University of Isfahan Taxonomy and Biosystematics 3115-9001 15 55 2023 08 23 Investigation of Morphological Changes in Golden Mullet, Chelon auratus (Risso, 1810) from the Southern Caspian Sea Basin using the Geometric Morphometric Technique بررسی تغییرات ریختی ماهی کفال طلایی Chelon auratus (Risso, 1810) در بخش جنوبی حوضۀ دریای کاسپین با استفاده از روش ریخت‌سنجی هندسی 1 18 27024 10.22108/tbj.2022.134542.1209 EN Keivan Abbasi Assistant professor, Inland Waters Aquaculture Research Center. Iranian Fisheries Sciences Research Institute. Agricultural Research, Education and Extension Organization, Bandar Anzali, Iran. 0000-0001-5095-2905 Atta Mouludi-Saleh PhD student of Aquatic Ecology, Faculty of Natural Resources, University of Tehran, Karaj, Iran Soheil Eagderi Associate professor of Fisheroies, Faculty of Natural Resources, University of Tehran, Karaj, Iran Siamak Bagheri Associate professor, Inland Waters Aquaculture Research Center. Iranian Fisheries Sciences Research Institute. Agricultural Research, Education and Extension Organization, Bandar Anzali, Iran Alinaghi Sarpanah Assistant Professor, Iranian Fisheries Sciences Research Institute. Agricultural Research, Education and Extension Organization, Tehran, Iran Akbar Pourgholami-Moghaddam Structure, Inland Waters Aquaculture Research Center. Iranian Fisheries Sciences Research Institute. Agricultural Research, Education and Extension Organization, Bandar Anzali, Iran Journal Article 2022 08 09 During 2020-2021, to investigate the morphological variation of Chelon auratus, a total of 170 specimens were collected using beach seine nets from the shores of Astara (23 specimens), Anzali (33 specimens), Kiashahr (23 specimens), Langaroud (27 specimens), Roudsar (7 specimens), Chalous (30 specimens), Mahmoudabad (14 specimens), and Sari (13 specimens). At the sampling sites, after imaging from the left side of the specimens, 14 landmark points were defined and digitized on the two-dimensional images using the tpsDig2 software. The obtained data, after generalized Procrustes analysis, were analyzed using multivariate statistical analyses including principal component analysis (PCA), canonical variate analysis (CVA), and cluster analysis (CA). The deformation patterns of each population were illustrated in relation to consensus shapes on the deformation grids. The results showed significant differences in the body shape of the studied populations (P<0.05). These differences, related to head length, body depth, dorsal fin position, and caudal peduncle length, suggest the separation of populations in response to environmental conditions. Introduction Golden mullet, Chelon auratus, ranking second in abundance among bony fishes in the southern Caspian Sea basin after Rutilus frisii, constitutes about 20% of the total catch. The study of fish in aquatic ecosystems is crucial for understanding various aspects such as behavior, ecology, evolution, physiology, and stock assessment evaluation. Morphological studies are pivotal in numerous biological processes, including feeding, reproduction, and survival in aquatic ecosystems. They serve as a significant index for habitat selection and swimming behavior, reflecting both habitat conditions and the genetic characteristics of fish. Various methods, including genetics, osteology, growth, fecundity, traditional morphometrics, and geometric morphometrics, are employed to differentiate fish populations. This study, conducted during 2020-2021, investigated the morphological variation of this species by collecting specimens along the coasts of Guilan and Mazandaran provinces, from Astara to Sari. Materials and Methods For this study, 170 specimens of Chelon auratus were collected from the shores of Astara (23 specimens), Anzali (33 specimens), Kiashahr (23 specimens), Langaroud (27 specimens), Roudsar (7 specimens), Chalous (30 specimens), Mahmoudabad (14 specimens), and Sari (13 specimens) using beach seine nets. At the sampling sites, images were taken from the left side of the specimens. Subsequently, in the tpsDig2 software, 14 landmark points were defined and digitized on the two-dimensional images. After conducting generalized Procrustes analysis on the data, multivariate statistical analyses were performed, including principal component analysis (PCA), canonical variate analysis (CVA), and non-parametric multivariate analysis of variance (NPMANOVA) based on P-values obtained from a permutation test (with 10,000 repetitions), as well as cluster analysis (CA). The deformation patterns of each population were visualized relative to the consensus shape in the deformation grids. Findings The results of the principal component analysis (PCA) revealed six components as the main factors contributing to variations among the studied populations. The PCA indicated some overlap between the populations, but the Anzali, Roudsar, and Kiashahr populations were significantly distinct from the Sari and Mahmoudabad populations. The greatest Mahalanobis and Procrustes distances were observed between the Kiashahr and Sari populations. Non-parametric multivariate analysis of variance (NPMANOVA) demonstrated significant differences between the populations, except for Sari-Mahmoudabad and Chalous-Mahmoudabad comparisons. According to the cluster analysis, Chalous, Langaroud, and Sari populations were grouped into one cluster and differentiated from the others. The deformation grids of the body shape of each population revealed significant differences in body shape among the studied populations. The Chalous population exhibited the greatest body depth, whereas the Langaroud population had the least. An upward position of the snout was noted in the Anzali, Kiashahr, Langaroud, Mahmoudabad, and Roudsar populations. Additionally, the Langaroud and Kiashahr populations had shorter caudal peduncles. The Astara population was characterized by a longer snout. The deepest head depth was found in the Astara and Chalous populations, with the Chalous population also displaying a more anterior position of the dorsal and anal fins. Conclusion The results of this study revealed significant morphological differences among the populations of Chelon auratus (P<0.05). The main distinctions were observed in the size of the head, depth of the body, and the positioning of the dorsal fin and caudal peduncle. These differences likely reflect the adaptation of the populations to varying environmental conditions. Considering that both biotic and abiotic factors across different regions of the Caspian Sea basin in Iran vary from slight to moderate, and given that C. auratus is a marine species that migrates north-south and to a lesser extent east-west throughout the year, a lack of complete morphological differentiation between populations from different regions is understandable.

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