Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences
RESEARCH ARTICLE (Open Access)

Long-term membership of whale sharks (Rhincodon typus) in coastal aggregations in Seychelles and Djibouti

David Rowat A F , Katie Brooks A B , Abi March A , Ciara McCarten A , Daniel Jouannet C D , Luke Riley A , Gareth Jeffreys A E , Morgan Perri D , Michel Vely C D and Bruno Pardigon C

A Marine Conservation Society, Seychelles, PO Box 1299, Victoria, Seychelles.

B Environment Department, University of York, Heslington, York, YO10 5DD, UK.

C Marine Conservation Society, Djibouti, PO Box 4476, Djibouti.

D Megaptera, 23 Rue Alexandre Dumas, 75011, Paris, France.

E Aberystwyth University, Penglais, Aberystwyth, SY23 3DA, UK.

F Corresponding author. Email: david@mcss.sc

Marine and Freshwater Research 62(6) 621-627 http://dx.doi.org/10.1071/MF10135
Submitted: 15 June 2010  Accepted: 28 February 2011   Published: 24 June 2011

Abstract

In coastal waters of several locations globally, whale sharks (Rhincodon typus) form seasonal aggregations, most of which largely comprise juvenile males of 4–8 m length. Evaluation of the period that individuals stay within these size- and age-specific groupings will clarify our understanding of the transition between life-stages in this species and how this might affect their long-term conservation. Long-term photo-identification studies in Seychelles and Djibouti provided data to evaluate this. The Seychelles aggregation had 443 individuals averaging 5.8 m identified between 2001 and 2009; however, the Djibouti aggregation comprised smaller individuals of 3.7 m mean length with 297 individuals identified between 2003 and 2010. In Seychelles, 27% of individuals identified in 2001 were seen again in 2009, while in Djibouti none of the whale sharks identified in 2003 were seen in 2010, although 13% from 2004 were. This suggests that membership periods in the Djibouti aggregation are shorter than in the other juvenile aggregations, such as in Seychelles. Continued photo-identification monitoring of other Indian Ocean aggregations might in time show the next location of these young sharks’ life-cycle and thereby allow development of informed national and regional management plans.

Additional keywords: demographic composition, photo identification.


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