88 
Fishery Bulletin 106(1 ) 
TabSe 3 
Length at 50% maturity for male and female dolphinfish ( Coryphaena hippurus). Lengths were estimated by fitting a logistic 
model (see text) with nonlinear regression analysis. The standard errors (SE) of each parameter are shown in parentheses. 
n = sample size, Q = model parameter, L 50 = fork length (mm) at 50% maturity, and Cl = 95% confidence interval for L 50 
Sex n Q(SE) L 50 (SE) Cl 
Males 74 0.05(0.02) 476.13(6.24) 460.9-494.7 
Females 154 0.08(0.02) 457.58(2.54) 453.1-462.5 
The highest median GSI values occurred in May for 
both male (Fig. 4A) and female (Fig. 4B) dolphinfish; 
however, these values were not corrected for differences 
in body size. Length-adjusted mean gonad weights were 
significantly different by month (ANCOVA: P<0.001) for 
both male and female dolphinfish (Fig. 4C). Length- 
adjusted mean gonad weights were highest in the late 
spring and summer and then decreased from midsum- 
mer into the fall. Gonad weights from November to 
February were not included because of the low sample 
size (n = 9). September gonad weights were significantly 
lower than May and June gonad weights in males (Fig. 
4C); all other male comparisons were nonsignificant. 
There were significant differences in the length-adjusted 
gonad weights of females between almost every month, 
but most differences were found for October, when go- 
nad weights were significantly lower than in May, June, 
July, and August (P<0.001 for all) (Fig. 4C). 
For both 2002 and 2003, hatching dates of dolphin- 
fish occurred for all months, but the bulk occurred 
from January to June (Fig. 5). In 2002, the majority of 
age-0 dolphinfish sampled (83%) had back-calculated 
hatching dates in the months of January through June. 
Similarly, in 2003, 76% of age-0 dolphinfish had back- 
calculated hatching dates for this same period. 
Discussion 
Age and growth 
This study is the first to use transverse cross-sections of 
sagittal otoliths to determine daily ages of dolphinfish; 
whole otoliths (Oxenford and Hunte, 1983; Uchiyama 
et al., 1986; Rivera and Appledoorn, 2000) or exposed 
sagittal planes (Massuti et al., 1999; Morales-Nin et al., 
1999) were used in prior studies. Our estimated birth 
dates are in good agreement with known spawning 
dates (Beardsley, 1967; this study); a similar indepen- 
dent comparison indirectly validated daily age data for 
dolphinfish in the Mediterranean Sea (Massuti et al., 
1999; Morales-Nin et al., 1999). Future work is needed to 
compare the multiple techniques that have 
been used to prepare age-0 dolphinfish oto- 
liths in order to determine which technique 
is most efficient. 
The daily growth rates for dolphinfish 
are faster than those of many species, but 
are a common characteristic of pelagic pi- 
scivores (Brothers et al., 1983; La Mesa et 
al., 2005). Our estimate of daily growth 
rate (3.78 mm FL/day) is similar to that of 
550-1325 mm FL dolphinfish from Puerto 
Rico (3.59 mm/day; Rivera and Appledoorn, 
2000) and 200-600 mm FL dolphinfish 
from the western Mediterranean Sea (~3.50 
mm/day; Massuti et al., 1999). In Barba- 
dos, the average growth rate of dolphin- 
fish of 174-1100 mm SL is estimated at 
4.71 mm standard length per day (Oxenford 
and Hunte, 1983). Based on daily growth 
increments in sagittal otoliths of dolphin- 
fish from the Gulf of Mexico, average first- 
year growth rate is 4.15 mm FL/day for 
fish in the size range of 250-1200 mm SL 
(Bentivoglio, 1988). 
Annual marks are not detectable on 
sagittal otoliths of >age-0 dolphinfish with 
0 1 2 3 4 5 
Age (years) 
Figure 3 
Calculated von Bertalanffy growth functions (VBGFs) for dolphinfish 
( Coryphaena hippurus) from various locations in the North Atlantic. 
GOM = Gulf of Mexico, FL = Florida, NC = North Carolina. 
