Age distribution and growth of greater amberjack, Seriola dumerili, from the north-central Gulf of Mexico


Thompson, Bruce A., Marty Beasley, and Charles A. Wilson
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The lack of age and growth estimates and population parameters for the amberjack family prompted our study to describe otolith structure and determine size-at-age and growth rates of greater amberjack (Seriola dumerili) from the north-central Gulf of Mexico. Greater amberjack age and growth was described from a combination of external ridges and internal annuli in sectioned sagittal otoliths. A mark-recapture study using tetracycline was consistent with a single annulus being formed each year in two- and three-year-old amberjack. Tag-recapture data from the Gulf of Mexico and South Atlantic Cooperative Gamefish Tagging Program also confirmed that a single annulus increment was formed each year. Ages for 597 specimens ranged from young-of-the-year to 15 years, and all fish over 9 years were female. Sagittal weight provided a reliable estimation of fork length with a relationship of FL = 151 (1 – e (–0.04(SW+1.6))): a negative exponential equation in the form of the von Bertalanffy equation. The fit of the negative exponential in this application provides evidence of the disassociation between otolith growth and fish growth as fish age. The von Bertalanffy growth curve equation, Lt = 138.9 (1 – e–0.25(t+0.79)), compared favorably with previous published values. Monthly changes in size and availability indicate a Gulf-wide migration of this moderately long-lived pelagic predator.