104 
Fishery Bulletin 108(1) 
the endolymphatic fluid. The carbon isotopic ratios in 
the otolith, in addition to pure kinetic effects, are con- 
trolled by only those metabolic pathways that modify 
the 5 13 C of the endolymphatic fluid (Radtke, 1996). Diet 
has a pronounced and significant effect on carbon isoto- 
pic ratios in the otoliths. The markedly different mean 
salinity values for summer 2002 and summer 2004 
indicate differences in freshwater inflow to Florida Bay. 
These differing regimes would likely have influenced 
primary productivity in the bay, in terms of chlorophyll 
biomass and food-web structure, which could ultimately 
be recorded as differences in carbon isotopic ratios in 
juvenile fishes. Autotrophs, mangrove detritus, sea- 
grass, and particulate organic matter play a pivotal 
role as important sources of nutrition for juvenile gray 
snapper (Melville and Connolly, 2003). Different plant 
groups display different carbon isotopic ratios in their 
organic material depending on the photosynthetic path- 
way used, and carbon isotopic ratios for the otoliths 
of prey organisms act as labels that can be measured 
through to higher trophic level consumers. Recorded 
variations of carbon isotopic ratios for the otoliths may 
therefore constitute a record of the food that these gray 
snapper consumed and show potential for assessing the 
health of the Florida Bay ecosystem. 
Mulcahy (1979) found that stable carbon isotopic ra- 
tios for the otoliths of a benthopelagic fish increased 
with fish age. This increase with maturity of the fish 
was attributed to a decrease in the metabolic production 
rate of dissolved inorganic carbon. Because we exam- 
ined only juvenile and small adult fish of a relatively 
narrow size range, it is unlikely that the observed dif- 
ferences in carbon isotopic ratios were due to differences 
in age-dependent metabolism. 
Spatial separation of regions and collection sites as 
shown in this study by using isotopic analysis of oto- 
liths has the potential for establishing habitat linkages 
between adult gray snapper on offshore reefs to those in 
nursery habitats in Florida Bay and other surrounding 
areas. Results indicate that fishery managers should 
address the whole ecosystem and connectivity between 
habitats of a known species rather than site-specific 
management. Managing and protecting a particular 
species requires spatially explicit characterization of 
all habitats and processes encountered during the life 
history of a species for the design of marine protected 
areas in coastal regions (Thorrold et al., 2001). Connec- 
tivity must be taken into consideration when assessing 
management effectiveness of economically important 
reef fish species that use multiple habitats throughout 
their life. 
Acknowledgments 
We thank all within NOAA Southeast Fisheries Science 
Center, Early Life History Unit for their assistance 
collecting samples and P. Swart and A. Saied of the 
University of Miami, Rosenstiel School for Marine and 
Atmospheric Studies, for their assistance with stable 
isotope analysis. I especially thank D. Jones for doing 
the initial statistical analysis and M. Lara for improving 
this project. The constructive comments of J. Bohnsack, 
J. Lamkin, and W. Richards were helpful in revising 
this manuscript. This study was funded in part by the 
South Florida Science Program, NOAA Coral Reef Con- 
servation Program, and NOAA Educational Partnership 
Program. 
Literature cited 
Allman, R. J. and C.B. Grimes. 
2002. Temporal and spatial dynamics of spawning, settle- 
ment, and growth of Gray snapper (Lutjanus griseus) 
from the West Florida shelf as determined from otolith 
microstructures. Fish. Bull. 100:391-403. 
Anderson, M. J. 
2001. A new method for non-parametric multivariate 
analysis of variance. Austral. Ecol. 26:32-46. 
Arslan, Z., and A. J. Paulson. 
2003. Solid phase extraction for analysis of biogenic 
carbonates by electrothermal vaporization inductively 
coupled plasma mass spectrometry (ETV-ICP-MS): an 
investigation of rare earth element signatures in otolith 
microchemistry. Anal. Chim. Acta 476:1-13. 
Ashford, J., and C. Jones. 
2006. Oxygen and carbon stable isotopes in otoliths record 
spatial isolation of Patagonian toothfish ( Dissostichus 
eleginoides). Geochim. Cosmochim. Acta 71:87-94. 
Campana, S. 
1999. Chemistry and composition of fish otoliths: path- 
ways, mechanisms and applications. Mar. Ecol. Progr. 
Ser. 188:263-297. 
Dufour, E., W. P. Patterson, T. Hook, and E. S. Rutherford. 
2005. Early life history of Lake Michigan alewives ( Alosa 
pseudoharengus) inferred from intra-otolith stable iso- 
tope ratios. Can. J. Fish. Aquat. Sci. 62:2362—2370. 
Elsdon, T. S., and B. M. Gillanders. 
2002. Interactive effects of temperature and salinity 
on otolith chemistry: challenges for determining envi- 
ronmental histories of fish. Can. J. Fish. Aquat. Sci. 
59:1796-1808. 
Gao Y., S. Joner, R. Svec., and K. Weinberg. 
2004. Stable isotopic comparison in otoliths of juvenile 
sablefish, Anoplopoma fimbria, from waters off the 
Washington and Oregon coast. Fish. Res. 68(1-3): 
351-360. 
Gauldie, R. W. 
1996. Biological factors controlling the carbon isotope 
record in fish otoliths: principles and evidence. Comp. 
Biochem. Physiol. 115B(2):201-208. 
Gerard, T. 
2007. The use of otolith microchemistry to monitor and 
evaluate the movement of coral reef fish in Southern 
Florida waters. Ph.D. diss., 74 p. A&M Univ., Tal- 
lahassee, FL. 
Huxham, M., E. Kimani, J. Newton, and J. Augley. 
2007. Stable isotope records from otoliths as tracers of 
fish migration in a mangrove system. J. Fish Biol. 
70:1554-1567. 
Kelble, C. R„ E. M. Johns, W. K. Nuttle, T. N. Lee, R. H. Smith, 
and P. B. Ortner. 
2007. Salinity patterns of Florida Bay. Estuar. Coast. 
Shelf Sci. 71:318-334. 
