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Scientists
lend an ear to fish-talk
Baby fish tune into
sounds while still in the egg
By Karen Graydon
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Baby fish still in the egg can hear the
conversations of their parents, according to research being
carried out by an international team of scientists from the
University of York, the Australian Institute of Marine Science
and the University of Kentucky.
The project builds on associated work
by AIMS at Lizard Island showing fish speak to one another in
a series of grunts, squeaks and whistles, inaudible to the
human ear.
Embryonic fish
AIMS fish
ecologist Dr Mark Meekan has been supervising PhD student
Stephen Simpson of the University of York in the UK, while
he researches noises made by fish. Recordings of
underwater reef noises were made, then played back in fish
traps.
Dr Meekan
said greater numbers of baby fish were collected in the
fish traps broadcasting the recordings of reef noises than
in the traps without the reef noise, showing that fish
were drawn to particular reef sounds.
Species
from fifteen families of common reef fishes (including
damselfish, soldier fish and cardinal fishes) were
attracted to the recordings, some of which were also
placed on artificial reefs near Lizard Island.
"We re
not certain yet whether the fish are drawn to the whole
spectrum of sounds from the reef, or whether they are
honing in on one particular sound perhaps the fish-talk of
an adult of the same species," he said.
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A submariners tale
| I loved Mark Meekan's description of the sounds fish make in the ocean on this mornings' "Fish Ears" on ABC Radio National.
It took me back to my periods at sea when I served in submarines as a Sonar Operator (21 years), in oceans all over the world. During the quiet periods in the "graveyard watch" when the submarine would be deep and quiet, I would listen to the biological sounds of the ocean, and came to recognise various species of fish by their distinctive "chatter", such as snapping shrimp, carpenter fish (easy to recognise!), and in particular the larger marine mammals.
I remember once on a patrol in the North Sea, and we were up around the Færoe's Gap inside the arctic circle. For about my entire watch of four hours listening on the hydrophones I was serenaded by whales calling one another across the north pole. The long mournful sounds were obviously coming from a long way away, as the doppler effect was quite marked.
Occasionally dolphins or porpoises would come right up close to the hydrophones, and let loose with a barrage of whistles, pops and crackles, forcing one to tear off the headphones because of the sudden
increase in
dBs!
I'm sure that they used to do it deliberately! I particularly liked their "creaking door" sounds.
During the Evening and Dawn Chorus, which would last for about two hours each time, it was a cacophony of noise, and used to drive the sonar operators mad.
Thanks for the article, and more so the wonderful memories it
invoked.
Regards, Dave Bryant,
 Kockums Pacific Technology Pty. Limited.
Sound files
Snapping shrimp wav file
320K ~15 secs
Nocturnal zooplanktoniverous fish
wav file 204K ~10 secs
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Fish eggs in nest
The fish’s response to the reef noise explains how baby
fish that are swept off the reef out to open seas manage to
find their way back again.
Dr Meekan said many things on the reef eat newly hatched
fish. "So once they are hatched, the baby fish are swept
out to the ocean where they are less likely to be eaten, until
they reach a certain size, before they work their way back to
the reef. We believe reef noise is what guides them
back," he said.
Sound travels so efficiently underwater that some noises
made by adult fish on the reef can be heard 15 km away.
At dusk and dawn, the chorus of fish noises reached a
crescendo, equivalent to the roar of thousands of individual
voices at a football stadium.
Fish eggs
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Larval fish
in plankton
Adult coral reef
fishes
Equipment at Dr.
Hong Yan's
laboratories at the University of Kentucky
used
in the experiments
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In the latest research in collaboration with Dr Hong
Yan at the University of Kentucky,
Stephen Simpson monitored the heartbeats of clownfish embryos
as they were played noises of different frequencies. By varying the volume
they were able to see how their sensitivity increased during
development.
The sounds they responded to were in the same range
as those produced by reef fishes and invertebrates. This suggests that embryos
have experienced their reef before hatching and heading out to sea.
The next question this posed
was whether or not the fish embryos were "imprinting" their parents
fish-talk, and were responding to it when they hatched.
Dr Meekan said the research was
giving marine biologists greater understanding of the ecology of fish and how
to manage this resource.
"Human beings add a lot of
noise to the ocean by the use of boats. The question we have to ask is whether
or not this is making the already noisy oceans even noisier, and maybe
affecting how fish hear the noises they need for survival."
Acknowledgements
Stephen D. Simpson - University of York, UK
Matthew L. Wittenrich - Freelance, USA
Hong Y. Yan - University of Kentucky, USA
Mark G. Meekan - AIMS, Australia
Photographs by
Stephen D. Simpson - University of York, UK
For more information
contact
Stephen Simpson, University
of York
e-mail: simpsonstephen@hotmail.com
Dr. Mark Meekan, Australian
Institute of Marine Science
e-mail: m.meekan@aims.gov.au
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