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Fishery Bulletin 108(1) 
Figure 1 
Locations in the central Gulf of Alaska where female dusky rockfish ( Sebastes variabilis ) samples were 
collected in 2000 and 2001 for the growth and maturity study. Number of samples collected within 
each Alaska Department of Fish and Game statistical area, delineated by shaded blocks, are reported 
in each block. 
Von Bertalanffy growth parameters for dusky rock- 
fish in the central Gulf of Alaska were compared to 
the growth parameters derived from data collected for 
the maturity study (above). A larger set of age-length 
data, randomly collected from the 1996 to 2003 NMFS 
Gulf of Alaska groundfish surveys (GOAS), was used 
for male and female dusky rockfish separately and for 
combined sexes if no difference was found. A growth 
function was fitted to the data to test for significant dif- 
ferences in growth rate between the males and females 
and the combined-sex age-length data. Differences be- 
tween sexes in the von Bertalanffy growth parameters 
were tested with a likelihood ratio test (Kimura, 1980; 
Haddon, 2001). This test was also used to determine 
whether growth parameters of female dusky rockfish 
caught in the NMFS GOAS were different from those 
values calculated from the maturity study collection. 
An allometric weight-length function expressed as 
W = aL b , where W is weight in grams, and L is length 
in millimeters, was fitted to the weight and length 
data from the maturity samples collected in 2000-01, 
and the NMFS GOAS data from 1996 to 2003. Values 
for constants a and b were estimated by linear regres- 
sion of logarithmically transformed weight-length data 
A gonadosomatic index (I G ) was calculated with the 
formula 
[/G = 100 (gonad weight (g)/ total body weight (g))], (1) 
to show seasonal changes in development of the ovary 
with respect to the total body weight. Gonad weights 
were not collected in May of 2001. 
Growth parameters for the female dusky rockfish col- 
lected in the Gulf of Alaska for the maturity estimates 
were calculated by using nonlinear least squares to fit 
the von Bertalanffy growth equation to age-length data. 
The von Bertalanffy equation can be expressed as 
L t = L„{l _ e ( -&*d-fo) (2) 
where L t = the predicted length (mm FL) at age t 
(years); 
L 0O = the mean asymptotic length (mm) at maxi- 
mum age; 
k = the growth constant (per year); and 
t 0 = the age (years) at which the fish would have 
been zero length. 
