Sadovy et al : Age and growth of Epinephelus guttatus in Puerto Rico and Si Thomas 



523 



Fork Length (mm) 



100 200 300 400 



Fork Length (mm) 



500 



Figure 7 



(upper) Relationship between otolith radius and fork length 

 for Epinephelus guttatus from Puerto Rico (1 micrometer 

 unit = 0.0312 mm), (lower) Relationship between un- 

 sectioned otolith width and fork length for Epinephelus 

 guttatus from Puerto Rico. 



PUERTO RICO 



4 6 8 10 



Age Group 



ST. THOMAS 



^^ Annulus I -•- Annulus II Annulus III 



-*- Annulus IV — — Annulus V 



Figure 8 



(upper) Mean back-calculated fork length of annuli I-V 

 for Epinephelus guttatus from Puerto Rico. Asterisks 

 denote significance at p<0.05; NS = nonsignificant. 

 Oower) Mean back-calculated fork length of anmoli I-V 

 for Epinephelus guttatus from St. Thomas. Asterisks 

 denote significance at p<0.05. 



in Table 4. Fork length at time of capture (i.e., observed 

 FL) did not differ significantly between the sexes for 

 age-groups 2-8 (Table 4). However, both age- and size- 

 frequency distributions from both Puerto Rico and St. 

 Thomas differed significantly by sex (age: D = 0.593, 

 p<0.01; size: D = 0.576, p<0.01) (Fig. 9). 



Females were found at ages 1-9, males at ages 2-17, 

 and individuals undergoing sexual transition at ages 

 3-7 (Table 4). No sexually-mature individuals were 

 detected below age 2 years. Fifty percent of females 

 had attained sexual maturity by age 3. 



Discussion 



Validation and formation of opaque zones 



Opaque zones incrementally deposited in the sagittae 

 of the red hind Epinephelus guttatus were validated 



as annual in this study, both by marginal increment 

 analysis and by a field study involving the marking of 

 otoliths by OTC. Although the possibility of bi- or multi- 

 annual growth lines (Deelder 1981, Lee et al. 1983) for 

 fish aged 11 years and over could not be discarded, 

 these age-groups constituted a small percentage of 

 sampled individuals; hence, the validation may be ap- 

 plied confidently to the exploited segment of red hind 

 stocks in the region. 



It is not known what causes the formation of opaque 

 and translucent zones in this species. However, since 

 zones are found in both adults and juveniles, they are 

 clearly not caused exclusively by spawning activity 

 (Nekrasov 1980). Opaque zone formation has been pro- 

 posed to be associated with low somatic growth rates, 

 and translucent zones with high growth rates, in the 

 white grunt Ha^mulon plumieri (Sadovy and Severin 

 1992). A similar relationship is proposed for the red 



