Clardy et al. : Life history of Menticirrhus americanus and other sciaemds 
181 
in modified Gilson’s fluid (Bagenal, 1966) for a mini- 
mum of 3 months. Once oocytes were separated from 
ovarian tissue, they were suspended in water and all 
hydrated or OM oocytes occurring in six 1-mL aliquots 
were counted. Graphs of oocyte size-frequency distribu- 
tions of spawning-capable and actively spawning fish 
were developed to identify and determine the size of 
OM oocytes used for counts. Batch fecundity (number 
of eggs) and relative batch fecundity (RBF; number 
of eggs per gram of ovary-free body weight leggs g _1 
OFBW]) were calculated by the volumetric method (Ba- 
genal and Braum, 1971). All values for BF and RBF 
provided here are reported as a mean ± standard error 
of the mean ( SE). 
Comparison of sciaenid life histories 
Life-history data were summarized for recreationally 
and commercially important sciaenid species com- 
monly occurring in the U.S. EEZ. Species that occur 
infrequently in U.S. catches, have their centers of dis- 
tribution outside U.S. waters, or that are important 
only in the aquarium trade, were excluded from the 
comparison. In addition, commercially or recreationally 
important species for which there is little life-history 
information were excluded from the data summary. To 
treat geographically separated populations of the same 
species individually, we recognized GOM, Pacific, and 
Atlantic populations within species. Data for each of 
these species were obtained from the literature, with 
the exception of Southern Kingfish, which is described 
in this study. We summarized 8 somatic and reproduc- 
tive traits for each species: 1 ) maximum age (years), 2 ) 
maximum TL (millimeters), 3) spawning-season dura- 
tion (months), 4) spawning frequency (days), 5) RBF 
(eggs g _1 OFBW), 6 ) age at maturity (years), 7) TL at 
maturity (millimeters), and 8 ) the parameter b (mor- 
phology index: exponent of weight at length from the 
power function) in the 2 -parameter power function 
used to describe weight at length (W=aTL b ). 
Data analyses 
Somatic patterns of Southern Kingfish were quantified 
with linear and nonlinear relationships. The mean TL 
at 50% maturity (TL 50 ) was estimated with a 2-param- 
eter logistic model: 
M ' rL = l + e -r(,TL-TL 50 ) ’ (2) 
where female maturity was coded binomially as imma- 
ture ( 0 ) or mature ( 1 ). 
The relationship between sex-specific SL and TL 
was estimated with a linear model: 
SL = /3 0 +P l xTL. (3) 
We used a 2-parameter von Bertalanffy growth func- 
tion (VBGF) to describe length at age: 
TL t = TLJl-e kt ), (4) 
where TL t = TL of a fish with age t: 
The VBGF model parameters were TL„ (the mean 
hypothetical maximum TL achieved by an individual, 
in millimeters) and the growth coefficient k (the rate 
of growth, per year). We estimated longevity as the age 
(in years) taken to reach 95% and 99% of predicted 
TL„ (Fabens, 1965; Ricker, 1979) and used a power 
function to determine mean weight at length. The 95% 
confidence intervals (Cl) of the mean model parameters 
for the VBGF, power, and logistic functions were de- 
termined by using the confint algorithm distributed in 
the stats package in the base version of the program R 
(vers. 2.15.1; R Core Team, 2012). 
The GSI values were arcsine square-root trans- 
formed before analysis and were tested for normality 
(Kolmogorov-Smirnov one-sample test) and homogene- 
ity of variance (Levene’s test). A one-way analysis of 
variance (ANOVA) tested for GSI differences among 
months by sex. If a significant F-value was observed, 
monthly values were separated with a Sidak pairwise 
test; if the data were heterogeneous, a Games-Howell 
(GH) test was used (Field, 2005). Differences in spawn- 
ing frequency among seasons (early, mid, and late) 
were tested with a chi-square test. Linear regressions 
of logiQ-transformed data were used to determine if 
there were relationships between either BF or RBF as 
the dependent variable and TL, OFBW, and age as the 
independent variables. The SPSS program (vers. 20.0; 
IBM Corp., Armonk, NY) was used, and the significance 
level was P<0.05. 
Principal components analysis (PCA) was used to 
compare and describe the multivariate somatic and 
reproductive traits of 17 geographic populations (14 
species) in the family Sciaenidae. We limited our PCA 
to those populations that had available data for 5 so- 
matic and reproductive traits. Somatic traits included 
the maximum TL and the parameter b\ reproductive 
traits included duration of spawning season, RBF, and 
age at maturity. In cases where more than one value 
was reported for a trait, the median value was used 
for the PCA. The PCA was performed by eigenvalue 
decomposition of the correlation matrix with varimax 
rotation to maximally resolve loadings, and only eigen- 
values >1.0 were used. We considered any variable 
that loaded on a component at | >0.60 | to make a sig- 
nificant contribution to interpretation of that compo- 
nent (Hair et ah, 1984). The SPSS program was used, 
and the significance level was P<0.05. 
Results 
Somatic characteristics 
From April 2008 to May 2009, 519 Southern Kingfish 
(434 females, 85 males) were sampled; no fish were col- 
lected in January 2009. Of these fish, 508 were collect- 
