Biodiversity

Species Profile and Threats Database


For information to assist proponents in referral, environmental assessments and compliance issues, refer to the Policy Statements and Guidelines (where available), the Conservation Advice (where available) or the Listing Advice (where available).
 
In addition, proponents and land managers should refer to the Recovery Plan (where available) or the Conservation Advice (where available) for recovery, mitigation and conservation information.

EPBC Act Listing Status Listed as Critically Endangered
Listing and Conservation Advices Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
 
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
 
Recovery Plan Decision Recovery Plan not required, "the approved conservation advice for the species now provides sufficient direction to implement priority actions and mitigate against key threats. Further actions are being implemented as described in the Western Australian Department of Environment and Conservation's 'Dunsborough Burrowing Crayfish (Engaewa reducta), Margaret River Burrowing Crayfish (Engaewa pseudoreducta) and Walpole Burrowing Crayfish (Engaewa walpolea) Recovery Plan 2007-2016. Interim Recovery Plan No. 41' (14/04/2009)".
 
Adopted/Made Recovery Plans
Federal Register of
    Legislative Instruments
Inclusion of species in the list of threatened species under section 178 of the Environment Protection and Biodiversity Conservation Act 1999 (79) (14/04/2009) (Commonwealth of Australia, 2009n) [Legislative Instrument].
 
State Government
    Documents and Websites
WA:Draft Dunsborough Burrowing Crayfish (Engaewa reducta), Margaret River Burrowing Crayfish (Engaewa pseudoreducta) and Walpole Burrowing Crayfish (Engaew walpolea) Recovery Plan 2007-2016 (Western Australian Department of Environment and Conservation (WA DEC), 2008a) [State Recovery Plan].
State Listing Status
WA: Listed as Endangered (Wildlife Conservation Act 1950 (Western Australia): September 2013 list)
Non-statutory Listing Status
IUCN: Listed as Endangered (Global Status: IUCN Red List of Threatened Species: 2013.1 list)
Scientific name Engaewa reducta [82675]
Family Parastacidae:Decapoda:Malacostraca:Arthropoda:Animalia
Species author Riek, 1967
Infraspecies author  
Reference Riek, E.F. 1967 Australian Journal of Zoology 15: 103-121 [108 fig. 3]
Distribution map Species Distribution Map

This is an indicative distribution map of the present distribution of the species based on best available knowledge. See map caveat for more information.

Illustrations Google Images

The current conservation status of the Dunsborough Burrowing Crayfish, Engaewa reducta, under Australian and State Government legislation, is as follows:

National: Listed as Critically Endangered under the Environmental Protection and Biodiversity Conservation Act 1999.

Western Australia: Listed as Endangered under the Wildlife Conservation Act 1950.

Scientific name: Engaewa reducta

Common Name: Dunsborough Burrowing Crayfish

The taxonomic status of the Walpole Burrowing Crayfish is conventionally accepted (Horwitz & Adams 2000).

The Dunsborough Burrowing Crayfish is a small burrowing crayfish up to 50 mm in length. It generally has a pale to mid-brown colour with purplish-blue claws. The narrow abdomen is often shorter than the head and thorax. Other distinguishing features are the reduced eye size, large claws adapted to digging, and the way that the fingers of the claws move in a vertical plane.

The Dunsborough Burrowing Crayfish is almost identical in appearance to closely related species such as the Margaret River Burrowing Crayfish (E. pseudoreducta) and the Walpole Burrowing Crayfish (E. walpolea). Identification of the individual species can be determined by examining anatomical features using a microscope. Dunsborough Burrowing Crayfish can be distinguished by the presence of low, short rostral carinae (raised ridges on the pointed rostrum at the front of the head), which are absent in other Engaewa species, and the presence of pits or pores on the lateral processes (side projections) of the third and fourth pereopods (walking legs). In the field, these species are more easily distinguished from each other by the river system in which they are found, as they have extremely limited capacity for dispersal and are geographically isolated (Horwitz & Adams 2000).

The Dunsborough Burrowing Crayfish is endemic to south-western Western Australia and is known from an area between Dunsborough and the Margaret River, approximately 250 km south of Perth. Past surveys within the known range of the Dunsborough Burrowing Crayfish have collected the species at 13 different locations. The species is now considered extinct at one location, and a further three locations have not been resurveyed since 1995. The remaining nine locations were resurveyed in 2007 and contain extant populations. The majority of these nine locations are on private property, with three locations receiving limited protection in reserves, however the perpetuity of these reserves is not assured (TSSC 2009i).

The extent of occurrence of the Dunsborough Burrowing Crayfish has been estimated at approximately 108 km² based on the area encompassed by all known sites (WA DEC 2008a).

The species' area of occupancy is estimated at 6 km² based on the area of remnant vegetation associated with swamps and drainage lines. The species occurs in the South West Natural Resource Management Region (WA DEC 2008a).

All known Dunsborough Burrowing Crayfish sites are located on the Busselton Shire Boundary, bound by the Carbunup River to the east and the Leeuwin-Naturaliste Ridge to the west. They are all located in the headwater seepage/swamp areas of drainage systems that flow north into the Carbunup River, Mary Brook and Station Gully, or directly into Geographe Bay (WA DEC 2008a).

The species' distribution is severely fragmented in the northern Capes area. Land clearing of the swamps for agriculture, dam construction, water extraction and sand mining have all contributed significantly to reducing the area of its occupancy (WA DEC 2008a).

Past surveys within the known range of the Dunsborough Burrowing Crayfish have collected the species at 13 different locations. The species is now considered extinct at one location, and a further three locations have not been resurveyed since 1995. The remaining nine locations were resurveyed in 2007 and contain extant populations (TSSC 2009i).

There are no population estimates for the Dunsborough Burrowing Crayfish, though numbers are likely to be low based on the highly restricted area of occupancy.

The generation length of the Dunsborough Burrowing Crayfish is unknown, however, they are considered to be long-lived with slow maturation (WA DEC 2008a).

The Dunsborough Burrowing Crayfish is poorly represented in the reserve system, with Haag Nature Reserve and the proposed Yelverton Forest Conservation area the only Western Australian Department of Environment and Conservation (WA DEC) managed lands containing populations. The Haag Nature Reserve is only 0.09 km² in size but is considered the current stronghold for the species. A museum record from 1976 falls within the Yelverton National Park boundary but the exact location is uncertain and the existence of the population has yet to be reconfirmed (WA DEC 2008a). The majority of populations are located on private property, however, a number of properties identified as containing populations, are owned by registrants with the Land for Wildlife program or have conservation convenants over the land (WA DEC 2008a).

The Dunsborough Burrowing Crayfish uses a variety of habitats that provide moist sandy/loamy soils and an accessible watertable. These include vegetated seepages, swamp plains and swampy headwaters of streams.

Vegetation associated with these habitats is usually very dense native heaths dominated by myrtaceous shrubs and the soils have a high sand content (Burnaham 2005; Burnham et al. 2007).

The lifespan and age at sexual maturity for Western Australian burrowing crayfish species are unknown but they are thought to be long-lived (WA DEC 2008a).

No egg-carrying specimens of the Dunsborough Burrowing Crayfish have been collected, however, the maximum recorded egg-count for the closely related Engaewa similis is 25 (Horwitz & Adams 2000).

The Dunsborough Burrowing Crayfish is difficult to study in the wild and details of diet and reproduction are not known. Other burrowing freshwater crayfish are believed to eat rotting wood, detritus, root material and occasionally animal material (Bryant & Jackson 1999b; Growns & Richardson 1988; Suter & Richardson 1977).

Engaewa spp. may surface in extremely wet conditions, when watertables are rising and shallow surface water is present. This phenomenon is rare, and may be related to mate-searching and reproduction or avoidance of high groundwater levels and floodwaters (WA DEC 2008a).

Microscopic examination of the Dunsborough Burrowing Crayfish is usually required to detect the low, short rostral carinae (raised ridges on the pointed rostrum at the front of the head), which are absent in other Engaewa species, and the presence of pits or pores on the lateral processes (side projections) of the third and fourth pereopods (walking legs). However they are difficult to detect in the wild because of their complex burrow system which can be several metres deep and which may extend down to the freshwater watertable in drier months. At wetter times of the year burrows are marked by conspicuous chimneys of soil pellets (TSSC 2009i).

The main threat to the Dunsborough Burrowing Crayfish has been habitat loss and destruction caused by anthropogenic disturbance within the species' range. Land clearing for agriculture and forestry has removed habitat for the species. Farm dam construction has flooded suitable habitat and thus altered surface water and groundwater flows. Cattle grazing has physically destroyed burrows through trampling and soil compaction, has created serious erosion and has impaired soil permeability and water holding capacity (Burnham 2005; Burnham et al. 2007). These processes have led to the extinction of one population and have likely led to other unrecorded, localised population extinctions (WA DEC 2008a).

Potential threats to the Dunsborough River Burrowing Crayfish include drainage for peat, sand mining or agriculture activities, which can desiccate the species' moisture-rich habitats; and water extraction from bores, which can lower water tables and potentially cause acidification and mobilisation of toxic metal ions in wetlands (WA DEC 2008a).

Feral pigs (Sus scrofa) may damage habitat through ground-rooting feeding behaviour and directly prey on crayfish during rare surfacing events. Feral pig numbers are increasing in south-western Western Australia due to illegal introductions by recreational pig hunters and the subsequent reproductive success of the feral pigs (Spencer & Hampton 2005)

The impact of fire on the Dunsborough Burrowing Crayfish has not been investigated, but fire can severely damage swamp habitats (WA DEC 2008a). It is suggested that, whilst not directly threatening individual Dunsborough Burrowing Crayfish, burning may destroy the organic content, structure and water holding capabilities of soils found in those habitats, making it more prone to future fires and thus less suitable for the species through acidification and metal toxification. Fire fighting techniques could also be detrimental to a species with such a restricted distribution (WA DEC 2008a).

A further threat that has not been quantified but may be detrimental to the Dunsborough Burrowing Crayfish is disease from introduced crayfish species (Burnham 2005; Burnham et al. 2007).

Minister's reasons for recovery plan decision

The approved conservation advice for the species now provides sufficient direction to implement priority actions and mitigate against key threats. Further actions are being implemented as described in the Western Australian Department of Environment and Conservation's 'Dunsborough Burrowing Crayfish (Engaewa reducta), Margaret River Burrowing Crayfish (Engawea pseudoreducta) and Walpole Burrowing Crayfish (Engaewa walpolea) Recovery Plan 2007-2016. Interim Recovery Plan No. 41'.

A nationally adopted recovery plan is not considered to be necessary at this time.

Other recovery actions

The draft Dunsborough Burrowing Crayfish (Engaewa reducta), Margaret River Burrowing Crayfish (Engaewa pseudoreducta) and Walpole Burrowing Crayfish (Engaew walpolea) Recovery Plan 2007-2010 (WA DEC 2008a) outlines the following recovery objectives for these species:

  • Determine the current distribution and identify additional populations of Engaewa.
  • Increase public awareness and participation in threatened species protection.
  • Protect habitat.
  • Improve knowledge of Engaewa life history and ecology.

The Conservation Advice for the Dunsborough River Burrowing Crayfish (TSSC 2009i) outlines research priorities and priority actions for the protection of the species. These include:

  • Research the species life history (longevity, dispersal, reproduction).
  • Research the species ability to withstand desiccation, acidity and low dissolved oxygen levels and effects of fire.
  • Design and implement a monitoring program, including improved ways of catching and releasing animals for study (currently animals must be dug out by hand).
  • Undertake survey work in suitable habitat and potential habitat to locate any additional populations/occurrences.
  • Monitor known populations to identify key threats.
  • Monitor the progress of recovery, including the effectiveness of management actions and the need to adapt them if necessary.
  • Minimise adverse impacts from land use at known sites, particularly agriculture and forestry operations.
  • Manage any disruptions to water flows to minimise impact on surface water and groundwater flows such as farm dam construction, drainage activities, agricultural, forestry or mining operations, or groundwater extraction.
  • Manage known sites to prevent introduction of invasive weeds, which could become a threat to the Dunsborough Burrowing Crayfish, using appropriate methods.
  • Prevent habitat degradation/destruction by cattle and sheep grazing at known sites.
  • Manage feral pigs at known sites to minimise impacts from ground-rooting and wallowing.
  • Manage feral pigs at known sites to minimise impacts from predation.
  • Implement an appropriate fire regime for the habitat of local populations.

The following documents may inform the conservation of this species:

  • Draft Dunsborough Burrowing Crayfish (Engaewa reducta), Margaret River Burrowing Crayfish (Engaewa pseudoreducta) and Walpole Burrowing Crayfish (Engaew walpolea) Recovery Plan 2007-2010 (WA DEC 2008a).
  • The Conservation Advice for the Dunsborough River Burrowing Crayfish (TSSC 2009i).

The following table lists known and perceived threats to this species. Threats are based on the International Union for Conservation of Nature and Natural Resources (IUCN) threat classification version 1.1.

Threat Class Threatening Species References
Agriculture and Aquaculture:Agriculture and Aquaculture:Land clearing, habitat fragmentation and/or habitat degradation Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Agriculture and Aquaculture:Livestock Farming and Grazing:Habitat alteration (vegetation, soil, hydrology) due to trampling and grazing by livestock Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Biological Resource Use:Hunting and Collecting Terrestrial Animals:Harvesting for recreational purposes Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Biological Resource Use:Logging and Wood Harvesting:Habitat loss, modification and degradation due to timber harvesting Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Climate Change and Severe Weather:Habitat Shifting and Alteration:Habitat modification, destruction and alteration due to changes in land use patterns Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Ecosystem/Community Stresses:Indirect Ecosystem Effects:Restricted geographical distribution (area of occupancy and extent of occurrence) Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Energy Production and Mining:Mining and Quarrying:Habitat modification through open cut mining/quarrying activities Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Grazing, tramping, competition and/or habitat degradation Sus scrofa (Pig) Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Invasive and Other Problematic Species and Genes:Invasive and Other Problematic Species and Genes:Presence of pathogens and resulting disease Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Natural System Modifications:Dams and Water Management/Use:Alteration of hydrological regimes and water quality Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Natural System Modifications:Dams and Water Management/Use:Changes in hydrology including habitat drainage Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Natural System Modifications:Dams and Water Management/Use:Changes to hydrology including construction of dams/barriers Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Natural System Modifications:Dams and Water Management/Use:Extraction of ground water Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Natural System Modifications:Fire and Fire Suppression:Inappropriate and/or changed fire regimes (frequency, timing, intensity) Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Pollution:Agricultural Effluents:Herbicide application Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Pollution:Agricultural Effluents:Pesticide application Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Pollution:Pollution:Acid sulphate soils Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Pollution:Pollution:Habitat degradation and loss of water quality due to salinity, siltaton, nutrification and/or pollution Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Pollution:Pollution:Pestitcide application and runoff Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].
Transportation and Service Corridors:Roads and Railroads:Development and/or maintenance of roads Commonwealth Conservation Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009i) [Conservation Advice].
Transportation and Service Corridors:Roads and Railroads:Development of roads and railroads Commonwealth Listing Advice on Engaewa reducta (Threatened Species Scientific Committee (TSSC), 2009l) [Listing Advice].

Bryant, S. & J. Jackson (1999b). Tasmania's Threatened Fauna Handbook: What, Where and How to Protect Tasmania's Threatened Animals. Hobart, Tasmania: Threatened Species Unit, Parks and Wildlife Service.

Burnham, Q.F. (2005). The systematics of the reducta complex of the burrowing freshwater crayfish Engaewa Riek. Hons. Thesis. Perth: Edith Cowan University.

Burnham, Q.F., A. Koenders & P. Horwitz (2007). Field studies into the biology and conservation requirements of Engaewa species in the South-West and Warren DEC Regions. Final Report Prepared for Department of Environment and Conservation 30 November 2007.

Growns, I.O. & A.M.M. Richardson (1988). The diet and burrowing habits of the freshwater crayfish Parastacoides tasmanicus tasmanicus Clark (Decapoda: Parastacidae). Australian Journal of Marine and Freshwater Research. 39:525-534.

Horwitz, P. & M. Adams (2000). The systematics, biogeography and conservation status of the species in the freshwater crayfish genus Engaewa Riek (Decapoda: Parastacidae) from south-western Australia. Invertebrate Taxonomy. 14:655-680.

Spencer, P.B.S. & J.O. Hampton (2005). Illegal translocation and genetic structure of feral pigs in Western Australia. Journal of Wildlife Management. 69:377-384.

Suter, P.J. & A.M.M. Richardson (1977). The biology of two species of Engaeus (Decapoda: Parastacidae) Tasmania. III. Habitat, food, associated fauna and distribution. Australian Journal of Marine and Freshwater Research. 28:95-103.

Threatened Species Scientific Committee (TSSC) (2009i). Commonwealth Conservation Advice on Engaewa reducta. [Online]. Department of the Environment, Water, Heritage and the Arts. Available from: http://www.environment.gov.au/biodiversity/threatened/species/pubs/82675-conservation-advice.pdf.

Western Australian Department of Environment and Conservation (WA DEC) (2008a). Draft Dunsborough Burrowing Crayfish (Engaewa reducta), Margaret River Burrowing Crayfish (Engaewa pseudoreducta) and Walpole Burrowing Crayfish (Engaew walpolea) Recovery Plan 2007-2016. [Online]. Western Australia: Department of Environment and Conservation. Available from: http://www.dec.wa.gov.au/pdf/plants_animals/threatened_species/frps/41-burrowing-crayfish-recovery-plan-01feb2009.pdf.

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This database is designed to provide statutory, biological and ecological information on species and ecological communities, migratory species, marine species, and species and species products subject to international trade and commercial use protected under the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act). It has been compiled from a range of sources including listing advice, recovery plans, published literature and individual experts. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. Individuals and organisations should consider all the available information, including that available from other sources, in deciding whether there is a need to make a referral or apply for a permit or exemption under the EPBC Act.

Citation: Department of the Environment (2014). Engaewa reducta in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Sun, 13 Jul 2014 13:13:26 +1000.