Tasmania’s Giant freshwater lobster – the world’s largest freshwater invertebrate

No. 48

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The Tasmanian rivers and creeks draining into Bass Strait are home to the planet’s largest non-marine invertebrate. Known to the scientific community as Astacopsis gouldi, the giant freshwater lobster is also sometimes called a crayfish, in keeping with its stature and suitability for the pot (although it is now illegal to harvest this threatened species from the wild).

Tasmania and south-eastern Australia represent a global hot-spot for non-marine crayfish, which all belong to an ancient lineage. Most live in burrows in damp ground, but the giant freshwater lobster and its relatives (the more modestly proportioned southern A. tricornis and the positively Lilliputian eastern A. franklinii) require flowing water – though they will travel overland if they need to, and occasionally inhabit dams.

The giant freshwater lobster lives life in the slow lane. Adults may live for 40 years, by which time they may be 80 cm long and weigh in at more than 5 kg. Females don’t start breeding until they are about 14 years old, and then only do so every other year because it takes them that long to brood their eggs and youngsters. They eke out a living on a meagre diet of dead leaves and rotting wood, but will also eat living invertebrates, and dead fish and mammals that happen to drift their way.

Because of past overfishing, large individuals are rare today – albeit a little less so than before the species received official protection in 1998. Continued threats include poaching, loss of vegetation, and changes to water quality and flow-rates due to land management practices within the catchment.

The lobster’s specific name – given in 1845 – honours the convict artist, William Buelow Gould, whose 1832 Sketchbook of Fishes (now in Hobart’s Allport Library) includes the first-known representation of an Astacopsis and inspired Richard Flanagan’s 2001 novel, Gould’s Book of Fish.

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