Title

Age and growth of cobia, Rachycentron canadum, from the northeastern Gulf of Mexico

Document Type

Article

Publication Date

7-1-1999

Department

Marine Science

Abstract

We examined 1005 cobia, Rachycentron canadum, from recreational catches in the northeastern Gulf of Mexico from 1987 to 1995. Specimens ranged from 325 to 1651 mm fork length (FL); females had a mean FL of 1050 mm (n=730) and were significantly larger than males that had a mean FL of 952 mm (n=275). The over all male to female ratio was 1:2.7. Ages of 565 cobia were estimated from thin-sectioned otoliths (sagittae). Marginal-increment analysis of sagittal otoliths showed a single annual minimum during June. Male cobia (n=170; 525-1330 mm FL) ranged from age 0 to 9, and females (n=395; 493-1651 mm FL) ranged from age 0 to 11. The relationship of observed fork length and age was described by the von Bertalanffy growth equation for males FLt = 1171(1-exp [-0.432(t+1.150)]) and for females FLt = 1555(1-exp [-0.272(t+1.254)]). Growth in length for both sexes was relatively fast through age 2, after which growth slowed gradually. Estimates of the von Bertalanffy growth equation parameters L-infinity and K were significantly different for males and females, whereas estimates for t(0) were not significantly different. Sagittal otolith weight was a good predictor of age. The instantaneous rate of total mortality (Z) estimated by catch curve analysis for fully recruited ages 4-8 was 0.75.

Publication Title

FISHERY BULLETIN

Volume

97

Issue

3

First Page

459

Last Page

471