It may sound like codswallop but scientists have discovered that the midshipman fish hums to attract a mate.

Science journal Current Biology has published the findings of a US research team who have been investigating the foghorn-like hum of the midshipman fish, which they have discovered is actually a courtship call controlled by the hormone melatonin.

As reported by BBC News, houseboat residents in California in the 1980s thought that the low hum they heard at night might be coming from sewage pumps, military experiments or even extraterrestrials. But when researchers took the fish into their labs, they found that the ‘singing’ was controlled by melatonin – which humans use to help with sleep and overcoming jet lag. Looking closely at how the melatonin acts on various receptors in the fish’s brain could help explain why it has such a powerful effect on circadian rhythms, reproduction and also birdsong.

The aptly named Professor Andrew Bass, who led the research, became fascinated by the midshipman fish after reading a paper written in 1924 by an academic called Charles Greene, which described how the male fish would hum at night. Prof Bass told BBC News: “Greene referred...