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Fishery Bulletin 112(4) 
Figure 2 
Examples of sections of Gulf sturgeon ( Acipenser oxyrinchus desotoi ) used in this study for comparison of 
age structures: (A) fin spine with incorporated fin rays, (B) dorsal-, pelvic-, and anal-fin rays, (C) otolith, 
and (D) second marginal pectoral-fin ray. Fin spines and fin rays were sectioned at 0.3-0. 6 mm and otoliths 
were sectioned at 0.5 mm with an IsoMet low speed saw. Fin spines and second marginal pectoral fin-rays 
provided the clearest banding patterns. Fin rays from the dorsal, pelvic, and anal fins were inconsistent and 
indistinct, and sectioned otoliths provided unreliable banding patterns. Structures for aging Gulf sturgeon 
were collected from sturgeon captured in the Choctawhatchee River in 2010, from archived specimens from 
the Apalachicola and Choctwahatchee rivers in 2010, and from an archive of Gulf sturgeon captured on the 
Suwannee River in 1980-90. 
did those fins with commonly applied external tags 
(Fig. 3, A and B). Removal sites were healed dramati- 
cally in comparison with the sites where fin spines had 
been sampled (Fig. 3C). 
Overall, the second marginal fin ray produced con- 
sistent, clear, and reliable banding patterns. Band 
count comparisons between the second marginal fin ray 
and fin spine showed little systematic bias between the 
structures for counts of up to 25 bands (Fig. 4). Preci- 
sion and PA estimates were high for band counts be- 
tween the fin spine and second marginal fin ray: n- 222; 
CV=0.75%; APE=1.06%; PA-96.46% (±0 band pairs), 
98.23% (±1 band pair), and 100.00% (±2 band pairs). 
Therefore, the second marginal fin ray was considered 
a robust aging structure and appears to be a valid sub- 
stitute for the fin spine for aging analysis. 
