Age, Growth, and Mortality of Greater Amberjack, Seriola Dumerili, from the U.S. Gulf of Mexico Headboat Fishery

Sectioned otoliths (saggitae) from 340 greater amberjack, Seriola dumerili, 305-1512 mm total length (270-1355 mm fork length) were examined. The fish were sampled from recreational headboats operating in the Gulf of Mexico from Naples, Florida, to Port Aransas, Texas, from 1988 to 1993, and therefore, best represent age and growth of the species as harvested by this fishery. Most (53%) of the fish were landed in Texas, but others came from northwest Florida and Alabama (46%) and Louisiana (1%). The oldest fish was estimated to be age 15 and measured 1512 mm total length (1355 mm fork length). Rings formed on most otoliths between March and May, and are thus considered to be true annual marks. Back-calculated mean total lengths for 225 fish were 415, 614, 742, 839, 915, 976, 1044, 1100, 1156, 1209, 1256, 1283, 1299, 1332, and 1365 mm for ages 1 through 15, respectively. Equations were derived to convert lengths: FL = -17.7319 + 0.8847(TL), and TL = 24.2327 + 1.1247(FL). Back-calculated lengths at age were used to derive the following von Bertalanffy growth equations: TL_t = 1272 (1-e^{-0.2272(t+0.7931)}), and FL_t = 1109 (1-e^{-0.2270(t+0.7198)}). Greater amberjack are fully recruited to the headboat fishery in the Gulf of Mexico at age 4. Total instantaneous mortality estimates (Z) generated from catch curves of the Gulf of Mexico headboat fishery were 0.68 for 1988 and 0.70 for 1993.