Abstract

Cobia, Rachycentron canadum, are migratory, coastal pelagic fish that are distributed worldwide in tropical and subtropical seas, except forthe eastem Pacifico Previous research established that cobia from the northern Gulf of Mexico recreational fishery could be exactly aged using sectioned sagittal otoliths. The collection of sagittae from cobia harvested by fishers typically requires removal of the entire head for subsequent otolith extraction and sectioning in the laboratory, often a difficult and time consuming process. We conducted a comparison of age estimates obtained from analyses of whole and sectioned sagittal otoliths and sectioned first dorsal spines. Whole sagittae contained growth zones assumed to be annual events, and dorsal spine sections revealed a succession of altemating opaque and translucent bands that, although not validated as annuli, were used in age estimations. Vascular erosion of the central core of spines from some large fish obscured the inner (early) growth bands which required their statistical replacement The accuracy of age estimates from readings of whole sagitta and dorsal spine sections was as certained by comparison with age data from sectioned sagittae from the same fish. Although more difficult to collect, sagittae provide more detailed age information, however, dorsal spines are more practical in terms of ease of collection and may represent an altemative for deriving age estimates for cobia.

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