736 
Fishery Bulletin 96(4), 1998 
grouper life history in South Florida waters, but their 
study was limited because most of the fish examined 
were eviscerated and could not be sexed. Conse- 
quently, they could not describe sex-specific growth 
rates, length and age at sexual maturity, length and 
age at sexual transition, or sex ratios. Furthermore, 
black grouper often attain much larger sizes than 
the largest fish aged by Manooch and Mason, who 
acknowledged that black grouper can probably live 
longer than the oldest fish they aged (14 years). 
Garcia-Cagide and Garcia (1996) estimated the 
length at sexual maturity, the length at transition 
from female to male, and described seasonal spawn- 
ing patterns of black grouper captured off Cuba, but 
they did not estimate ages of the fish they examined. 
Additional information on growth, maturation, and the 
length and age at transition are needed to fully assess 
the status of black grouper stocks. Our article describes 
growth, length and age at maturity, length and age at 
sexual transition, dichromatism between the sexes, and 
seasonal patterns of gonad development. In addition, 
we used marginal-increment analysis to validate the 
ages of young black grouper. 
Methods 
Collections 
We obtained black grouper from a variety of sources 
throughout the Florida Keys and Florida’s Gulf coast 
from November 1994 to November 1996. Most of the 
black grouper in our sample were caught by spear 
fishermen and landed in the Florida Keys (n = 733). 
Commercial hook-and-line and bottom longline black 
grouper catches were landed and sampled at fish 
houses in Pinellas County on Florida’s Gulf coast 
( /2 =433 ). Commercial fishermen captured grouper 
primarily south of 25°N in depths greater than 37 m, 
but some catches were made north of 25°N along the 
Florida Gulf coast to the Florida Panhandle in depths 
of 37-100 m. Most of the black grouper landed in 
Pinellas County were caught on or near the Tortugas 
Banks west of the Florida Keys by commercial 
longline fishermen, whose operations are restricted 
by federal regulations to depths greater than 20 fath- 
oms (37 m). 
Standard length (SL), fork length (FL), and total 
length (TL) were measured to the nearest millime- 
ter (mm). Total length was measured following Hubbs 
and Lagler ( 1964). Fork length was measured as the 
center-line length from the tip of the lower jaw to 
the center of the caudal fin. Unless otherwise indi- 
cated, all lengths reported are total lengths. Large 
grouper were weighed to the nearest 50 grams and 
smaller grouper were weighed to the nearest gram. 
Otoliths (sagittae) were removed, rinsed in water, 
and stored dry until sectioned. Otoliths were weighed 
to the nearest 0.01 mg. Gonad weight (g) was re- 
corded, and gonad samples for histology were re- 
moved from the fish and preserved in 10% buffered 
formalin; they were later soaked in water for one hour 
and then stored in 70% ethanol. 
We examined most grouper to detect color changes 
that might be associated with the sex of the fish. All 
of the fish we examined were dead and had been on 
ice for several hours to a week. The colors of the pec- 
toral, anal, dorsal, and caudal fins were recorded 
throughout the year during routine sampling of go- 
nads and otoliths. Only grouper for which we had 
gonad histology samples were selected for differen- 
tial color analysis. 
Age and growth 
The left sagitta was usually used for age estimation; 
however, in cases where the left otolith was broken, 
lost, or damaged during processing, the right otolith 
was substituted. We prepared most otoliths by using 
a Buehler Isomet low-speed saw with a diamond 
blade to cut three or four thin sections to a thickness 
of approximately 0.5 mm, one of which was through 
the otolith core. Sections were then mounted on a 
microscope slide with Histomount. Initially, we pre- 
pared some otoliths for age estimation by embedding 
them in Spurr, a high-density plastic medium (Secor 
et al., 1992). A 1- to 2-mm-thick transverse section 
containing the otolith core was cut. The section was 
mounted on a microscope slide with thermoplastic 
glue (CrystalBond 509 adhesive) and polished with 
“wet/dry” sandpaper (grit sizes ranging from 220 to 
2,000) until annuli were visible. Sections were then 
polished on a Buehler polishing cloth with 0.05-p 
gamma alumina powder to remove scratches. There 
was no consistent difference in the quality of either 
preparation technique. Mounting the sections in 
Histomount took less time than embedding them in 
Spurr, so we adopted it as our standard protocol. 
Annuli were counted using compound microscopes 
equipped with transmitted light and dissection mi- 
croscopes equipped with reflected light. Two inde- 
pendent readers counted annuli on each otolith sec- 
tion three times each, for a total of six counts for 
each otolith. Thirty-two otoliths were considered 
unreadable by one or both readers and were dis- 
carded from our analysis before the completion of six 
readings. Annulus counts for individual otoliths of- 
ten varied among readings. We established criteria 
for accepting or rejecting individual otoliths by cal- 
culating a coefficient of variation: 
