You can contact BNHS in this regard. Dr. Deepak Apte will be ideal to guide you on that. Also refer to the B.C. Choudhary's report of 2006, as background information.
Also you can contact Dr. Karthik Shankar in Centre for ecological sciences (CES) in Indian Institute of Science (IISc). He has done lot of work on marine turtles in Lakshadweep and Orrisa, his work is ongoing.
SPOTILA, J.R. (2004). Sea turtles. A complete guide to their biology, behavior, and conservation. The Johns Hopkins University Press. ISBN 0-8018-8007-6
you shoudl definitely contact Karthik Shankar, he has the most experience in sea turtle ecology and conservation in India. Beware that sea turtle migration studies usually involve costly satellite tags/radio tags, sonic tags. I would try a google search using sea turtle migration, tags, methods, to give you an idea of whats out there in terms of methods. You could also use a more general approach on stock connectivity using genetic methods to identify breeding stocks and how they are connected and/or intermingle in the feeding areas.
The main problem with migration studies is high cost and small sample size involved, unfortunately. Another approach we used here in Mexico to study short-term movements with very good accuracy were GPS tags that were tethered to the turtle, check out the link, maybe that could be of use to you.
Cheers and good luck.
Volker
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