158 
Fishery Bulletin 115(2) 
Table 1 
Descriptive statistics for fork length and age (mean, minimum, maximum, and standard deviation [SD]) and total 
catch of sheepshead (Archosargus probatocephalus) collected in Tampa Bay, Florida, in 1993—2009, by gear type. 
Fork length (mm) Age (years) 
Gear type 
Number of fish 
Mean 
Min 
Max 
SD 
Mean 
Min 
Max 
SD 
Small haul seines 
52 
287.0 
153 
415 
65.2 
3.5 
0.9 
6.9 
1.6 
Large haul seines 
1931 
299.4 
107 
524 
63.7 
4.1 
0.5 
15.2 
2.1 
Purse seines 
50 
256.1 
173 
465 
62.3 
3.1 
1.2 
7.9 
1.6 
Gill nets 
62 
284.2 
158 
409 
59.3 
3.7 
1.0 
9.6 
2.0 
Otter trawls 
36 
254.6 
159 
383 
55.7 
3.4 
1.3 
11.6 
2.3 
Trammel nets 
367 
322.9 
146 
458 
48.3 
4.5 
0.6 
11.5 
1.8 
Unknown 
51 
318.2 
190 
433 
52.8 
4.8 
1.3 
10.5 
1.7 
Total catch 2549 
100 
w 
(D 
XJ 
£ 
3 
75 - 
50 - 
25 - 
0 - 
25 - 
50 - 
75 - 
100 
Females 
I Retained (n=1350) 
I Excluded (n=75) 
Males 
Retained (0=730) 
Excluded (n=64) 
100 
150 
200 
250 
300 
350 400 450 500 
Fork length (mm) 
Figure 2 
Length-frequency distributions for female and male sheepshead {Ar¬ 
chosargus probatocephalus) collected in Tampa Bay, Florida, 1993- 
2009. Sheepshead that were retained and excluded (otolith identified 
as unreadable) from the age and growth analysis are depicted. Sheeps¬ 
head for which there was both age and sex information but which did 
not have a measured fork length were excluded from this plot 
where Lt = the observed FL at time t, 
= the asymptotic FL; 
k = the growth coefficient; 
t = the observed age; and 
to = the hypothetical age at size zero, was fit by 
nonlinear regression (Proc NLin procedure, 
Marquardt routine in SAS software) for 
sex-specific observed age and length data. 
Growth models for males and females 
were compared with an approximate ran¬ 
domization test (Helser, 1996). 
Results 
Size and sex composition 
Sheepshead (n=2549) ranging in size 
from 107 to 524 mm FL were collected in 
Tampa Bay (Fig. 1) with a variety of gear 
types (Table 1). Although sampling was 
done throughout the estuary, most speci¬ 
mens were collected along the shoreline 
in the middle to lower portions of the 
estuary with a large haul seine (n=1931, 
75.8%) or a trammel net {n=367, 14.4%). 
Together, the other gear types caught 
less than 10% of the specimens used in 
this study. 
Sex was determined for 93% of the 
sheepshead collected. The majority of 
the specimens for which sex was not de¬ 
termined were immature (<2 years old) 
fish for which gonad samples were too 
small to allow sex determination. The 
sex ratio of males to females (1:1.75) in 
our samples was significantly different 
from 1:1 (G-test: 177.69, df=l, P<0.001). 
Mean length of females (308.5 mm FL) 
was slightly greater than that of males 
(302.0 mm FL), but length-frequency dis¬ 
tributions did not differ significantly between sexes 
(Fig. 2; KS test: 0.058, P>0.05). Neither the slopes nor 
the intercepts differed significantly in the sex-specific 
length-length regressions (ANCOVA: P>0.05); there¬ 
fore, all sheepshead data were pooled to elucidate 
relationships among SL, FL, and TL (Table 2). All 
length-length regressions exhibited high coefficients of 
determination (r2>0.988) (Table 2). Sex-specific length- 
550 
