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Fishery Bulletin 103(2) 



begin as early as December and proceed through May. 

 Opaque zone formation beginning in December through 

 spring has been shown to occur in the congeneric red 

 snapper (Render, 1995; Patterson et al., 2001; Wilson 

 and Nieland, 2001) as well as in a number of other tele- 

 osts in the northern GOM (Beckman et al., 1989, 1990, 

 1991; Thompson et al., 1999). Burton (2001) validated 

 the periodicity of opaque zone formation for gray snap- 

 per along the Atlantic coast but reported the period of 

 formation to occur during the summer months of June 

 and July. 



The natural decay of radiocarbon in the world ocean 

 after the nuclear testing period is well documented 

 (Broecker et al., 1985) and close agreement between 

 gray snapper data and existing radiocarbon chronolo- 

 gies from the Gulf of Mexico, U.S. South Atlantic, and 

 Caribbean provided additional evidence that our otolith- 

 section-based age estimates of gray snapper were valid 

 (Fig. 3). The 14 C values obtained from gray snapper 

 otolith cores formed after the period of atmospheric 

 testing of nuclear weapons were comparable to, if not 

 slightly less than, those values found in red snapper 

 from the northern Gulf of Mexico (GOM) (Baker and 

 Wilson, 2001). 



Although published coral radiocarbon chronologies 

 are available for review and are made available in the 

 present study, we are most confident in comparing gray 

 snapper to the red snapper data for several reasons. 

 First and foremost, these two species were collected 

 from the same general area of the northern Gulf of 

 Mexico and thus in theory should have similar radio- 

 carbon chronologies (Broecker et al., 1985). Second, 

 although the coral samples would seem to be the best 

 possible items for comparison because of their known 

 age, stationary location, and most importantly because 

 multiple "birth dates" can be analyzed from one coral 

 head, the gray snapper and red snapper samples were 

 taken from different geographic areas and thus differ- 

 ent water bodies. No known coral radiocarbon chronolo- 

 gies exist for the northern Gulf of Mexico. Radiocarbon 

 chronologies have been shown to vary significantly in 

 the world ocean by latitude (Broecker et al., 1985) and 

 this trend in the reference corals can be seen in Fig- 

 ure 3, especially during the period of rapid radiocarbon 

 uptake (1958-75). Finally, all otolith samples (gray 

 snapper and red snapper) were analyzed for radiocarbon 

 by the same AMS facility by using identical laboratory 

 methods (Baker and Wilson, 2001). Delta 14 C data from 

 the otoliths of gray snapper with presumed YOB back 

 to 1973 (the oldest fish in our data set) clearly reflected 

 the same pattern found in red snapper; high levels of 

 oceanic radiocarbon attributable to previous nuclear 

 testing followed by a slow but steady decline to a low 

 in 1995 (Fig. 3). The gray snapper curve is slightly 

 lower but parallel to the red snapper curve. Because 

 of the inherent variability associated with individual 

 fishes, it is inconceivable to think that the two species 

 of snapper would have curves that completely lie on top 

 of each other or on top of the coral chronologies for that 

 matter. Although the two species are very similar in 



many regards, we can only speculate that differences 

 in juvenile life history patterns, habitat preferences, 

 water column chemistry, and possibly otolith formation 

 may account for the variation in radiocarbon chronolo- 

 gies. However, both the gray snapper and previously 

 validated red snapper chronologies exhibit the same 

 trend and indicate that our otolith-based age estimates 

 are accurate. 



The majority of radiocarbon fisheries age validation 

 has produced otolith-based chronologies that resemble 

 those from nearby reference corals or other fish species 

 in the same general location (Campana, 2001). Cam- 

 pana and Jones (1998) observed extremely high and 

 erratic radiocarbon values for black drum (Pogonias 

 cromis) in the Chesapeake Bay. In that study, the ra- 

 diocarbon values resembled the intermediate of surface 

 oceanic (corals) and the much higher atmospheric values 

 (Campana and Jones, 1998). The reasons for the erratic 

 4 14 C values remain unknown, but Campana and Jones 

 speculated that the estuarine dependency of the spe- 

 cies produced the variable activities of radiocarbon in 

 individual fish for a given YOB. This was not the case 

 with gray snapper, also a species that uses the shallow 

 estuarine environment during the first years of its life. 

 Because gray snapper is estuarine dependent, we fully 

 expected the gray snapper radiocarbon values to be 

 erratic and much higher than the reference corals. In 

 contrast, gray snapper radiocarbon values were strik- 

 ingly similar to, if not less than, red snapper and the 

 reference coral radiocarbon values at all comparable 

 YOBs (Fig. 3). Contrary to the opinions expressed by 

 Campana and Jones (1998), our limited data suggested 

 that estuarine dependency may have no effect on ob- 

 served radiocarbon values, at least for gray snapper. 



Although opaque zones are distinct in gray snapper 

 otolith cross sections, the small size and apparent lon- 

 gevity of the species pose some challenges for age inter- 

 pretation. In older fish, opaque zones are formed more 

 closely together in the otolith, making accurate counts 

 and accurate interpretation of the otolith margin more 

 difficult. We observed considerable variability in the lo- 

 cation of the first opaque zone in gray snapper; the first 

 annulus was variously located somewhat distant from 

 the core to close to and continuous with the otolith core 

 (Fig. 2, A and B). Wilson and Nieland (2001) noted the 

 same pattern in red snapper otoliths suggesting that 

 this variability may be a function of the protracted red 

 snapper spawning season, which is similar to that of 

 gray snapper, and of the rapid growth rate during the 

 juvenile stage. This variability in first opaque zone posi- 

 tion accounted for the majority of disagreement between 

 readers in initial age estimates; there was only 76.5% 

 agreement. However, experience by both readers (AJF 

 and MSB) with red snapper otoliths produced consensus 

 of 98.8% after second readings. 



Male and female gray snapper ranged in age from 1 

 to 28 years. Younger individuals composed the major 

 portion of the fishery; 90% of the catch was aged less 

 than 15 years. Maximum ages were greater than those 

 reported in previous studies. Johnson et al. (1994) re- 



