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Fish breaking new gaia grounds

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  • Mike Doran
    Fish farting may not just be hot air By Celeste Biever Biologists have linked a mysterious, underwater farting sound to bubbles coming out of a herring s anus.
    Message 1 of 1 , Nov 6, 2003
      Fish farting may not just be hot air

      By Celeste Biever

      Biologists have linked a mysterious, underwater farting sound to
      bubbles coming out of a herring's anus. No fish had been known to
      emit sound from its anus nor to be capable of producing such a high-
      pitched noise.

      "It sounds just like a high-pitched raspberry," says Ben Wilson of
      the University of British Columbia in Vancouver, Canada (Listen
      here , .wav file). Wilson and his colleagues cannot be sure why
      herring make this sound, but initial research suggests that it might
      explain the puzzle of how shoals keep together after dark.

      "Surprising and interesting" is how aquatic acoustic specialist
      Dennis Higgs, of the University of Windsor in Ontario, describes the
      discovery. It is the first case of a fish potentially using high
      frequency for communication, he believes.

      Arthur Popper, an aquatic bio-acoustic specialist at the University
      of Maryland, US, is also intrigued. "I'd not have thought of it, but
      fish do very strange and diverse things," he says

      Grunts and buzzes

      Fish are known to call out to potential mates with low "grunts and
      buzzes", produced by wobbling a balloon of air called the swim
      bladder located in the abdomen. The swim bladder inflates and
      deflates to adjust the fish's buoyancy.

      The biologists initially assumed that the swim bladder was also
      producing the high-pitched sound they had detected. But then they
      noticed that a stream of bubbles expelled from the fish's anus
      corresponded exactly with the timing of the noise. So a more likely
      cause was air escaping from the swim bladder through the anus.

      It was at this point that the team named the noise Fast Repetitive
      Tick (FRT). But Wilson points that, unlike a human fart, the sounds
      are probably not caused by digestive gases because the number of
      sounds does not change when the fish are fed.

      The researchers also tested whether the fish were farting from fear,
      perhaps to sound an alarm. But when they exposed fish to a shark
      scent, there was again no change in the number of FRTs.

      Night waves

      Finally, three observations persuaded the researchers that the FRT is
      most likely produced for communication. Firstly, when more herring
      are in a tank, the researchers record more FRTs per fish.

      Secondly, the herring are only noisy after dark, indicating that the
      sounds might allow the fish to locate one another when they cannot be
      seen. Thirdly, the biologists know that herrings can hear sounds of
      this frequency, while most fish cannot. This would allow them to
      communicate by FRT without alerting predators to their presence.

      Wilson emphasises that at present this idea is just a theory. But the
      discovery is still useful, he says. Herring might be tracked by their
      FRTs, in the same way that whales and dolphins are monitored by their
      high-pitched squeals. Fishermen might even exploit this to locate

      There may even be a conservation issue. Some experts believe human-
      generated sounds can damage underwater mammals. Now it seems
      underwater noise might disrupt fish too.

      Journal reference: Biology Letters (DOI: 10.1098/rsbl.2003.0107)


      Air bubbles much like ship props issue and would bring proteins to
      surface and impact conductivity and provide a mechanism to cause bio
      cirrus particle connection.
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