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Astacopsis gouldi

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA ARTHROPODA MALACOSTRACA DECAPODA PARASTACIDAE

Scientific Name: Astacopsis gouldi
Species Authority: Clark, 1936
Common Name(s):
English Giant Freshwater Crayfish, Giant Tasmanian Lobster, Tasmanian Giant Freshwater Lobster

Assessment Information [top]

Red List Category & Criteria: Endangered A2ac ver 3.1
Year Published: 2010
Date Assessed: 2010-06-01
Assessor(s): Walsh, T. & Doran, N.
Reviewer(s): Collen, B. & Richman, N.
Contributor(s): Hamr, P., Soulsby, A.-M., Batchelor, A., Dyer, E., Whitton, F., Livingston, F., Milligan, H.T., Smith, J., Lutz, M.L., De Silva, R., McGuinness, S., Kasthala, G., Jopling, B., Sullivan, K. & Cryer, G.
Justification:
Astacopsis gouldi has been assessed as Endangered using Criteria A2ac. This species has seen a 70% decline within its range and an estimated 80% decline in abundance within the last 50 years (3 generation lengths). Due to its slow rate of maturity and reproductive age, any individuals, particularly males, which are removed from the system will have prolonged and damaging impacts upon the recruitment abilities of the subpopulation. This substantial decline in abundance and the habitat reduction and quality, would initially qualify this species for Critically Endangered using Criteria A. However, reintroductions are occurring in parts of this species range and these are proving successful, therefore the true rate of decline is likely to be between 50-70%. The northeastern part of its range has been dramatically impacted by mining with only two recorded stable subpopulations remaining. Much of the decline is attributed to illegal fishing pressure, past fishing pressure, and loss/ degradation of habitat as a result of deforestation. A species recovery plan has been devised but some crucial measures are yet to be implemented.
History:
1996 Endangered
1994 Indeterminate (Groombridge 1994)
1990 Vulnerable (IUCN 1990)
1988 Vulnerable (IUCN Conservation Monitoring Centre 1988)
1986 Vulnerable (IUCN Conservation Monitoring Centre 1986)

Geographic Range [top]

Range Description: This species is endemic to Tasmania, Australia. It is found in Tasmanian rivers flowing north into the Bass Strait (with the exception of the Tamar) between 20-300 m above sea level (T. Walsh pers. comm. 2008). Originally, populations were present in the Arthur River and all rivers flowing into Bass Strait, except those of the Tamar, but today the distribution is more broken (Inland Fisheries Service 2008). It has been introduced into two catchments: the North Esk catchment (St Patrick's River) and the Derwent catchment (Clyde River) (Threatened Species Section 2006). The extent of occurrence (EOO) of this species is estimated at 14,221 km².

Approximately 54% of the species' range occurs on unreserved private land, 24% on state forest (couped and uncouped), and 2% on other public land (e.g. unallocated Crown land, local council, etc). Approximately 19% of the species' range comprises either formal or informal reserves (Threatened Species Section 2006). It must be noted that the majority of this range held privately has been extensively modified (T. Walsh pers. comm. 2009). The best remaining habitat for this species is state forest and crown land (T. Walsh pers. comm. 2009).
Countries:
Native:
Australia (Tasmania)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population:

Based on condition of habitat, historical records and anecdotal reports, localized extinctions or large declines in numbers are thought to have occurred in the Welcome, Montagu, Rubicon, Don, Brid, Boobyalla, Pipers, Ringarooma, Duck, Little and Great Forester Rivers and Claytons Rivulet (Horwitz 1994).

Recent surveys in the north-east of this species' range indicated that massive population declines have occurred in these north-east catchments (Little Forester, Boobyalla-Tomahawk and  Ringarooma) and major population declines have occurred in Pipers and Great Forester/Brid catchments (T. Walsh pers. comm. 2008). Within this range, two small areas within these two catchments appear to have a stable population (T. Walsh pers. comm. 2008). These north-eastern populations have been too badly fragmented and are subject to substantial pressures such as broadscale plantation establishment and severe drying of streams (N. Doran pers. comm. 2009). This reduction of north-eastern ranges may equate to approximately one third of the total for this species. Recovery is, however, occurring in the north-west of the state (N. Doran pers. comm. 2009).

At sites that are relatively accessible to humans (close to roads), the proportion of mature individuals can be as low as 5% compared to 40% in relatively inaccessible sites (Hamr 1990). Walsh (pers. comm. 2008) estimates that there has been more than an 80% decline in this species abundance in the last 50 years, and has undergone a dramatic decline in 70% of its range. It has also been postulated that there may be increases in population abundance in catchment areas with relatively good habitat conditions, namely West to East Black Detention, Inglis, Cam, Emu, Blythe and Leven (T. Walsh pers. comm. 2008).



Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology:

This species can be found in rivers and streams of all sizes, but shows a preference for pristine habitats. It is most commonly found sheltering under decaying logs and undercut banks within deep pools, but is also seen moving through shallow riffle zones (Lynch 1967, Hamr 1990, Inland Fisheries Service 2008). Presence of relatively undisturbed riparian vegetation is another important factor determining the distribution of this species. Streams will also have excellent water quality and low turbidity (T. Walsh pers. comms. 2008). Absence of sediment has a massive influence on populations, and areas which have large amounts or increased levels of sedimentation are avoided by this species (T. Walsh pers. comm. 2008). Sites which had been completely cleared of riparian vegetation for agricultural land etc, showed an absence of this species. While the presence of native riparian vegetation is important to this species, it has also been occasionally found within pine plantations (Threatened Species Section 2006, T. Walsh pers. comm. 2008).

In terms of water chemistry, there is a noted preference for sites with a high oxygen content and little suspended sediment (Forteath 1987). This species has been found show a range of water temperatures from 5.2°C to 21°C (Hamr 1990, Lynch and Blühdorn 1997, Webb 2001), although relatively low temperatures are preferred (Threatened Species Section 2006). This species displays a shift in dietary preferences with age and typically feeds on decaying wood, rotting flesh, and small fish (T. Walsh pers. comm. 2008). 

Furthermore, this species displays a high degree of site fidelity. Studies in which mark and re-capture techniques have been applied, tracked this species moving distances of 500 m (Forteath 1987, Growns 1995) and 1650 m. (Webb 2001). Webb (2001) also noted the species returning to its home stream after movement.

Juvenile densities of this species are higher in wider streams at intermediate catchment sizes, typically 2 to 30 km²; streams with low levels of silt substrate (0-2%); streams with high proportions of moss cover (10% and above) and with higher proportions of boulder substrate (Davies and Cook 2004). These particular habitat requirements could have severe consequences for reproductivity if altered, as there could be a scenario where no juveniles are created due to poor habitat quality, resulting in a prolonged period of reduced population growth, until habitat conditions are improved (T. Walsh pers. comm. 2008).

Mating and spawning typically occurs in the autumn months post-summer moult, with females breeding every two years (Hamr 1990, 1992). However, recent studies have shown that females can release young and moult in the same year, meaning that they can potentially breed each year (Threatened Species Section 2006, Inland Fisheries Service 2008, T. Walsh pers. comm. 2008). Juveniles are released in the late summer and remain attached until February (T. Walsh pers. comms. 2008), and the number of eggs produced by a single female is said to be relative to body size (Hamr 1996). Males reach sexual maturity at nine years (T. Walsh pers. comm. 2008).

Systems: Freshwater

Use and Trade [top]

Use and Trade: This species is harvested at a local and national level as a food source.

Threats [top]

Major Threat(s):

The most significant threats facing this species is past fishing pressure, present illegal fishing, and habitat loss and degradation (Lynch 1967, Hamr 1990, Horwitz 1994, Growns 1995, Lynch and Blühdorn 1997). Under the Inland Fisheries Act 1995, the legal fishing of this species ceased as of January 1st 1998. While the relationship between fishing pressure and population dynamics, and structure, is not fully understood, decreases in average body size and the proportion of mature individuals present at accessible sites versus inaccessible sites, might indicate the negative impact that intense fishing pressure has had upon the population (Lynch and Blühdorn 1997, Hamr 1990). Of note is the effect which can be had by removing larger males who can, by their physical size, mate with large mature females (T. Walsh pers. comm. 2008). Since this fishing ban has been imposed, a notable increase in size has been observed in the population (T. Walsh pers. comm. 2008) The effects of fishing pressure on this species are further exacerbated by the slow maturation, low fecundity and biennially breeding cycle of this species. Furthermore, it has been suggested that it would take at least 15 years for juveniles to attain a size where the recruitment levels escalate considerably after the termination of fishing for this species (T. Walsh pers. comm. 2008). Despite an imposed law preventing the legal harvesting of this species, illegal fishing activity is still occurring throughout this species range as evidenced by baitlines, anecdotal reports and prosecutions (Threatened Species Section 2006). However, fishing pressure has decreased considerably, but due to this species' cumbersome size it is easy to catch and major damage can be inflicted by a few poachers in a short space of time (T. Walsh pers. comm. 2008).

Habitat loss and degradation is also a significant threat to this species. Due to its preference for relatively pristine sites, changes in land use and alterations to the hydrological regime of a river system are all likely to impact this species. Walsh (pers. comm. 2008) suggests that logging poses a greater risk to this species than harvesting. Large-scale, industrial logging activity throughout Tasmania has been implicated in sedimentation of waterways through the loss of sediment stability, resulting in increased turbidity and lower dissolved oxygen concentrations, along with unfavourable habitat for juveniles (Davies and Cook 2004). Loss of riparian zones can also result in increased run-off from surrounding land, decreased shading resulting in increased water temperatures, and decreased allochthonous material providing an important food source (T. Walsh pers. comm. 2008).

The Northwest region of this species' range is heavily impacted by agriculture and industry especially in areas 200 m and lower (T. Walsh pers. comm. 2008). A massive old tin mine sits on the headwaters of Arthur River, where it is estimated that the population of this species has been extirpated for up to 20 km, due to heavy metals still flushing from the mine. A large creek pours from the mine into the Arthur River with a pH of less than 3 (T. Walsh pers. comm. 2008). Other threats associated with forestry activities include: chemical spraying, roading and culverts, with the latter presenting a barrier to effective dispersal. This species is also potentially impacted by the effects of climate change by increased aridity causing streams to dry up and by farmers increasing water extraction for irrigation especially in the northeastern region (T. Walsh pers. comm. 2008).

Conservation Actions [top]

Conservation Actions:

This species has received much attention as a species of conservation concern. In 1995 it was listed as 'Vulnerable' under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (and preceding legislation) and also under the Tasmanian Threatened Species Protection Act 1995 (N. Doran pers. comm. 2009). Under the Tasmanian regional assessment process, it was identified as a category three fauna species i.e. requiring conservation through management plans (PLUC 1997). It was then subsequently listed as a 'priority species requiring consideration' under the Tasmanian RegionalForest Agreement 1997 and thereby protected through the Comprehensive, Adequate and Representative (CAR) Reserve System. However, after 11 years there has not been one area specifically reserved for this species, even though there have been at least three reports, documenting the stable population areas remaining (T. Walsh pers. comm. 2008). It has been calculated that 30,000 ha would be sufficient to protect the best remaining tracts of habitat (T.Walsh pers. comm. 2008).

Management of this species is primarily governed by the Threatened Species Unit, which introduced the ban upon the harvesting, trade or keeping of this species without a permit since the 1st of January 1998 (T. Walsh pers. comm. 2008).  A large portion of the range of this species falls within the South West Wilderness World Heritage Area, and so the species is free of many of the other land use pressures (and a lot of poaching) over a lot of its range (T. Walsh pers. comm. 2008). Though, in this species' northeastern range, there still is no protection other than a 10 m machinery exclusion zone for and waterways above 250 m. The Recovery Plan has an attachment stating what can be classified as suitable habitat, though only below 250 m above sea level. Most forest operations would occur above 250 m, as below this altitude the forests have predominately been cleared (T. Walsh pers. comm. 2008). However, due to stream classification requirements, small streams are not protected by buffer zones and headwater areas are not given buffers because not many crayfish are located in there (T. Walsh pers. comm. 2008).

Recovery is primarily occurring in the northwest of Tasmania, while populations in the northeast appear to have been too badly fragmented and subject to substantial pressures: i.e. broadscale plantation establishment and severe drying of streams (N. Doran pers. comm. 2009).

In response to the widespread dramatic declines seen in this species' population abundance, a recovery plan has been developed to see the species down listed from 'Vulnerable' within the next 14 years. The following strategies have been proposed: 1) reduction in fishing pressure, 2) prevention and amelioration of the effects of habitat disturbance, 3) monitoring of population recovery, and identification and protection of core populations, 4) increasing knowledge of the species' biology and habitat requirements and 5) overall coordination of the recovery process. Integration of local communities within the recovery strategies is going to be necessary, to ensure the success of the project (Threatened Species Section 2006). Protection and rehabilitation of riparian buffer strips adjacent to high habitat suitability sites (Davies and Cook 2004) is imperative to ensure the continued viability of these populations.


Citation: Walsh, T. & Doran, N. 2010. Astacopsis gouldi. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 30 July 2014.
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