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Auteur (up) Mahé, K.; Evano, H.; Mille, T.; Muths, D.; Bourjea, J. url  doi
openurl 
  Titre Otolith shape as a valuable tool to evaluate the stock structure of swordfish Xiphias gladius in the Indian Ocean Type Article scientifique
  Année 2016 Publication Revue Abrégée African Journal of Marine Science  
  Volume 38 Numéro 4 Pages 457-464  
  Mots-Clés Connectivity; Fourier descriptors; morphometric markers; sagittal otoliths; stock discrimination  
  Résumé Swordfish Xiphias gladius is an oceanic-pelagic species. Its population structure in the Western Indian Ocean was studied from the shape of the sagittal otoliths of 391 individuals collected from 2009 to 2014. Normalised elliptical Fourier descriptors (EFDs) were extracted automatically using TNPC software. Principal components analysis (PCA) conducted on EFDs showed no significant effect of side (i.e. left or right otolith). Consequently, all 391 sagittal otoliths were used to identify stocks among six geographical areas: Reunion Island, Mozambique Channel, Rodrigues, South Africa, Madagascar South and Sri Lanka. To investigate the effects of sex, sampling year, sampling season, lower jaw fork length or geographical area on variations in otolith shape, redundancy analyses (RDAs) with permutation tests were conducted. The first four were non-significant (respectively, p = 0.124, p = 0.721, p = 0.197, p = 0.463), but geographical area appeared to discriminate groups significantly (p < 0.05). Furthermore, linear discriminant analysis (LDA) was performed and overall jackknife classification success reached 30%. Finally, a cluster analysis was conducted using Ward’s hierarchical algorithm, which discriminated three different groups. However, each group consisted of individual samples from all geographical areas. In conclusion, our results were unable to identify a clear geographical separation of swordfish at the Indian Ocean scale, corroborating recent genetic studies in this region.  
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  ISSN 1814-232x ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1708  
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