Age-size Structure of Gray Snapper from the Southeastern United States: A Comparison of Two Methods of Back-calculating Size at Age from Otolith Data

The age-size structure of gray snapper (Lutjanus griseus) from Ft. Pierce, Florida, to Grand Isle, Louisiana, was examined. Otolith sections from 432 fish collected in 1991 to 1993 were used to compare 2 methods (direct proportion and regression) of back-calculation of size at age. The observed age range was 1 to 25 years and the size range was 236 to 764 mm total length. Differences were observed in back-calculated sizes at age between the 2 back-calculation methods, between sexes and geographic divisions. The back-calculated size at age was larger for ages 1 to 10 years from the direct proportion than from the regression method. Males were larger than females for ages 4 to 15 years using the direct proportion method, but only for ages 13 and 14 years using the regression method. Northern fish were larger at age than southern fish using both back-calculation methods.

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