Do prawns hear each other?

19 November 2026

Part 11 of 18 · A history of the giant freshwater prawn

In 2021, researchers recorded giant freshwater prawns underwater while they ate. The prawns click as they chew. One prawn, recorded on its own, also made three rasping sounds that had nothing to do with food. The authors compared them with the sounds lobsters and crabs make when they fight, and left the question open.[1] It sounded like a fight, with no one to fight.

That small recording matters because of what came before it. Raised together, these prawns sort themselves into a hierarchy: a few males become bosses with long blue claws, stop growing themselves, and slow the growth of the smaller males around them (Part 5, Part 10). For forty years, researchers argued about how the bosses do it, and about what tells a male when to become one. The candidates were contact, sight, and something in the water. Nobody tested hearing. As far as I can find, what this prawn sees, smells and hears has been measured mostly in the last decade, and almost always in tanks.

Sound is not all the water carries. A 2009 thesis found that urine from blue-claw males drew females ready to mate at concentrations as low as three microlitres per litre, and stopped working once it had been cooled, frozen or heated.[2] In 2025, a study showed that fights make prawns urinate, and that the water after a fight carries raised levels of particular compounds, candidates for a chemical signal.[3] And in 2026, females turned towards a male only when his sight and his scent came from the same side.[4]

Each of these is a way a prawn could reach a neighbour it never touches. That is what the experiments of the 1980s suspected, and could not show (Part 6).

If prawns do use sound, the tank and its design become part of the conversation. In brown shrimp, a relative from the North Sea, tank noise 30 to 40 decibels above that of quiet tanks cut feeding, raised cannibalism and delayed spawning.[5] Fibreglass aquaculture tanks have been measured at about 20 decibels louder, at low frequencies, than concrete ones.[6] As far as I can find, nobody has yet measured what that noise does to the giant freshwater prawn.

What the recordings also suggest is when to listen. Most of what prawns do to each other, they do in the dark. When no one has been looking.[7]

Sources

1. Hamilton, S., Silva, J. F., Filho, F. C., Peixoto, S. (2021), Sound emission of Macrobrachium rosenbergii during feeding activity. Aquaculture Research. Feeding clicks; three rasping sounds from one prawn recorded alone, compared with the agonistic sounds of lobsters and crabs. doi.org
2. Al-Mohsen, I. (2009), Macrobrachium rosenbergii (de Man 1879): the antennal gland and the role of pheromones in mating behaviour. Thesis. Blue-claw urine attractive to receptive females from 3 µL per litre; activity lost when cooled, frozen or heated.
3. Qi, H., Shen, Q., Yu, J., Cai, M., et al. (2025), Identification of candidate pheromones and neurotransmitter regulation of agonistic behavior in Macrobrachium rosenbergii. Aquaculture Reports. Fights induce urination; fight water carries raised levels of particular compounds. doi.org
4. da Costa, F. P., Arruda, M. F., Ribeiro, K., Pessoa, D. M. A. (2026), Seeing and smelling mates. Females oriented to a male only when visual and chemical cues came from the same side.
5. Lagardère, J. P. (1982), Effects of noise on growth and reproduction of Crangon crangon in rearing tanks. Marine Biology. doi.org
6. Bart, A. N., Clark, J. A., Young, J. A., Zohar, Y. (2001), Underwater ambient noise measurements in aquaculture systems: a survey. Aquacultural Engineering. doi.org
7. dos Santos, D. B., de Almeida, L. M., de Moura, E. E. S., Arruda, M. D. F., et al. (2018), Behavior activities of Macrobrachium rosenbergii (De Man, 1879) in monosex and mixed populations, in the laboratory. Most fighting, crawling and swimming in the dark phase. doi.org

Part 11 of 18 · A history of the giant freshwater prawn · Previous: Part 10, Why the biggest males stop growing · Next: Part 12, The prawn’s night shift · SHRMP.bio’s strategy behind it: shrmp.bio/strategy.html