AUTHOR=Ibáñez Ana L. , Guerra Ebenezer , Pacheco-Almanzar Eloísa 

TITLE=Fish Species Identification Using the Rhombic Squamation Pattern

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 7 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2020.00211

DOI=10.3389/fmars.2020.00211

ISSN=2296-7745

ABSTRACT=The shape of fish scales is to a considerable degree species-specific, making it possible to identify species using only one scale per specimen. However, the shape of the rhombic lamination pattern has not been considered to identify species. This study used geometric morphometric statistical approaches to address two specific questions: (1) whether the rhombic lamination pattern of fish scales along the longitudinal axis varies within species and sex and (2) how many fish scales of the rhombic squamation pattern should be considered to obtain an adequate identification. These questions were assessed with Mancova and cross-validated quadratic discriminant analysis (DA) using the rhombus of one, three and six scales, and six, 14 and 26 landmarks, respectively, in order to discriminate between two co-generic species, Mugil cephalus and M. curema. The proportions of the total shape variance explained by the total length and the centroid size were 2.3, 11.8 and 10.5% and 4.2, 5.1 and 5.4% for 1, 3 and 6 scales, respectively. Analyses were carried out on the shape and the form (shape plus size). The Mancova and DA analyses were found to be effective in detecting differences in scale pattern shape between species (except in the case of 3 scales; p=0.079 for the shape and p=0.065 for the form), whereas no differences were recorded between size and sex in all cases. The findings indicate that a good identification of species is possible, with no significant differences when using shape or form. The discriminant analyses provided values of 75.8, 75.0 and 73.4% based on the shape, and of 72.7, 75.8 and 75.0% based on the form, for 1, 3 and 6 scales respectively. Thus, it is possible to obtain a rapid and reliable identification of species using the rhombus of one scale only without considering the size. This is a useful finding in practical terms since scaling requires data on length. In addition, the finding of a suitable discrimination using only the rhombus of one scale raises the possibility of using an ocular adaptor on a camera or mobile, allowing many individuals to be easily screened without having to collect scales.