Comparative study on Scale Morphology of two cyprinid fish Cyprinus carpio and Catla catla

Fish scales display various characteristics features like position of focus, number of radii, appearance of circuli which could be helpful in identification of fishes. The present study comparatively investigated the scale morphology of two commercially important cyprinid fishes, Cyprinus carpio and Catla catla. A total of 40 specimens of C. carpio and 30 specimens of C. catla (15–30 cm total length) were collected from fish markets of Gazipur (Delhi) and Yamunanagar (Haryana), India. Scales were sampled from four body regions, namely the predorsal region, basal region, below the dorsal fin, and lateral line region. After cleaning with 1% KOH, scales were examined under a stereomicroscope to document variations in shape, position of the focus, arrangement of circuli, distribution of radii and margin morphology. Both species possessed cycloid scales; however, distinct interspecific differences were observed in scale shape, focus position, radii distribution, and anterior and posterior margin characteristics across different body regions. Cyprinus carpio predominantly exhibited cordate scales with centrally positioned focus and smooth anterior margins, whereas Catla catla displayed round-squarish or ovoid scales with an anteriorly positioned focus and characteristic wavy anterior margins. The lateral line scales of both species contained a well-developed longitudinal canal but differed in overall morphology. These findings demonstrate that scale micro-morphological characters are reliable diagnostic features for distinguishing closely related cyprinid species and can complement conventional taxonomic approaches. The study highlights the significance of comparative scale morphology in fish systematics, biodiversity assessment and fisheries research.