Age and growth of sheepshead (Archosargus probatocephalus) in Tampa Bay, Florida


Brent L. Winner, Timothy C. MacDonald, and Kimberly B. Amendola
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The sheepshead (Archosargus probatocephalus) is common in coastal waters from the Chesapeake Bay to Texas in the United States and supports a viable recreational and commercial fishery throughout much of its range. Otoliths were extracted from 2549 sheepshead collected from 1993 through 2009 in Tampa Bay, Florida, during routine sampling by the Fisheries-Independent Monitoring program of the Florida Fish and Wildlife Conservation Commission. Sheepshead ranged in size from 107 to 524 mm fork length (FL). Age of sheepshead was estimated by counting annuli (opaque zones) in thin-sectioned sagittal otoliths. Marginal-increment analysis of sheepshead from ages 1 to 6 indicated that a single opaque ring was formed on an otolith each year between May and June. In Tampa Bay, sheephead reached a maximum age of 15 years. Males and females experienced rapid growth through age 6; growth rate decreased markedly thereafter. Although von Bertalanffy growth models were biologically similar between sexes, they were found to be statistically different (female [FL=419.1 (1āˆ’eāˆ’0.272(age+1.009))]; males [FL=422.5 (1āˆ’eāˆ’0.255(age+1.115))]). Tampa Bay sheepshead are typically smaller at a given age than those in more northern climates and not as long lived. Differences in regional growth models may be attributed to differences in mortality, ontogenetic shifts in habitat, genetic variation, or sampling design.