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Olfaction in fish is one of the most important chemosensory modalities driving the essential approaches to interact with the encompassing habitat. The olfactory organ of river catfish, Clupisoma garua (Siluriformes; Ailiidae) was studied by employing optical microscopy to delineate the cellular composition in harmony with the annual reproductive cycle. The olfactory epithelium was an intimate folded sheet, sandwiched a thin connective tissue layer, the central core, composed of disposed of connective tissue with nerve fibers and blood vessels through it. A sharp distinction has prevailed between the epithelium and central core by a basement membrane. The thickness of olfactory mucosa with diverse cells was counted attention to their architecture, magnitude, compactness, staining intensity, and distribution patterns throughout altered reproductive phases. In view of the texture of the apical part and outward specialization, the olfactosensory epithelium contained morphologically identified ciliated, microvillous, and rod receptor cells. The non-sensory epithelium was typified by labyrinth cells, mucous cells, mast cells, basal cells, ciliated supporting cells, and non-ciliated supporting cells. They were intermingled in the epithelial lining. The functional emphasis of olfactory cells covering the mucosa was argued with the chemoreception of the fish interested.