Morphological Features of the Otoliths of the Sailfish, Istiophorus platypterus , Useful in Age Determination

In this study 65 sailfish were analyzed and the morphology of the otoliths described. A mathematical relationship between the wet weight of the fish and morphological features of the sagitta enabled the estimation of the age of all but one specimen. Ages of very large fishes, previously difficult to measure were readily amenable to otolith age analysis. The internal and external otolith structures, viewed with scanning eletron microscope (SEM) appeared to show an annual periodicity and provided data that are not available by other means. With this data it is possible to determine a growth rate and age estimate for all sizes of the sailfish sampled, including larger fish that were difficult to age in the past.