Pilling et al,: Validation of annual growth increments in the otoliths of Lethnnus mahsena and Apnon wrescens 609 



100%-, 



§,80% 



-D 

 0) 



5 60%. 



159 



144 152 44 34 113 



Jan ' Feb ' Mar ' Apr May Jun Jul Aug Sep ' Oct ' Nov ' Dec 



Month 



Figure 10 



Proportion of A. virescens otoliths with stained edge on the growing tip of 

 the dorsal lobe, by month. Numbers denote sample size. 



Jan/Feb Mar/Api May/Jun Jul/Aug Sep/OcI No\/Dec 



Months 



Figure 11 



Marginal increment plot by month for P. filamentosus. Marginal 

 increment measured in VID units (pi.xels). Data segregated as 

 in Table 1. Error bars denote one standard error. 



are derived through length-based methods, which for long- 

 hved, slow growing species are considered uncertain. The 

 preliminary back-calculated growth parameters from our 

 study are the first otolith-based estimates of growth for 

 the study species at these particular locations. Although 

 these estimates are not definitive, they do suggest that 

 current length-based growth estimates for A. virescens 

 may have overestimated mean growth rate and asymptotic 

 length. For L. mahsena, growth rate may have been under- 

 estimated, and asymptotic length overestimated. However, 

 by constraining the value of L^ to levels in keeping with 

 the maximum size found in length distributions from the 

 region (52 cm), we obtained a similar growth rate to that 

 identified by Bautil and Samboo (1988). If snappers do 

 indeed have a longer life span than that indicated by 

 length-based assessments, they may be more vulnerable 



to overfishing than previously thought. Future work will 

 involve the estimation of more definitive growth param- 

 eters based on length-at-age data derived from otoliths. 



Acknowledgments 



The authors wish to thank the Directors and staff of 

 CEFAS, Albion Fisheries Research Centre and the Sey- 

 chelles Fishing Authority who collaborated on this project 

 and provided the data necessary for this analysis. Three 

 anonymous reviewers are thanked for their helpful com- 

 ments on the manuscript. The project to which this paper 

 relates was funded by the Department for International 

 Development of the UK through the Fisheries Manage- 

 ment Science Programme. 



