[MARMAM] Paracas dolphins skin disease and fishing strategies

Stefan Austermühle mundoazul at terra.com.pe
Tue Oct 3 05:14:54 PDT 2006


Dear Julio and Marmamers
 
I just returned from Mundo Azuls first month of field work
photo-identifying bottlenose dolphins in the area between Perus Capital
Lima and the Island Asia (100 km of coastline) and the area between
Paracas and Tambo de Mora (40 km). According to our preliminary analysis
of the several thousands of pictures taken, in the first area we managed
to determine several distinct populations with a total of at least 180
dolphins. In Paracas/Pisco we managed to photo identify at least 85
dolphins with some aditional ones in the area between Pisco and Tambo de
Mora. I would like to confirm Julios observation. Of the 85 dolphins we
identified in the area Pisco/Paracas, which is heavily afected by
contamination, at least 16 of the 85 dolphins we encountered showed this
skin condition. Diving studies of Mundo Azul in 2004 and 2006 collecting
a total of 400 bottom samples and invertebrate samples have shown that a
great area  (approximately 15 square kilometers within the bay) are near
biologically dead or bilogically dead, with the bottom being covered by
a thick layer of gelee like organic matter (information concerning this
contamination, satelite images and research results can be obtained on
our english web site within the part on marine contamination -
www.mundoazul.org <http://www.mundoazul.org/>  - click on the british
flag in the upper right corner in order to enter in the engish version).
This year we also could confirm a heavy contamination with petroleum
accumulated in the seafloor south of Pisco.
 
In the other populations that we identified so far we could not find one
single specimen showing a similar skin condition. With exemption of a
small group near the capital in an area where a main sewage pipe enters
contaminating the sea with the sewage of a few milion people. We do not
yet have a lot a pictures from this group as sea conditions during our
stay in the are have been very tough but the few pictures we were able
to take so far showed at least one dolphin with a similar skin contidion
like the dolphins in Paracas. From this we can conclude that there
definitely can be assumed a connection between the contamination and the
skin disease, as Julio points out. As our field investigaion in the area
goes on I am sure that I can provide more input for the list on this
topic. I therefore would be also very interested to get more information
on this type of skin disease and would like to ask listmembers to also
forward their information to our emal: mundoazul at terra.com.pe
 
I would like also to raise another interesting topic concerning the
Paracas population and ask list members for literature and comments on
similar behavior in other populations. The bay of Paracas is very
shallow. We could observe dolphins to perform the following feeding
behavior in water depths of 1.5 to 5 meters. A single dolphin or groups
of up to three dolphins swam in tight circles with the snout aparantly
in the sediment and the fluke out of the water (sometimes vertically)
steering up a lot of sediment. We thought of several possible
explanations: they might have fished bottom dwelling fish or have
steered up sediment in order to confuse fish and catch them in the murky
water caused by this behavior - it could also be that the steered up
sediment and organic material attracts fish which then can be caught by
the dolphins. The later seems a probable hypothesis as we could also
observe a similar behavior related to fishing boats. Artisan fishing
boats entering the harbor of Paracas are used to pump out their bilges
and throw the fishblood and remains into the water when cleaning their
wooden boats. This organic material seems to attract fish which then is
consumed by the dolphins. We observed that whenever a fishing boat
enters in the port a huge number of dolphins (up to ten) follows the
boat and then fishes around the anchored boat witin the water that is
contaminated with the organic waste, while fishermen continue to throw
over board bloodwaer and clean their boats. I would be very interested
to learn if similar behaivors have been observed in other places. I am
sure that Julio can confirm this behavior and maybe would be interested
to also receive information from listmembers about similar fishing
behaviors in other places.
 
All the best
 
Stefan Austermühle
Mundo Azul
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