Sea robot records nighttime 'fish farts'

A team of marine biologists at the University of Florida have been using autonomous sea robots to record the sounds that fish make in order to map their distribution. They have recorded three unknown biological noises, which they believe to be fish farts.
The team from the Centre of Ocean Technology have been using autonomous gliders to study oceanography over a large area. They have attached hydrophones to the robotic vehicle and used it to detect and map fish sounds in the ocean across the West Florida Shelf. Thy were listening for typical red grouper and toadfish sounds, but detected at least three unknown biological sounds suspected to be produced by fish.
They found that the red grouper and toadfish made their regular sounds throughout the day at depths of greater than 40 metres. The suspected fish farts were detected exclusively at night and over varying depths. The team suspects that the gas is coming from a group of fish including menhaden and herring that release it from their buoyancy organ called the swim bladder. The team is continuing to map the sounds in a bid to get a better picture of species distributions and likely breeding areas.
This is not the first time that biologists have studied fish farts. A 2003 study from the University of British Columbia in Vancouver, linked a mysterious underwater farting sound to bubbles coming out of herrings' bottoms. The high-pitched raspberry sound was thought to be used by the fish to communicate in some way. Unlike human flatulence, the sounds are unlikely to be caused by digestive gases because the number of sounds did not change when fish were fed.

Thank You : Source : wired.co.uk