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Fishery Bulletin 1 12(4) 
Table 3 
Mean rate and range of jackknife reclassification success, standard error of the mean (SE), null expecta- 
tions, and predictor variables associated with 3 discriminant function analyses that examined otoliths 
from female southern flounder ( Paralichthys lethostigma ) collected in 1996 and in 2009-2012 in the 
South Atlantic (North Carolina, South Carolina, Georgia, and Florida) and the Gulf of Mexico (Florida, 
Alabama, Mississippi, Louisiana, and Texas) as part of state or federal agency sampling programs and 
from seafood dealers. EFC=elliptical Fourier coefficients; g=number of groups. 
Basin 
Within 
Atlantic 
Within 
Gulf of Mexico 
Within 
North Carolina 
Mean reclassification success 
0.79 
0.47 
0.66 
0.47 
Reclassification success range 
0.74-0.84 
0.38-0.56 
0.53-0.77 
0.39-0.55 
SE 
<0.01 
<0.01 
<0.01 
<0.01 
Expected mean (1 lg) 
0.50 
0.33 
0.50 
0.33 
Expected range 
0.45-0.56 
0.25-0.41 
0.40-0.60 
0.26-0.40 
Predictor variables 
Ellipticity 
Form function 
Aspect ratio 
10 EFCs 
10 EFCs 
Form function 
10 EFCs 
Form function 
10 EFCs 
ronmental conditions and growth rates can be major 
determinants of changes in otolith shape (Campana and 
Casselman, 1993; Cardinale et al., 2004), we presumed 
that young southern flounder would most likely reflect 
the regionally different environments (if sufficient vari- 
ability existed regionally) and, therefore, would make 
good candidates with which to detect the effects of 
those differences on their otolith shape. For instance, 
if spatial differences existed in growth conditions that 
were sufficient to generate distinct otolith shapes, then 
they should be greatest in younger fish at the end of 
the estuarine phase, when confidence in the spatial 
segregation of fish is high and the fish are growing rap- 
idly while occupying habitats in which local conditions 
can cause variability in growth. Although variability in 
fine-scale processes, such as recent feeding history, has 
been shown to be an important determinant of otolith 
shape (Gagliano and McCormick, 2004; Hussy, 2008), 
it was not practical for us to consider smaller spatial 
scales given the uncertainty in habitat use beyond the 
system of capture. 
Considerable mixing of individuals from broadly 
separated areas during some phase of their life his- 
tory also would dampen within-basin and within-state 
environmental effects on otolith shape. Once they 
mature, southern flounder emigrate from estuaries 
to participate in offshore spawning. Within the U.S. 
South Atlantic, individuals can migrate considerable 
distances (e.g., North Carolina fish recaptured in Flor- 
ida; Monaghan 7 ; Craig and Rice 8 ), and therefore mixing 
of fish from different regions within the basin may be 
considerable. Therefore, despite the fact that, prior to 
maturity, many southern flounder likely occupy small 
home ranges in specific estuaries that span environ- 
mental gradients sufficient to generate differences in 
growth and otolith shape, a high degree of offshore 
mixing could result in a level of genetic homogeniza- 
tion that swamps local environmental effects. 
One additional and less discussed factor that possi- 
bly affects otolith shape is time of capture. To minimize 
variation in body size, all of our fish were collected dur- 
ing late summer and fall. Each of the age-1 females 
that we used in this study, therefore, had the oppor- 
tunity to take advantage of the warm summer grow- 
ing season, a factor that helped to reduce size vari- 
ability in our sample. However, this time of capture 
meant that our samples were taken near the end of a 
period of rapid otolith growth. In addition to the no- 
tion that otolith shape is less variable as fish age and 
mature (Campana and Casselman, 1993), Gauldie and 
Nelson (1990) also found that faster otolith growth (of- 
ten occurring among the youngest age groups) resulted 
in long, thin aragonite crystals. Therefore, it is pos- 
sible that periods of fast otolith growth can result in a 
wider variety of otolith shapes present within a stock, 
making distinctions less apparent among younger age 
groups. We were not able to address this possibility in 
our study because southern flounder of older ages are 
encountered much less frequently in estuarine waters 
than in offshore waters. 
Implications for management 
Our examination of variation of otolith shape to de- 
tect the population structure of southern flounder at 
3 geographic scales has possible implications for man- 
agement. The combination of established genetic dif- 
ferentiation (Anderson et ah, 2012) and the high like- 
