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Fishery Bulletin 106(1 ) 
Table 2 
Von Bertalanffy growth parameters calculated for male, female, and combined sexes (including individuals whose sex could not 
be determined) of dolphinfish ( Coryphaena hippurus) from nonlinear regression model fits. Data are presented for (A) daily ages 
of otoliths (from dolphinfish <650 mm) along with annual ages of >age-0 dolphinfish presented as absolute ages, and (B) daily 
aged otoliths (from dolphinfish <650 mm) along with annual ages of >age-0 dolphinfish presented as relative ages, assuming a 
15 April hatching date. The standard errors of each parameter are shown in parentheses. n = sample size, L co =asymptotic length, 
£=growth coefficient, and t 0 =theoretical age at zero length. 
Method 
n 
^oo (mm) 
k (1/yr) 
*0 <yr) 
A Otoliths (<650 mm) aged daily and 
scales aged yearly (absolute ages) 
Males 
189 
1286 (29.10) 
1.33(0.12) 
-0.016(0.04) 
Females 
146 
1250 (109.60) 
1.24(0.28) 
-0.059(0.05) 
Combined sexes 
341 
1289 (25.95) 
1.27 (0.08) 
-0.026(0.02) 
B Otoliths (<650 mm) aged daily and 
scales aged yearly (in relation to a 
15 April hatching date) 
Males 
188 
1299 (30.80) 
1.12 (0.11) 
-0.089(0.05) 
Females 
145 
1237 (92.14) 
1.10(0.23) 
-0.116 (0.06) 
Combined sexes 
339 
1299 (26.31) 
1.08 (0.07) 
-0.086 (0.03) 
the fall, and stayed low during winter months (Fig. 1). 
There was a significant difference in marginal incre- 
ment width per month (ANOVA: P=<0.001) for the 
Figure 1 
Box plot of the marginal increment width (mm) for age-1 
dolphinfish ( Coryphaena hippurus) (sampled from May 2002 
through May 2004) pooled by month ( January-December). 
The 25 th percentile of the marginal increment width data is 
represented by the boundary of the box closest to zero, rela- 
tive to the y-axis, and the 75 th percentile is represented by 
the boundary of the box farthest from zero. The line within 
each box is the median value. Whiskers (error bars) above 
and below the boxes indicate the 90 th and 10 th percentiles, 
respectively. Outlying values for both upper and lower ranges 
are represented by closed circles. Sample sizes are given above 
the box for each month. 
period of March through November. Mean marginal 
increment width in May was significantly higher than 
in April (Tukey HSD: P=0.03) and October (P=0.03), 
whereas in June, it was significantly higher than 
in April (P<0.001), September (P=0.04), and Oc- 
tober (PcO.OOl). All other comparisons were non- 
significant. 
Growth rates of dolphinfish are extremely fast 
during their first year and their maximum longev- 
ity is only three years (Fig. 2A). Female dolphin- 
fish appeared to have a slower growth and shorter 
longevity than male dolphinfish; only three female 
dolphinfish reached age 2. However, there was 
no significant difference between the male and 
female von Bertalanffy growth models (likelihood 
ratio tests: x 2 =6.52, df=3, P=0.08). 
The growth model fitted the relative age data 
well (under the assumption of a biological hatching 
date of 15 April) for >age-0 dolphinfish. However, 
the sizes of age-0 dolphinfish (where age was es- 
timated by using annual marks on scales) at their 
relative age (Fig. 2B) did not show good agreement 
with size-at-age based on daily ages determined 
from otoliths. Thus, a combination of otolith-based 
daily ages for age-0 dolphinfish and scale-based 
relative ages for >age-0 dolphinfish were used 
when fitting a second von Bertalanffy growth 
model. The second von Bertalanffy growth func- 
tion showed that males grow faster and reach a 
larger maximum size than females (likelihood ra- 
tio test: x 2 =10.14, df=3, P=0.02) (Fig. 2C; Table 2). 
By using a biological hatching date, the combined 
sexes model fit was improved from an r 2 of 0.67 to 
an r 2 of 0.73. The mean length-at-age values for 
dolphinfish collected in June, July, and August 
