Fish can apparently have a talent for singing. Scientists have unsolved the mystery behind California's "singing fish" in a new study.

The midshipman fish apparently emits a bizarre, low hum. Male fish often do this as a courtship call, according to scientists from Yale University and Cornell University.

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During their investigations, the team identified the hormone that controls this bizarre ability in the fish, which is also the same hormone that helps human to sleep at night called melatonin.

Scientists examined how melatonin interacts with the fish's brain receptors, revealing a powerful "chemical clock" that also coincides with the fish's sleep-wake cycles and reproduction, including this mating call.

According to the lead author of the study, Andrew Bass of Cornell University, females fishes of this species are also sonic, but when males become territorial, they build nests then hum to attract females into those nests.

Scientists have placed a group of midshipman fish in constant exposure to light to observe if their humming is controlled by a circadian rhythm or internal clock. The findings revealed that light suppressed their humming.

Bass and his team then gave the fish a melatonin substitute, and the fish continued to hum during different times of day randomly, without any rhythm. This confirmed that melatonin is a trigger for the midshipman's nocturnal songs.

This new study suggests that melatonin plays a crucial role in not just the midshipman fish but also among other animals. This can also reveal important evolutionary clues about fish since the presence of a body clock also suggests complex brain development.

According to the co-author of the study, Ni Feng of Yale University, melatonin in humans allows us to fall asleep easier and get over jetlag faster. In nocturnal fish, this supplement works by waking them up to make way for mating calls.

The team also believes that studying nocturnal singing fish can become a useful model for studying hormones and reproductive-based vocal behaviors that have been observed in many vertebrates.

This new study has been published in the journal Current Biology.