February 1st to 5th 2016
Olhão, Portugal
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Photo-identification and bioacoustics analysis to investigate the growth of sperm whale (Physeter macrocephalus) and its movements in the Mediterranean Sea

Scientific Exhibition
Biodiversity Effects
Thursday, February 4, 2016 -
17:30 to 19:30

Briola, A. 1 Carpinelli, E. 2 Airoldi, S. 3 David, L. 4 Di Meglio, N. 5 Pavan, G. 6

1CIBRA, University of Pavia, Italy
21. CIBRA 2.Tethys 3. CIRCE
3Tethys Research Institute, Viale G. B. Gadio 2, 20121 Milan, Italy

This work combines photo-identification and bioacoustics to study the body growth and the movements sperm whales in the Mediterranean Sea. The Mediterranean sperm whale is a sub-population considered endangered according to ACCOBAMS and IUCN. Hence it is necessary to study sperm whales, their ecology, their population structure, distribution and movements to implement appropriate conservation strategies. Four individuals size estimated, photo-identified and recorded in the Ligurian Sea (Italy) by CIBRA in 1994-1997 have been searched in photo-id catalogues available from other areas of the Mediterranean Sea. Two of the individuals have been recaptured photographically in the Western Ligurian Sea by Tethys and one of them also in the Gulf of Lion (France) by EcoOcèan, in different years (31 resightings in years 1994-2014). CIBRA and Tethys also performed acoustic recording of the photo-identified whales by means of a towed array of hydrophones. It was possible to retrieve the original recordings and to accurately measure the Inter Pulse Interval of the recorded sperm whales’ clicks by using cepstral techniques. The IPI measure allows to estimate the size of the recorded whales. The IPI analysis of the two whales photographically recaptured reveals that have grown up respectively by 68 cm in 16 years (4.25 cm/year), and 79 cm in 20 years (3.95 cm/year) and give the size estimation of the other two no photographically recaptured. The growth rate fits to the curve of asymptotic limit of the maximum size reached by the species. The adults measured are smaller then the Atlantic’s, and thanks to comparison with stranded animals it is possible to estimate the age. This work demonstrates the importance of the multidisciplinary approach and of the data sharing between different research institutes. It is also demonstrated that the combination of photo-identification and bioacoustics allows to obtain important information about the ecology of sperm whales.
Sperm whale, Photo-ID, marine bioacoustics, IPI, body-growth

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