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MCSS
have been running trials with a spot pattern
recognition programme to compare digital images of whale
sharks accumulated over the years. The programme was
originally developed to help identify Ragged Tooth
sand-tiger sharks is named IRIS for Interactive Raggie
Identification System.
Three
land mark points calibrate each image and then the user
defines the centre of up to 30 spots on each image to
create a ‘fingerprint’ of the markings. The programme
then compares these fingerprint files to the fingerprints
stored in the database and shows the user the best 10 matches.
The user
can then compare each of the images visually to confirm if
the unknown shark is the same as the suggested sharks from
the database. There is also a ‘spot cloud’ comparison
facility which shows how the spots from the unknown shark
pair up to those from the identified shark.
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The
Iris programme comparing
whale shark images from Seychelles. Image MCSS |
Currently,
photo ID of whale sharks is generally done on the spot
pattern on the area behind
the gill slit and on dorsal fin. To start this
project off we took a series of digital photos of a life
sized painting of a whale shark gill slit and dorsal fin
at increasing angles away from the perpendicular. This
gave us a good idea of the range of tolerance that the
programme had to correctly identify images of the same
shark.
Once
the system’s limitations were known a selection of this
year’s images were fingerprinted and then compared to
images submitted by the Seychelles Whale Shark Monitoring
Network last year and on the very first run through we got
a match! An untagged shark photographed by Big
Blue Divers on 1 December 2005 was matched to a shark
photographed on the 2nd September 2006 in the south of
Mahe by the MCSS monitoring team.
Photo
ID does not give the immediate recognition or certainty of
identification that tagging with marker tags does, but it
will certainly provide an additional and valuable tool for
identifying untagged sharks. The IRIS software will help
us match the digital images of the whale sharks we get
sent in as well as those generated by the monitoring team.
At the end of each season the ID photos will still be
submitted to the EcOcean and the PADI Project Aware
databases to see if the sharks are being sighted in other
regions as well.
Currently
the IRIS programme is also being used for whale shark
photo identification in Mozambique and Australia and it is
hoped that these areas will collaborate on sharing IRIS
fingerprints to see if there is any movement of whale
sharks across the region.
If
you have whale shark photos please do send them through to
us with details of where and when they were taken;
individual images of less than 500K can be sent by e-mail,
larger images or multiple images we would prefer came on a
CD as the local mail server does not like big attachments!
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