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Dear List,

Living in La Parguera, PR and spending my time mostly
at the Isla Magueyes marine station I have visited the
bay (Bahia Fosforescente) numerous times.  The last
time during November '04, I noticed a sound at night
at a high frequency which I think could be similar to
the one this gentleman writes about.  However, due to
the boat traffic that may pass the area (especially
the large glass bottom boat which arrived shortly
thereafter) and the occasional presence of marine
mammals...I've seen a manatee in the bay during the
day and dolphins in front of the bay near the deeper
waters adjacent and in front of the bay...I believe it
is likely one of these two situations, as I am unaware
of fishes in the area that produce sounds at such
persistent high frequencies.  The bay is mostly
mangrove forest and soft bottom sediments, while
surrounding habitats are some shallow seagrass, soft
bottom and reef habitat located in front of and
adjacent to the bay.  But these are pretty far away
from the central areas of the bay where
biolumenescence is usually strongest in deepest depth,
and where many people congregate to swim.  One
fisherman has also told me that shrimp snapping on the
bottom can also be heard in the area.

As sound travels further in water it is possible that
as a boat was passing near the area with high
frequency propeller sound or a marine mammal producing
sound from further away, it eventually passed the
gentleman in the water creating an interpretable
doppler effect.

Hope this might offer some perspective or start
another argrument.

TONY MARSHAK
M.S. Student
Isla Magueyes Marine Station
Department of Marine Sciences
University of Puerto Rico - Recinto de Mayaguez

http://cima.uprm.edu





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