280 
Fishery Builetin 112(4) 
Figure 5 
Sectioned second marginal pectoral-fin ray of a Gulf sturgeon ( Acipenser oxyrinchus 
desotoi) (A) under UV light and (B) under natural light. Both images show the same 
sturgeon one year after it was captured and marked chemically with oxytetracycline 
(OTC). The fluoresced mark, indicated by the arrow, shows the marking incorporated 
on the initial capture date of 8 October 2009. Red dots indicate band pairs and show 
that, by the recapture date of 11 October 2010, one complete band pair had formed 
after the chemical mark. Both capture events occurred in the Choctawhatchee River. 
ary of that year had 15 band pairs; a partially formed, 
translucent band was evident after the chemical mark. 
However, fin rays from 8 other recaptured sturgeon did 
not fluoresce under UV light. This outcome indicates 
that OTC was not incorporated into the bony struc- 
tures of many of the Gulf sturgeon that were injected 
with it and that doses may have been too low for vali- 
dation purposes. 
Discussion 
The second marginal pectoral-fin ray is not an un- 
known structure for age and growth studies, although 
its use as a primary aging structure has not been 
discussed previously. Brennan and Cailliet (1989) 
noted that bands from this fin ray were consistent 
with the bands from fin spines but did not evalu- 
