The use of different otolith-shape analyses for stock discrimination of Yellowtail Snapper Ocyurus chrysurus, (Bloch, 1791) in the coastal waters of northeastern Brazil

In this study, the otolith morphology of yellowtail snapper (Ocyurus chrysurus) was used for stock identification based on different shape analyses viz. morphometric parameters with shape indices, Elliptical Fourier descriptors (EFD), wavelet transform (WT), and landmarks. The samples were collected from Fortaleza (Ceará) and Recife (Pernambuco) in the coastal waters of Brazil to identify stocks and determine the best method for stock discrimination of O. chrysurus. The result showed no significant difference between these two regions which was supported by the Linear Discriminant Analysis (LDA). To select the best discrimination methods a correct classification through jack-knifed and Wilks’ λ test was performed. The morphometric parameters with shape indices showed a correct classification of 25% and the landmark method’s correct classification was 33.1%. These two methods had a lower correct classification than the otolith contouring methods (EFD = 42.3% and WT = 43.5%). Also, the Wilks’ λ test showed lower power discrimination for morphometric with shape indices and landmark method (λ= 0.904 and λ= 0.808, respectively), in comparison with the two contouring methods (EFD λ = 0.688 and WT λ = 0.601). These results indicate that the most suitable methods for observing small variations in O. chrysurus otoliths can be EFD and WT.