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RECRUITMENT DYNAMICS AND OTOLITH CHEMICAL SIGNATURES OF JUVENILE GRAY SNAPPER, LUTJANUS GRISEUS, AMONG WEST FLORIDA ESTUARINE AND COASTAL MARINE ECOSYSTEMS
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RECRUITMENT DYNAMICS AND OTOLITH CHEMICAL SIGNATURES OF JUVENILE GRAY SNAPPER, LUTJANUS GRISEUS, AMONG WEST FLORIDA ESTUARINE AND COASTAL MARINE ECOSYSTEMS

Cecelia Lounder
University of West Florida
Master of Science (MS), University of West Florida
2009

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Abstract

A hierarchical approach to examine nursery function of coastal systems was tested for gray snapper, Lutjanus griseus. Juveniles were sampled with trawls and seines in four regions along west Florida. The first two tiers of habitat evaluation showed that seagrass was a significant variable for presence/absence and density of gray snapper (Binomial GLM; p < 0.001, Delta Lognormal GLM; p = 0.002). Significant differences in growth rates were observed in 2007 (ANCOVA test for equal slopes; p < 0.001) but not 2006, driven by fastest growth in the Southwest region and slowest in the Big Bend region. Region-specific natural tags from otolith chemistry were derived from element:Ca ratios (Ba:Ca, Li:Ca, Mg:Ca, Mn:Ca, and Sr:Ca) and carbonate stable isotopes values (13C and 18O). Significant differences were found among study regions and between sampling years (MANOVA Pilia's trace; p < 0.001 for both effects). Cross validated classification accuracies using four regions were 77.9% in 2006, 85.0% in 2007, and 76.3% when years were modeled jointly. Using three regions raised classification success to 82.6% in 2006, 92.3% in 2007, and 83.3% when years were modeled jointly. Subsequent studies may employ tags based on otolith chemical signatures to estimate nursery sources of adults.
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