Rodgveller et al.: Age at maturity, skipped spawning, and fecundity of female Anoplopoma fimbria 
95 
Age (yr) 
Figure 3 
Proportion of mature female sablefish ( Anoplopoma fimbria) by age 
that would skip spawning on the continental shelf in the central 
Gulf of Alaska in December 2011. Immature fish are not included. 
The great majority of fish that would skip spawning were found on 
the shelf. The correlation coefficient (r) with its associated P-value 
is also provided. 
more similar to the proportion in the annual summer 
longline surveys, when fish that would skip spawning 
were classified as mature, than when they were classi- 
fied as immature (Fig. 5 A). When fish that would skip 
spawning were classified as mature (Fig. 5 A, black 
line), the annual estimates of maturity from the sum- 
mer longline surveys were similar to the estimates 
from the winter survey at moderate ages (Fig. 5 A). 
At younger ages, the annual estimates of the propor- 
tion of mature fish from summer surveys were higher 
than the estimates from the winter survey; conversely, 
at older ages, the proportion of mature fish was lower 
in estimates from the summer survey. When fish that 
would skip spawning were classified as immature in 
the winter survey (Fig. 5 A, gray line), the estimated 
proportions of mature fish at each age from the sum- 
mer surveys were discernibly higher in all years (Fig. 
5 A). 
The logistic curve fitted to samples taken during the 
summer of 2011, the year in which the winter survey 
occurred, was intermediate between the curves from 
the winter where fish that would skip spawning were 
classified as mature and the curve where fish that 
would skip spawning were classified as immature, and 
the fit was dissimilar to both, especially at moderate 
ages (Fig. 5 B, Table 2 ). The 050% was 6.8 years in the 
winter when fish that would skip spawning were classi- 
fied as mature, 8.0 years for samples collect- 
ed during the summer, and 9.9 years in the 
winter when fish that would skip spawning 
were classified as immature. Unlike the ma- 
jority of curves based on data from the an- 
nual summer longline surveys, estimates of 
the proportion of mature fish in the summer 
of 2011 were very similar to those from the 
winter at young ages (Fig. 5 B). The differ- 
ence in the curves based on data from the 
winter and summer surveys conducted in 
2011 can be attributed more to a difference 
in 050% than to a difference in slope. 
The estimates of maturity at age current- 
ly used in the stock assessment for sablefish 
in Alaska, determined from samples taken 
during the summer in the early 1980 s, were 
higher than the estimates from the winter 
survey at younger ages (6 years), when fish 
that would skip spawning were classified as 
mature (Fig. 50 , but were similar at older 
ages. The pooled maturity at age for fish 
captured during the summer longline sur- 
veys (from 1996 to 2012 ) was also higher at 
younger ages, but it was lower at older ages 
(Fig. 50 . This pattern can be attributed 
primarily to differing slopes (Table 2 ). This 
trend is the same one that was apparent in 
the majority of curves fitted to data from 
the annual summer longline surveys (Fig. 
5 A). The age-at-maturity values currently 
used in the stock assessment of sablefish in 
Alaska and the mean age at maturity from 
the annual summer longline surveys were much higher 
than the values from the winter survey, when fish that 
would skip spawning were classified as immature (Fig. 
50 . 
Biomass and target-fishing reference points 
The estimates of SSB were similar when the Alaska 
sablefish population model was run with the matu- 
rity curve fitted to data from the winter survey con- 
ducted in 2011 (when fish that would skip spawning 
were classified as mature), the mean age at maturity 
across all summer longline surveys, or the maturity 
curve currently used in stock assessment (base mod- 
el) (Fig. 5 ). Estimates of SSB were lower when ma- 
turity data were used from the summer longline sur- 
vey conducted in 2011, and lowest when data were 
used from the winter survey conducted in 2011 and 
fish that would skip spawning were classified as im- 
mature (Fig. 6). Compared with the base model, the 
maturity curves based on data from winter and sum- 
mer 2011 caused larger dips in SSB in years when 
model projections included large recruitment. The 
dips in SSB occurred because these maturity curves 
had lower estimates for the proportion of mature fish 
at young ages, and such low proportions translate to 
fewer mature fish when there are more young fish 
