Echave et al Interdecadal change in growth of Anoplopoma fimbria in the northeast Pacific Ocean 
367 
Table 4 
Comparison of 4 age-length models used for analyses of regional and temporal effects on growth of female sablefish (Anoplo- 
poma fimbria) in Alaska. The most reasonable model, indicated with an asterisk (*), is the reduced model with a residual sum of 
squares (RSS) not significantly greater than the RSS for the full model. n = the number of observations, and x 1 = the chi-squared 
value. 
Model 
RSS 
£ 
P 
No. of parameters 
n 
Data split by each combination of region and survey period * 
24,271 
36 
Data split into 2 survey periods 
48,717 
238.9 
<0.001 
6 
Data split into 6 regions 
39,656 
168.4 
<0.001 
18 
All data pooled 
68,900 
357.9 
<0.001 
3 
8281 
lengths ranged from 68.3 to 78.3 cm FL during 
the earlier survey period, with the lowest maxi- 
mum lengths occurring in the EBS region and 
highest lengths in the Southeast. In the more re- 
cent period, asymptotic lengths were much larger, 
ranging from 76.4 cm (EBS) to 81.6 cm FL (Shu- 
magin region). During the earlier time period, 
compared to the more recent one, AI, Kodiak, and 
Southeast females grew slower and Shumagin, 
Chirikof, and EBS females displayed the opposite 
pattern. 
Several tests for differences in growth between 
pairs of regions were significant (P<0.05) for both 
sexes. Male sablefish showed fewer differences 
in growth between regions, with Chirikof males 
differing significantly from Shumagin (P=0.02), 
AI (P=0.01) and EBS (P= 0.01) males, and EBS 
males differing significantly from males in the 
Southeast (P=0.04). For female sablefish, most 
regional comparisons were highly significant, with 
the exception of the difference between AI and 
Shumagin (P=0.55), Chirikof and Kodiak (P=0.12) 
and Southeast (P=0.12), and Kodiak and South- 
east (P- 0.37). 
A consistent pattern of smaller estimates of 
t 0 , the theoretical age at zero length, was seen 
for both male and female sablefish in the earlier 
survey period, than estimates for the more recent 
survey period. These smaller values could be a 
result of small sample sizes of fish <4 years old in 
the older data sets (Sigler et ah, 1997). 
Weight-at-age 
The age-weight relationship differed significantly 
among regions in both males (P<0.001, Table 5) 
and females (PcO.OOl, Table 6). Maximum weights 
for male (Table 7) and female (Table 8) sablefish in 
all regions combined were smaller than the values 
used in the current stock assessment model, likely 
because of differences in age at length. Female 
sablefish in pooled regions reached a higher aver- 
age maximum weight-at-age than did male sable- 
fish, 5.5 kg versus 3.2 kg, respectively. 
A 
Figure 2 
Comparison of (A) male and (B) female sablefish (Anoplopoma 
fimbria) von Bertalanffy (VB) growth curves (for all of the 
6 management regions in Alaska combined) fitted to bias- 
corrected age-length data from 1981 through 1993 (shown as a 
dashed line) and fitted to age-length data from 1996 through 
2004 (shown as a solid line). Note the different scales on the 
y-axis of each figure. Sample sizes (n) contributing to the VB 
analysis are listed in the legends. 
