Fishery-specific age and growth of greater amberjack in the Gulf of Mexico, with application of fin-rays for ageing tag-and-released fish

Greater amberjack Seriola dumerili in the Gulf of Mexico are overfished, yet their population dynamics are still poorly understood and age and growth over most of its exploitation range is unknown. In cooperation with state and federal fisheries agencies in the southeastern U.S., a total of 1,838 fish from 74 to 1829 mm fork length were collected during 1989 to 2008 and sagittae were extracted for aging. Ages and growth were compared for charterboat, private recreational, headboat, and commercial fisheries in the Gulf, as well as fishery-independent sampling. Greater amberjack ranged in age from young-of-year to 15 years, and females >4 years old were larger at age than males.  Growth of greater amberjack was similar for private, charter, and headboat fisheries.  The commercial hook-and-line fishery caught the largest individuals in a cohort for ages 1-4, in conjunction with a greater minimum size regulation. A subsample of amberjack in 2006-2008 also had pectoral finrays removed for aging to develop both a quicker method of port-sampling these large fish, as well as a non-lethal aging method for tag-and-release studies. Ages assigned indicated that finrays were relatively precise (average percent error = 7.8%, Lin’s correlation coefficient = 0.908), and with further development for older fish the method could be used to non-lethally age greater amberjack.