Abstract

Otolith shape analysis was used for discriminating stocks of Epinephelus morio (red grouper) from the Campeche Bank. Since red grouper is the most commercially exploited specie in Yucatan, to identify different stocks becomes a major issue for fishery management. From a total of 420 red groupers sampled between 1996 and 1999 by commercial and artisanal fleets, 373 individuals were analyzed. Both otoliths (sagittae) were removed through the gill arch, alcohol cleaned and stored dry in small paper bags. Each left otolith was measured to obtained otolith length (OL; 0.001cm), otolith width (OWi; 0.001cm) and both otoliths were weighed to obtained the weighted average (OW; 0.0001 g). Each left otolith was consistently oriented at a 45° position (sulcus side down, rostrum upwards) and digitally photographed using a stereomicroscope at 0.4× and 0.5× equipped with a videocamera. Otolith shape was determined through Age & Shape software (Infaimon S.L. â) using wavelets descriptors (WLT), and then compared by principal components (PCA) and Multi-dimensional Scaling analysis (MDS) (Primer 6.1.12, PRIMER Ltd.). Red grouper standard length ranged from 33.0 cm to 83.0 cm and gutted weight 650.0 g to 13200.0 g. Otoliths meristics varied from 0.6679 - 1.1340 cm OWi, 1.2875 – 1.9992 cm OL and 0.0823 – 0.9516 g OW. Through the shape analysis, 512 random measure-ments for each of 10 WLT scales were calculated. The hierarchical cluster analysis (WPGMA) showed four distinct groups (at 0.005) using only WLT5, WLT6 and WL7 (established by PCA) and six different groups using all the WLT (at 0.05). Apparently, no differences on the otolith shape could be identified.

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