Winner et al.: Age and growth of Archosargus probatocephalus in Tampa Bay, Florida 
161 
Figure 4 
Median monthly percent marginal increment (indicated by black points) for otoliths of 
sheepshead (Archosargus probatocephalus) collected in Tampa Bay, Florida, 1995-1998, by 
individual age classes: (A-F) ages 1-6. Vertical lines represent the interquartile ranges, 
and numbers above percent marginal increments represent the sample sizes. Months of 
minimal marginal increment (indicating annuli deposition) are highlighted in gray boxes. 
ittae of sheepshead from other areas. Studies from 
Louisiana (Beckman et al., 1991), northwest Florida 
{Dutka-Gianelli and Murie, 2001), and South Carolina 
(individual age classes, <age 5; Wenner®) used margin¬ 
al-increment analysis to validate the deposition of a 
single annulus per year. Chemical marking with oxy- 
tetracycline validated the annual deposition of a single 
opaque ring in sheepshead of ages 2-3 (Dutka-Gianelli 
and Murie, 2001). Each of these studies reported that 
a single annulus was deposited from late winter to 
spring (March-May for sagittae)—a finding similar to 
that of our study (May-June). 
In our study, fish older than age 7 were uncommon; 
therefore, we could not analyze marginal increments for 
those fish by age class to validate annulus deposition. 
Examination of fish aged 7-14, as a group, showed that 
annuli formed at the same time as fish in younger age 
classes. Although we presume that these older fish laid 
down a single opaque ring each year, ages of fish older 
than age 6 may sometimes have been misinterpreted 
(Beamish and McFarlane, 1983). It would be valuable 
in future studies in the Tampa Bay area that more age 
data be collected from larger and older sheepshead to 
further elucidate annulus deposition in these older fish. 
