<p>The arrangement of the sensory epithelium over the surface of the olfactory lamellae in teleosts is variable, with a diverse pattern ranging from large expanses of continuous epithelium to numerous discrete islets. As the olfactory epithelium is the location where water-borne odorants interact with olfactory receptors, its spatial distribution pattern serves as an important anatomical proxy for olfactory ability. However, nothing is known about the olfactory epithelial pattern in southern bluefin tuna, <i>Thunnus maccoyii</i>. Scanning electron microscopy was used to examine the spatial distribution pattern, area, and number of olfactory epithelial patches over the olfactory lamellar surface within the olfactory rosettes of both juvenile and mature <i>T. maccoyii</i>. Juvenile <i>T. maccoyii</i> exhibit a novel olfactory epithelial topography, where the lamellae in the caudal parts of the olfactory rosette display a combination of Type IV (olfactory epithelium arranged into numerous, small discrete islets) and Type III (olfactory epithelium irregularly intermingled with non-sensory epithelium) topographies. The lamellae in the rostral parts of the olfactory rosettes primarily have Type IV topography. In both arrangement patterns, the olfactory epithelia are smaller and more numerous rostrally. In mature <i>T. maccoyii</i>, the Type IV topography disappears, and lamellae in all parts of the olfactory rosette display exclusively Type III topography. The combined results of this study reveal a new and unique distribution pattern of olfactory sensory epithelia in <i>T. maccoyii</i>, with a striking change in distribution pattern associated&#xa0;with both lamellar location and growth, indicating adaptation to the different hydrodynamic conditions.</p>