Clardy et al Life history of Menticirrhus americanus and other sciaenids 
183 
Female GSI increased from February to April, re- 
mained relatively high from May to August, and de- 
creased thereafter (Fig. 5A). Female GSI among months 
was significantly different (ANOVA: F \ o 423=32.49; 
PcO.OOOl) with values for March-September signifi- 
cantly higher than those for all other months (GH, 
Pc0.05), indicating Southern Kingfish may spawn in 
the northcentral GOM from March to September. Male 
GSI mirrored that of females (Fig. 5A) and was signifi- 
cantly different among months (ANOVA: F 10, 74 = 7 - 65 ; 
PcO.OOOl), peaking in April and reaching the lowest 
values in November (Sidak; P<0.05). 
Histological analysis confirmed the Southern King- 
fish spawning season that had been indicated by GSI 
value in our analysis. The majority of the females 
were in the early developing subphase in February; 
this percentage decreased in March as fish moved into 
the developing phase (Table 3). Females were first 
observed in the spawning capable phase (Fig. 5B) in 
March, although no POFs were seen in March. From 
April to August, >78% of captured females were in the 
spawning-capable phase; this percentage decreased to 
59% by September (Table 3). Females in the actively 
spawning subphase were found from April to Septem- 
ber (Table 3). Although some females were found in 
the spawning-capable phase in October (13%), the ma- 
jority of fish were in the regressing and regenerating 
phases, signaling the end of the reproductive season. 
By November, all females were reproductively inactive 
(Table 3). Therefore, on the basis of histological obser- 
vations, the spawning season for Southern Kingfish in 
the northcentral GOM appears to be April-September. 
Furthermore, the asynchronous oocyte development ob- 
served in females in the spawning-capable phase (Figs. 
5B and 6) indicates that Southern Kingfish is a batch- 
spawning species in the northcentral GOM. 
Seasonal spawning frequencies were estimated with 
both the POF and OM calculation methods, and they 
were calculated only for months when actively spawn- 
ing females were observed (Table 4). Results were 
similar between methods for the early and mid-season 
spawning frequencies but differed during the late sea- 
son. There was a significant difference seasonally for 
frequencies calculated with the POF method <x 2 = 17.50, 
df=2, PcO.OOOl) but not for values estimated with the 
OM method (% 2 =3.251, df=2, P>0.05). Both methods 
revealed a spawning frequency of 11.3 days between 
spawns for the early season (April-May). During the 
mid-season (June-July), spawning frequency ranged 
from 3.5 to 5.8 days between spawnings depending on 
the method. Spawning frequency in the late season (Au- 
gust-September) was much greater for the OM method 
(5.4 days) compared with the POF method (19.7 days). 
The mean annual spawning frequency was calculated 
for both methods at 6.9 days between spawnings (Table 
4). Therefore, over the course of the entire spawning 
season (April-September), Southern Kingfish spawn on 
average once every 7 days and an individual has the 
potential to spawn 26 times. 
Batch fecundity estimates were compared for 11 fe- 
males that were in the actively spawning subphase. A 
distinct group of oocytes >350 pm was observed in ac- 
tively spawning fish; therefore, oocytes >350 pm were 
considered to be undergoing OM (Fig. 6) and were 
counted for fecundity analysis. Overall BF ranged 
from 17,338 to 80,495 eggs and had a mean of 35,571 
eggs (SE 6405) (Table 5). There were no significant re- 
lationships between log 10 BF and logio TL (P 2 =0.199, 
Pi g = 2.23, P=0.169) or logio BF and logio OFBW 
