Giant freshwater crayfish (Astacopsis gouldi)

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Giant freshwater crayfish
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Giant freshwater crayfish fact file

Giant freshwater crayfish description

KingdomAnimalia
PhylumArthropoda
ClassCrustacea
OrderDecapoda
FamilyParastacidae
GenusAstacopsis (1)

This magnificent crayfish is the largest known freshwater invertebrate and has particularly powerful pincers (2). They range in colour, according to habitat and location, from dull brown to greeny-black, but can have steely blue sides, or be dazzling blue all over (4).

Size
Length: 40 cm (2)
Weight
2 – 3 kg (2)
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Giant freshwater crayfish biology

The giant freshwater crayfish is a mere 6 mm long as a hatchling, and matures extremely slowly, living for up to 40 years (5). Reproductive maturity occurs at around nine years in males and 14 years in females, with females breeding just once every two years (2). Mating occurs in autumn and the eggs, attached to the female’s swimming legs during development, hatch the following summer, remaining attached to the swimming legs as hatchlings for another month. Such a long reproductive process means that females spend much of their life with their young attached to their legs – a good strategy as fully grown adults have no natural predators (2). However, fishing of adult crayfish by humans results in the removal of not only the adults but all their young as well (3).

The giant freshwater crayfish is omnivorous, eating primarily rotting wood and animal flesh, as well as leaves and insects that fall into the water. Juveniles tend to hide in shallow water where they are less at risk from their large predators including fish and platypuses. Adults hide under submerged logs in deep pools where they appear to tolerate each other, despite being aggressive elsewhere (5).

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Giant freshwater crayfish range

The giant freshwater crayfish was previously found in all rivers that flow into the Bass Strait, which runs between Tasmania and the Australian mainland. Today, however, the distribution is patchy and limited to less disturbed areas (3).

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Giant freshwater crayfish habitat

These crustaceans inhabit dark, slow-moving rivers and streams with high water quality and little suspended sediment, as well as still, deep pools with logs and overhanging banks to shelter beneath (2) (3) (4). The water needs to be below 18 oC with high oxygen content (5).

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Giant freshwater crayfish status

Classified as Endangered (EN - A1ace, B1 + 2abce) on the IUCN Red List 2003 (1) and as Vulnerable on Tasmania’s Threatened Species Protection Act 1995 (3).

IUCN Red List species status – Endangered

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Giant freshwater crayfish threats

The major threat to this species has been over-fishing, since these crayfish are a popular food dish, but this has not been sustainable due to extremely slow maturation and infrequent breeding (5). Habitat loss is also a threat, as a result of increasing agricultural expansion, forestry operations and changes in water quality (3). In-stream barriers have reduced the dispersal potential of the crayfish and erosion following agricultural expansion has caused silty water, which is less favourable for the giant freshwater crayfish (4).

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Giant freshwater crayfish conservation

The decline of giant freshwater crayfish numbers following intense resulted in a fishing ban in January 1998, although an ongoing commitment is needed in order for the crayfish to recover from its endangered status. Population surveys and behavioural research are being undertaken in order to be able to provide better habitat protection and improved management of riverbank vegetation (3).

View information on this species at the UNEP World Conservation Monitoring Centre.
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Find out more

For more information see:

Animal Diversity Web (September 2004):
http://animaldiversity.ummz.umich.edu/site/accounts/information/Astacopsis_gouldi.html

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Crustacea
Diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, slaters, woodlice and barnacles.
Omnivore
An organism that feeds on both plants and animals.
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References

  1. IUCN Red List (September, 2004)
    http://www.redlist.org
  2. Animal Diversity Web (September, 2004)
    http://animaldiversity.ummz.umich.edu/site/accounts/information/Astacopsis_gouldi.html
  3. Australian Government – Department of the Environment and Heritage (September, 2004)
    http://www.deh.gov.au/biodiversity/threatened/information/factsheets/lobster.html
  4. Inland Fisheries Service (September, 2004)
    http://www.ifs.tas.gov.au/fact_sheets/a_gouldi.html
  5. The Giant Tasmanian Freshwater Lobster (September, 2004)
    http://www.lobsters.tascom.net/page4.htm
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Image credit

Giant freshwater crayfish  
Giant freshwater crayfish

© Neil Armstrong

Neil Armstrong
silverbudgie@optusnet.com.au

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