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



525 



using whole otoliths and length-frequency analyses 

 for ageing, reported L^=507mmFL in Bermuda. 

 The largest fish sampled in the present study were 

 490 mm FL in Puerto Rico and 504mmFL in St. 

 Thomas. In several years of intensive sampling of 

 thousands of red hind from local commercial landings, 

 Fisheries Research Laboratory (FRL) data recorded 

 <2% of individuals >500mmFL (FRL, unpubl. data). 

 These data reflect asymptotic lengths established in 

 the present study. Randall (1983) reported the largest 

 West Indian specimen collected to be 673mmFL, and 

 Smith (1971) reported the largest fish he examined to 

 be SlOmmSL (618mmFL using the above FL/SL 

 relationship). 



Growth parameters obtained using otoliths as the 

 ageing structure for western Atlantic species of the 

 genus Epinephelus are shown in Table 5. The data for 

 E. guttatus in Puerto Rico and St. Thomas fall within 

 the range of values of L^, K, and maximum age 

 reported for western Atlantic grouper. A maximum of 

 17 growth zones in Puerto Rico and 18 growth zones 

 in St. Thomas were recorded. We consider the esti- 

 mated longevity of 17 + and 18+ to be reasonable for 

 commercially-taken red hind in Puerto Rico and St. 

 Thomas, respectively. Luckhurst et al. (1992) recorded 

 22 ( ± 1) opaque zones in an unusually-large 720mmFL 

 individual from Bermuda. 



Lengths-at-capture were consistently higher than 

 back-calculated lengths for each age-group (Figs. 5, 6). 

 The higher observed mean fork lengths generally 

 reflect additional growrth between previous ring forma- 

 tion and time of capture. However, the notably high 

 observed mean FL of ages-1 and -2 fish for both Puerto 

 Rico and St. Thomas may be due, in part, to selection 



by the fishery of the largest fish in these younger age- 

 groups. Similar selection was also reported for the first 

 two age-classes in E. morio (Moe 1969) and may be 

 especially common in longer-lived, slower-growing 

 species, such as grouper (Bannerot 1984). When sam- 

 pling is biased towards larger individuals of young year- 

 classes, there may be artificial depression of K in the 

 VBGF (Ricker 1975). A downward bias would generally 

 produce conservative management advice in terms of 

 justifying imposition of minimum size regulations based 

 on future returns to the fishery (Bannerot 1984). 



The relationship between FL and OR for both loca- 

 tions is somewhat weaker than in other studies of fish 

 age and growth. Since the OW/FL relationships for 

 otoliths from both locations are strong, this indicates 

 that variability is introduced by the position on the sec- 

 tioned otolith selected for measurement and counting 

 of opaque zones, rather than by a poor relationship 

 between body length and otolith size (Fig. 7). 



The regressions for mean back-calculated fork 

 lengths of annuli I-V of age-groups 1-14 for Puerto 

 Rico and St. Thomas are statistically significant, with 

 two exceptions (Fig. 8). Such a trend could suggest a 

 reverse "Rosa-Lee" phenomenon, indicating enhanced 

 survivorship of fast-growing fish (Ricker 1975). If this 

 were true, it would result in an upward bias of the 

 parameter K in the VBGF. However, sample sizes for 

 individuals above age-group 10 are very low, and re- 

 gressions for age-groups 5-10 are not significant, with 

 the exception of annulus II for Puerto Rico. Since these 

 age-groups comprise the bulk of commercial landings, 

 we believe that bias to estimates of growth parameters 

 derived in the present study is negligible. Furthermore, 

 since a similar increase is apparent in most age-groups 



