The prawn on the other side of the line

23 November 2026

Part 13 of 18 · A history of the giant freshwater prawn

Every year between March and May, young giant freshwater prawns head up the Daly River in the Northern Territory, en masse, over four to six weeks. In one season, a researcher counting them estimated somewhere between 14 and 18 million; one estimate put their weight at about a tonne.[1][2] They hatched upriver, drifted down to the estuary as larvae, which must reach salt water within five to seven days (Part 1), and are now walking and swimming home.[1]

They are not quite the prawns the rest of this series has been about.

In 2004, geneticists at the Queensland University of Technology mapped the species across its range and found it split in two: a western form, the one farmed across Asia, and an eastern form, Australia’s.[3] The boundary between them follows a line drawn through the islands of Southeast Asia in the 1860s.[4]

Alfred Russel Wallace drew the first version in 1859, after years of collecting specimens in the Malay Archipelago, to mark where Asia’s wildlife gives way to Australia’s: between Bali and Lombok, and between Borneo and Sulawesi. In 1868, Thomas Henry Huxley redrew its northern end around Palawan, in the Philippines, and named the line in Wallace’s honour.[5] The prawns follow Huxley’s version.[4] So Australia’s giant prawn lives on the far side of the Huxley line.

On this side of the Huxley line, the prawn lives in the rivers of the Northern Territory, Queensland and Western Australia, from the Fitzroy River basin in the Kimberley to the Jeannie River on Cape York; the first scientific record came from the Katherine River.[6] On the Daly, it is the favourite bait for barramundi.[7]

Australian scientists have studied it closely. Besides the genetics in Brisbane, a hatchery study at James Cook University in Townsville raised larval survival from 30 to 71 per cent by adding microalgae to the tanks,[8] and found adult females still moulting in water as cold as 12 °C.[9] At Charles Darwin University, Peter Novak followed the prawn’s life along 400 kilometres of the Daly.[1] Much of that science went to work abroad. QUT’s geneticists helped a Vietnamese research institute breed a strain that grows 25 per cent faster, and took the prawn to Fiji and Vanuatu.[10]

At home, farming never caught on. Hawaii’s success inspired early attempts in Australia (Part 2),[11] but none of them lasted, undone by low hatchery survival, cannibalism, disease, and too little expertise and infrastructure to produce young prawns reliably.[9]

The next attempt began in 2017, in the Kimberley. This time, Aboriginal corporations led it.

Sources

1. Novak, P. A., The life history and ecology of Macrobrachium spinipes in northern Australia. PhD thesis, Charles Darwin University. About 18 million juveniles in one season; larvae must reach salt water within five to seven days; upstream migration over four to six weeks, March to May; 400 km of the Daly River. cdu.edu.au
2. Charles Darwin University news (2014), Wet season flows crucial to cherabin survival. About 14 million juveniles, about 1,000 kg. cdu.edu.au
3. de Bruyn, M., Wilson, J. A., Mather, P. B. (2004), Huxley’s Line and the phylogeography of the giant freshwater prawn. Molecular Phylogenetics and Evolution 30: 251–257.
4. van Tol, J. (2009), Phylogeny and biogeography of the Platystictidae (Odonata), Leiden University. The boundary between the prawn’s two forms proved to be Huxley’s (1868) line, which differs from Wallace’s (1863) only in the position of the Philippines. universiteitleiden.nl
5. Esselstyn, J. A., Oliveros, C. H., Moyle, R. G., et al. (2010), Integrating phylogenetic and taxonomic evidence illuminates complex biogeographic patterns along Huxley’s modification of Wallace’s Line. Journal of Biogeography 37: 2054–2066. Huxley (1868) both named and modified Wallace’s Line.
6. Australian Faunal Directory, Giant river prawn; Short, J. W. (2004), as summarised in Lober (2015). Range and first record. biodiversity.org.au
7. Cosmos, Shrinking rivers threaten Australia’s super shrimps. cosmosmagazine.com
8. Lober, M., Zeng, C. (2009), Effect of microalgae concentration on larval survival, development and growth of an Australian strain of giant freshwater prawn. Aquaculture 289: 95–100.
9. Lober, M. (2015), Investigation of the aquaculture potential of an Australian freshwater prawn. MSc thesis, James Cook University. Females moulting at 12 °C; past commercial attempts and why they failed. doi.org
10. The Fish Site (2011), Fast-growing prawn breakthrough helps farmers; Asian Scientist (2011). QUT and Vietnam’s Research Institute for Aquaculture No. 2; Fiji; Vanuatu. thefishsite.com
11. New, M. B. (1987), Freshwater prawns: status of global aquaculture. FAO. Early attempts “in many other places, including Australia”. fao.org

Part 13 of 18 · A history of the giant freshwater prawn · Previous: Part 12, The prawn’s night shift: turn off the lights and the party starts · Next: Part 14, Jarramba: the Kimberley’s giant prawn · SHRMP.bio’s strategy behind it: shrmp.bio/strategy.html