Deep sea fish communicate through sound


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Fish biologists from Massachusetts have released the first study of deep sea fish sounds in over 50 years.

The historical study hypothesised that deep sea fish probably produced a wide variety of sounds due to the fact that many of them have the muscles needed to produce them.

Up until now however, very few studies have actually taken place to find out whether the fish really do make noises.

Together with commercial fishermen, the scientists developed a simple deep-water hydrophone - basically an mp3 player in a plastic case (shown above being deployed).

With the device, they recorded 24 hours of deep-water sounds from the seafloor about  862m below the surface of Welkers Canyon; south of New England's Georges Bank.

From the recording the scientists reported the sounds of whales, and dolphins but also 12 other unique and unidentifiable noises.

Prior to this study it was believed that whilst most fish make incidental noises due to swimming and eating, deep sea fish may well rely on noises to communicate in the perpetual darkess.

Deepwater fish are notoriously difficult to keep in captivity and low cost technology didn’t exist to record the sounds to establish whether they do make noise.

Lead author Rodney Rountree, a marine ecologist at the University of Massachusetts, Amherst said: "…just because they have the anatomy to make noises, doesn't mean they necessarily do it. In terms of communicative sounds, we don't know what proportion of the fish do it."

The noises recorded by the hydrophone includes grunts, drumming and quacking and chirping. These could be from whales, but they could also have come from deep-sea fish.

"Most fish only hear low frequencies and only produce low-frequency sounds," Rountree said. "The sounds we recorded were in the range that fish typically use."

Whilst the team don’t yet know the meaning of the grunts and calls, the worry is that these sounds were barely above background level and as the noises made by man increases, it may mask the noises fish make to each other.

Rountree and his team are now trying to develop a listening system that incorporates video, in hopes of identifying the creatures that made the enigmatic noises. However, the work has been difficult. "When we try to incorporate video, the price tag goes way up, because video requires light, and powering the light becomes a problem," Rountree said. "Right now we are still on the drawing board with trying to come up with a good way to do this."

The study appears in the new book, "Effects of Noise on Aquatic Life" (Springer, 2012).

Samples of the sounds can be downloaded on the Fish Ecology website.

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