Microscopic Characterization of Otolith Abnormalities in Garfish Belone belone (Actinopterygii: Belonidae) from the Black Sea Using Light and SEM Microscopy

Abstract In this study, light microscopy and scanning electron microscopy (SEM) were employed to investigate morphological and structural characteristics of otoliths (ear stones) in garfish Belone belone individuals (n = 190) collected from the Kocaeli (n = 114) and Ordu (n = 76) coasts of the Black Sea. SEM analyses enabled high-resolution imaging of otolith surface microstructures and revealed clear morphological deviations in a subset of specimens. Otolith abnormalities were observed in nine individuals, with a regional frequency of 3.5% in Kocaeli and 6.58% in Ordu. While normal otoliths displayed consistent aragonite crystal patterns and elliptical morphology with defined mesial and lateral surfaces, abnormal otoliths showed irregular growth patterns, asymmetry, and disrupted surface architecture, particularly on the lateral surface. Morphometric measurements such as length, width, area, perimeter, and weight indicated significant differences between normal and abnormal otoliths (p < 0.05), especially in the Ordu samples. SEM provided detailed evidence of altered biomineralization in abnormal otoliths, suggesting possible environmental or developmental influences. These results highlight the utility of integrated microscopy techniques in identifying subtle structural anomalies and contribute to a deeper understanding of otolith formation and variability in marine teleosts. The combined use of SEM and light microscopy proves essential for comprehensive microstructural characterization in fish biomineral studies.