We sampled yellowtail snapper, Ocyurus chrysurus, from commercial and recreational fisheries and fishery-independent surveys in the Atlantic Ocean off south Florida from 1980 through 2002. Specimens were collected primarily from two areas: Palm Beach and Monroe counties; collections were divided at 26° latitude into northern and southern populations. We collected sagittal otoliths and corresponding morphometric data from each population. Fork lengths (FL) ranged from 115 to 605 mm with a mean length of 312 mm. Yellowtail snapper were aged using sagittal otoliths with a high degree of precision [average percent error (APE) \u3c1%]. Ages ranged from 1 to 17 years, with mean ages of 3.96 years for the commercial fishery, 3.33 years for the recreational fishery, and 3.00 years for fishery-independent surveys. Yellowtail snapper entered the commercial and recreational fisheries by age 2; both fisheries were dominated by 2 and 3 year olds. The commercial fishery indicated the influence of a strong 1994 year class; this was not apparent in the recreational and fishery-independent surveys possibly due to small sample size. The von Bertalanffy growth curve parameters for all years and fishing modes combined [Lt = 410(1 - e-0.27(t+2.03))] were similar to previously published estimates for yellowtail snapper. The instantaneous total mortality rate of yellowtail snapper for all years and fishing modes combined (Z = 0.49) was also similar to previously published estimates. The total mortality rate for the northern population, Z = 0.67, was greater than for the southern population, Z = 0.45. Weight-length relationships were significantly different between northern and southern populations (P \u3c 0.001), and yellowtail snapper from the southern population were significantly larger and older than those from the northern population (P \u3c 0.001). Size-at-age was significantly larger for the most common ages (1--4 years) in the northern population compared to the southern population (age 1, P = 0.002; age 2--4, P \u3c 0.001 ). This may be due in part to differential fishing pressure; additional site-specific sampling is needed to elucidate the demographic differences between populations
