where E. diversus were recorded (Murray 2003). Land use management practices will apparently be managed or restricted within and nearby these Linear Reserves (i.e. no road construction, and any fuel reduction or regeneration burning in the vicinity will be strictly controlled to ensure that the reserves themselves are not burnt (Murray 2003)).
When established these protected habitat areas should be monitored to evaluate the efficacy of the threat mitigation measures implemented therein. Existing populations should also be monitored to identify if any dramatic decreases in numbers occur. Research should be initiated to include population assessment and monitoring, biological and life history information, habitat requirements, population genetics, investigations into thermal tolerance and resilience to exotic species.
|Citation:||Furse, J., Coughran, J. & Lawler, S. 2010. Euastacus diversus. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 06 July 2015.|
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