McGovern et al.: Changes in the sex ratio and size at maturity of Mycteroperca microlepis 
805 
in March and April along the southeast Atlantic coast. 
Hood and Schlieder ( 1992 ) and Coleman et al. ( 1996 ) 
indicated that peak spawning occurred during Feb- 
ruary and March in the Gulf of Mexico. 
Despite the large number of specimens examined 
during 1994-95 (n=3879), transitional specimens 
(n= 39) made up a small percentage (1.0%) of indi- 
viduals collected. The low number of individuals with 
transitional gonads may have been due to the rapid 
nature of sex transition that appears to occur imme- 
diately after the spawning season. Smith (1965) and 
Moe ( 1969) suggested that other groupers may have 
a quick rate of sex transition. Because there was no 
significant monthly difference in the mean length of 
gag between 889 and 1050 mm TL landed during 
January through July, we feel that the peak in the 
number of transitional specimens during April and 
May was real and not an artifact of the emergency 
rule that required fishermen to land only larger fish 
(>889 mm TL) after 18 April. Coleman et al. (1996) 
stated that sex transition in gag and other grouper 
species may be socially mediated either through size 
ratio or sex ratio cues. Shapiro et al. (1993b) pro- 
posed that one function of annual spawning aggre- 
gations in red hind may be that of enabling a female 
to determine if it should function as a female or a male 
during the next spawning season. Shapiro et al. ( 1993b) 
further suggested that if this hypothesis is true, sex- 
changing individuals should be found soon after the 
aggregation has dispersed. The high percentage of 
males and transitionals taken during April and May 
in this study indicates that aggregations may remain 
intact for a short time after the spawning season. 
Van Sant et al. ( 1994) and MARMAP tagging data 1 
provided evidence that some gag migrate from off- 
1 1998. Unpublished data from MARMAP tagging study. Marine 
Resources Research Institute, Charleston, SC. 
