AGE, GROWTH, AND MORTALITY OF GREATER AMBERJACK, SERIOLA-DUMERILI, FROM THE US GULF-OF-MEXICO HEADBOAT FISHERY

Sectioned otoliths (saggitae) from 340 greater amberjack, Seriola dume rili, 305-1512 mm total length (270-1355 mm fork length) were examined . The fish were sampled from recreational headboats operating in the G ulf of Mexico from Naples, Florida, to Port Aransas, Texas, from 1988 to 1993, and therefore, best represent age and growth of the species a s harvested by this fishery. Most (53%) of the fish were landed in Tex as, but others came from northwest Florida and Alabama (46%) and Louis iana (1%). The oldest fish was estimated to be age 15 and measured 151 2 mm total length (1355 mm fork length). Rings formed on most otoliths between March and May, and are thus considered to be true annual mark s. Back-calculated mean total lengths for 225 fish were 415, 614, 742, 839, 915, 976, 1044, 1100, 1156, 1209, 1256, 1283, 1299, 1332, and 13 65 mm for ages 1 through 15, respectively. Equations were derived to c onvert 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: TLt = 1272 (1-e(-0.2272(t+0.7931))), and FLt = 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. Tota l instantaneous mortality estimates (Z) generated from catch curves of the Gulf of Mexico headboat fishery were 0.68 for 1988 and 0.70 for 1 993.