Regional Variation in the Population Structure of Gray Snapper, Lutjanus Griseus, along the West Florida Shelf
We examined variation in life history traits of gray snapper [Lutjanus griseus (Linnaeus, 1758)] from three regions along the west Florida shelf with varying levels of fishing pressure. A total of 1132 gray snapper 254–724 mm TL were sampled from recreational and commercial fisheries. Overall the ratio of females to males was not significantly different from 1:1. Mean size decreased from north to middle to south (commercial 489–441 mm TL; recreational 501–345 mm TL). Gray snapper ages ranged from 2 to 26 yrs. Mean age decreased from north to middle to south (8.4 to 6.1 to 4.6 yrs) for the recreational fishery, while mean age in the commercial fishery was greatest in the middle region (9.4 yrs) and similar in the north (7.9 yrs) and south (7.6 yrs). Mean size-at-age for the most common ages (5–12 yrs) decreased from north to south. Von Bertalanffy growth curves differed between sexes with a greater L∞ for males. Instantaneous mortality increased from north to south with the largest difference in the recreational fishery (Z = 0.14–0.55). Instantaneous natural mortality (M) estimates varied greatly by the method used (0.17–0.36): Hoenig's estimate of M using a maximum age of 26 yrs was 0.17; the Ralston estimate was 0.36 and the Pauly estimate was 0.24. Observed regional differences in size and age distributions as well as in growth and mortality rates are likely due to differences in exploitation rate.
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Document Type: Research Article
Publication date: 2009-05-01
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