Otolith shape analysis to discriminate among morpho-ecological groups of Baikal omul (Coregonus migratorius Georgi)

Abstract

Baikal omul (Coregonus migratorious Georgi) is a typical representative of the coregonid fi shes with a complicated intraspecifi c structure consisting of several large and many small populations and three eco-morphotypes. Therefore, it is diffi cult to identify intraspecifi c groups from a mixed catch. Despite basic identifi cation characteristics being well-studied, it is still necessary to identify diagnostic characters for the different intraspecifi c groups. Therefore, we studied differences in the contour shapes of otholiths of omul in specimens from large spawning rivers such as the Verkhnyaya Angara (Upper Angara), Selenga and Bolshaya Rechka. Digitised contour shapes of individual otoliths were analysed based on measurements of a large number of otolith radii, starting from the geometrical centre and measuring 60 equally-spaced radii. Discriminant analysis with step-by-step inclusion of variables (i.e. additional radii) was performed to detect the most informative combination of measurements. Total classifi cation success was 87%. We succeeded in fi nding radii for discrimination of the contour shape in the rostrum, anterostrum, ventral and postrostrum areas. The following areas of sagittae are recommended for diagnostics of morpho-ecological groups of omul: a contour shape of rostrum in the deep-pelagic omul and a contour shape of postrostrum in pelagic and coast-pelagic omul. These studies demonstrate the general usefulness of this technique and its prospects for the discrimination of intraspecifi c groups of coregonid fi shes.