548 



Fishery Bulletin 103(3) 



whole-sagittae increments counts, owing to the initia- 

 tion of increments from a second check, which formed 

 approximately 5 days after hatching. With whole-sag- 

 ittae increment counts, actual fish age was underesti- 

 mated by approximately 5 days. 



The coefficients of variation (CV), which indicates 

 the precision of age estimates, varied from 1.4% to 

 8.3% (Fig. 5). CVs were statistically different among 

 age estimation methods for both larvae and juveniles 

 (Kruskal-Wallis ANOVA, P<0.001). Lapilli from both 

 larvae and juveniles had lowest CVs, indicating high 

 precision. Whole sagittae and P2S transverse sections 

 for juveniles were comparable, but lower precision for 

 larvae was observed. However, if transverse sections 

 are used for aging, the preparation of both sides is 

 important in the case of larvae (with regard to preci- 

 sion; see Fig. 5) and mandatory in the case of juveniles 

 (with regard to accuracy; see Fig. 4B). In addition, the 

 confidence of the otolith reader in increment recognition 

 (Fig. 5) indicated that the most clear and easy to count 

 increments were found in the lapilli. 



Discussion 



First-increment formation 



In prior studies, the age of larval and juvenile spot was 

 estimated by adding five days to the number of incre- 

 ments counted from sagittae (e.g., Warlen and Chester, 

 1985; Flores-Coto and Warlen, 1993; Ross, 2003). Our 

 research indicated that increment formation in sagit- 

 tae occurred at hatching. The only study validating 

 first-increment formation in spot used linear regres- 

 sion analysis for laboratory-reared fish (Peters et al. 1 ). 

 The intercept of their regression line (age in relation to 

 number of increments) indicated that the first increment 



Peters, D. S, Jr, J. C. DeVane, M. T. Boyd, L. C. Clements, 

 and A. B. Powell. 1978. Preliminary observations on feed- 

 ing, growth and energy budget of larval spot iLeiostomus 

 xanthurus). In Ann. Rep. Southeast Fish. Cent., Beaufort 

 Lab. to U.S. Dep. Energy, p. 377-397. Beaufort Laboratory, 

 National Marine Fisheries Service, Beaufort, NC. 



