Otolith microstructures of Vinciguerria nimbaria from the tropical Atlantic Ocean were examined in an attempt to explain the peculiar behaviour of this small mesopelagic fish species. One part of the population forms schools near the surface during the day while the other part makes diel migrations between the surface (night) and the deep waters (day). Thin transverse sections of the otolith (10-40 ?m thickness) showed an extremely clear succession of daily-like microincrements along the dorsal and ventral axis. However, no validation of the frequency of microincrement deposition has been undertaken on this fragile species. Five distinct growth zones were observed along the otoliths of all individuals, representing some common life history events during larval stages, metamorphosis, and juvenile and adult stages. The lifespan is probably very short (120-150 microincrements counted, with a maximum of 240), probably less than 1 year. No differences in growth patterns were recorded between migrating and non-migrating individuals.
