ISSN 1062-3590, Biology Bulletin, 2017, Vol. 44, No. 8, pp. 952–959. © Pleiades Publishing, Inc., 2017. Original Russian Text © P.K. Afanasyev, A.M. Orlov, A.Yu. Rolsky, 2017, published in Zoologicheskii Zhurnal, 2017, Vol. 96, No. 2, pp. 192–200. 952 Otolith Shape Analysis as a Tool for Species Identification and Studying the Population Structure of Different Fish Species P. K. Afanasyev a, *, A. M. Orlov a, b, c, d, **, and A. Yu. Rolsky e, *** a Russian Federal Research Institute of Fisheries and Oceanography, Moscow, 107140 Russia b Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, 119071 Russia c Dagestan State University, Makhachkala, 367000 Russia d Tomsk State University, Tomsk, 634050 Russia e Knipovich Polar Research Institute of Marine Fisheries and Oceanography, Murmansk, 183038, Russia *e-mail: afanasiev@vniro.ru **e-mail: orlov@vniro.ru ***e-mail: rolskiy@pinro.ru Received January 12, 2016 Abstract⎯An analysis and a comparison of the methods of geometric morphometrics as applied to fish spe- cies identification and to studies on the population structure of fish stocks based on peculiarities of the otolith shape are performed. A review of the geometric morphometric methods used in studies on fish otoliths is pro- vided. The results of our own research on possible utilization of elliptical Fourier analysis for species identi- fication are also described. Keywords: geometric morphometrics, otolith morphometrics, otolith shape analysis, species identification DOI: 10.1134/S1062359017080027 INTRODUCTION In recent years, geometric morphometric methods have increasingly widely been used in biological research. Their attractiveness and value have been confirmed by a large number of publications in this field and are currently of no doubt (Adams et al., 2004; Campana, 2005). The majority of works based on the geometric morphometric methods describe the results of studies of two-dimensional images of three- dimensional objects because of the high cost of equip- ment such as 3D scanners, which are required for direct digitization of objects in three dimensions. Until recently, two different approaches—quanti- tative analytical and representational (in a sense, “qualitative”) geometric (Pavlinov and Mikeshina, 2002)—existed and were developed simultaneously in this field. Geometric morphometric methods repre- sent the comparison of the shapes of objects studied. Today, geometric morphometric methods are widely used in studies of fish as a whole object (Man- dritsa, 2007), as well as in comparative studies of bones (Baranov, 2013), otoliths (Svetocheva and Erik- sen, 2013; Campana, 1993), scales (Richards and Esteves, 1997; Ibanez and O’Higgins, 2011; Ibanez, 2014), etc. The comparison of the otolith shape in fish by geometric morphometric methods (so-called “oto- lith shape analysis”) is widely used to study the popu- lation structure of different fish species (Jonsdottir et al., 2006; Schulz-Mirbach et al., 2008; Stransky et al., 2008, 2008a; Treinen-Crespo et al., 2012; Orlov and Afanasyev, 2013; Valentin et al., 2014; Harbitz and Albert, 2015; Cresson et al., 2015). It should be noted that the vast majority of studies on the use of this approach were performed by foreign researchers. In this study, we attempted to review the methods that are currently used to compare the otolith shape and their possible applications in studies of the taxo- nomic status and population organization of different fish species in order to popularize them among Rus- sian researchers. MATERIALS AND METHODS We studied samples of otoliths of seven fish species, which are listed in Table 1. In the analysis we used only the right otolith with- out visible signs of damage (chips, bruises, cracks, ros- trum damage, etc.). Otoliths were preliminarily washed and dried and then photographed with a Nikon D800 digital camera fixed on a tripod. The oto- lith shape analysis was performed using the Shape v. 1.3 software (Iwata and Ukai, 2002). An object with a set size (a square of 5 × 5 mm) was drawn on an oto- lith image using a graphical editor, which made it pos-