Echave et al Interdecadal change in growth of Anoplopoma fimbria in the northeast Pacific Ocean 
365 
Table 1 
Growth parameters (L^average maximum length, n=mean growth coefficient, f 0 =mean theoretical age a fish would have been 
at zero length! for male sablefish (Anoplopoma fimbria) in Alaska estimated with data from the annual longline survey conducted 
cooperatively by the Fisheries Agency of'Japan and the Alaska Fisheries Science Center of the National Marine Fisheries Service 
in 1981-93 and by the Alaska Fisheries Science Center during 1996-2004. Estimates were made for 6 management regions 
with the von Bertalanffy model fitted to age-length data stratified by region and survey period, where n is the number of age- 
length observations and an asterisk (*) indicates a significant difference between the 2 periods, 1981-93 and 1996-2004, in that 
particular region. The 6 regions are the Chirikof, Kodiak, Shumagin, and Southeast, all in the Gulf of Alaska, and the eastern 
Bering Sea and Aleutian Islands. Standard errors of the mean (SE) are provided in parentheses. RSS = residual sum of squares. 
Region 
Survey period 
k 
U 
RSS 
n 
All regions combined 
1981-93 
64.6 (0.38) 
0.287 (0.03) 
-2.07 (0.60) 
3644 
3429 
1996-2004* 
67.7 (0.16) 
0.292 (0.01) 
-2.25 (0.21) 
904 
2614 
1981-2004 
66.2 (0.28) 
0.30 (0.03) 
-2.19 (0.51) 
18,954 
6043 
Chirikof 
1981-93 
70.2 (1.02) 
0.239 (0.03) 
-2.288 (0.70) 
448 
128 
1996-2004* 
67.3* (0.48) 
0.335 (0.06) 
-1.617 (1.02) 
487 
294 
1981-2004 
67.8 (0.45) 
0.327 (0.03) 
-1.287 (0.48) 
1230 
422 
Aleutian 
1981-93 
67.0 (0.55) 
0.195 (0.03) 
1329 
726 
1996-2004 
68.1 (0.48) 
0.243 (0.02) 
-2.898 (0.59) 
478 
543 
1981-2004 
67.0 (0.55) 
0.195 (0.03) 
-5.101 (1.23) 
2235 
1269 
Kodiak 
1981-93 
65.1 (0.66) 
0.352 (0.06) 
-1.685 (0.79) 
1737 
598 
1996-2004* 
66.6 (0.34) 
0.357 (0.07) 
-2.052 (1.21) 
606 
542 
1981-2004 
66.0 (0.39) 
0.365 (0.04) 
-1.423 (0.55) 
3239 
1140 
Shumagin 
1981-1993 
64.3 (0.50) 
0.440 (0.07) 
-0.793 (0.60) 
1625 
684 
1996-2004* 
70.1 (0.98) 
0.193 (0.03) 
-4.501 (1.08) 
438 
267 
1981-004 
65.3 (0.49) 
0.352 (0.05) 
-1.669 (0.63) 
2914 
951 
Bering 
1981-1993 
64.9 (0.64) 
0.197 (0.04) 
-6.264 (1.67) 
1154 
757 
1996-2004* 
69.3* (0.50) 
0.237 (0.03) 
-3.48 (0.86) 
600 
363 
1981-2004 
66.7 (0.71) 
0.186 (0.03) 
-6.250 (1.69) 
4695 
1120 
Southeast 
1981-1993 
67.0 (0.79) 
0.219 (0.04) 
-3.827 (1.19) 
1998 
536 
1996-2004* 
68.3 (0.37) 
0.307 (0.04) 
-1.714 (0.73) 
829 
605 
1981-2004 
67.7 (0.45) 
0.271 (0.03) 
-2.384 (0.65) 
4136 
1141 
time series. If the conversion matrices and the weight- 
at-age vector are developed with growth data that do 
not correspond with the true underlying growth, they 
can bias the stock assessment (Hanselman et al., 2007). 
Using the updated growth curves from the 2 survey 
periods reported in this study, we created new length- 
age conversion matrices and a new weight-at-age vector 
and applied them to the current stock assessment model 
(Hanselman et al., 2007). 
Results 
Length-at-age analysis 
Our results indicate that previously used growth esti- 
mates in the stock assessments of sablefish in Alaska 
(assessments before 2007) obtained from length-strat- 
ified sampling were erroneously too large. A compari- 
son of growth estimates from 1981-93 data updated to 
correct for this bias with estimates from more recent 
data (1996-2004) indicates that sablefish are growing 
to a larger maximum size in more recent years. The 
estimates of average maximum length (L m ) used in the 
stock assessment of Alaskan sablefish in 2007 (Sasaki’s 
[1985] estimate from length-stratified data) were 69 cm 
FL for males and 83 cm FL for females (Hanselman et 
al., 2006). Maximum lengths were smaller in our bias- 
corrected estimates for the same time period (1981-93; 
Tables 1, 2) than in the 2007 stock assessment model: 
males = 64.6 cm FL, females=75 cm FL. Our estimates 
for the more recent period (1996-2004; Tables 1, 2) are 
significantly larger (males = 67.7 cm FL, females=80.1 cm 
FL) than the bias-corrected estimates from the earlier 
period, but these estimates for the recent period are still 
smaller than the estimated lengths incorrectly used in 
earlier stock assessments. 
The growth rates of male and female sablefish in 
Alaska differed significantly across areas and survey 
periods (P<0.05; Tables 3, 4). In the data from the 
earlier period, both male and female sablefish display 
smaller asymptotic lengths (LJt and younger ages t 0 
than do sablefish in data from the more recent time 
period (Fig. 2). Significant differences were detected 
between the 2 male growth curves (P<0.001; Table 1). 
Test results on the female data showed that the L 
