Life - First recording of deep-water fish chat

Something sounds fishy. For the first time, grunts and quacks possibly made by fish living on the sea floor have been recorded.

These fish may lack a conversation partner, though, if underwater noise pollution covers their quiet calls.

More than 50 years ago, scientists dissecting deep-water fish noticed that they had sound-producing muscles like those in noisy, shallow-water fish. However, recording sound in deep water is difficult, so it was unknown if fish actually used those muscles to create calls.

Listening to fish

Rodney Rountree of the University of Massachusetts in Amherst and his colleagues have now placed an underwater microphone on the Atlantic ocean floor specifically to listen to deep-water fish calls.

The researchers attached the microphone to an MP3 player and mounted the device in a plastic case. Fisheries workers in Massachusetts placed the recorder inside a crab trap, which was lowered onto the North American continental shelf, 682 metres below sea level.

The 24-hour recording captured at least 12 unknown grunting, drumming and duck-like sounds with frequencies below 1.2 kilohertz (listen to them here) – within the range for fish calls or potentially low-frequency whale calls.

Conjugal conversations

Like their shallow-water cousins, deep-water fish may call each other during their mating season. These conjugal conversations may be especially important to deep-water fish because there is little light down there to find potential mates by.

If these fish communicate through sound, background noise from passing ships could drown out their conversations. But before the full effect of noise pollution is known, the aquatic chatterboxes must first be identified and their banter translated. "This is a whole area of the ecology of these fishes that we know almost nothing about," says Rountree.

"Some of the sounds are almost for sure from fish because of their characteristics," says zoologist Michael Fine of Virginia Commonwealth University in Richmond, who was not involved in the study. All deep-water fish with sound-producing muscles probably vocalise, though, and any of them could be responsible for the calls, he adds. "It's so tough making a living in the deep sea that [fish] aren't going to have a frivolous organ that does nothing."

Reference: The Effects of Noise on Aquatic Life, published by Springer

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