Abstract

King mackerel, Scomberomorus cavalla, is one of the more targeted fishes in the US south Atlantic and Gulf of Mexico (GOM). Accurate assessment of the status of Atlantic and GOM stocks requires comprehensive knowledge of population ecology parameters such as growth and population connectivity.   We have been conducting research aimed at improving knowledge of those parameters, with a particular emphasis on estimating population connectivity during winter in south Florida.  In summer 2006, we sampled 441 individuals from the Atlantic and 502 from the northeastern GOM.  Atlantic fish ranged in size from 90 mm to 1,320 mm and age from 0 to 19 years, while ranges for GOM size and age were 91 mm to 1505 mm and 0 to 20 years, respectively.  Von Bertalanffy growth equations computed from otolith-based age estimates were different between stocks and sexes.  Otoliths of summer sampled fish were digitized and Fourier analysis of their morphology was conducted to compute stock-specific natural tags based on otolith shape.  Otolith shape was significantly different between sexes and stocks (MANOVA, p < 0.001).   Results of linear discriminant function analysis indicated shape parameters distinguished Atlantic and GOM fish but only with modest classification success (mean jackknifed classification accuracy = 66.0%).  Natural tags based on otolith shape parameters then were applied to estimate the stock identity of king mackerel harvested in three regions around southern Florida in winter 2006/07 with maximum likelihood stock mixing models.  Results indicated a longitudinal gradient existed in Atlantic stock contribution to winter mixed stock fisheries with highest Atlantic contribution in southeastern Florida and lowest in southwestern Florida. Overall, our results provide further evidence that the practice of assigning all south Florida winter landings to the GOM stock is not accurate and should be re-evaluated

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