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Fishery Bulletin 1 14(1) 
Figure 2 
Histological preparations of thin sections of ovaries from sablefish ( Anoplopoma fimbria ) sampled in the 
central Gulf of Alaska in December 2011. (A) An ovarian section from an immature fish that has a thin 
ovarian wall and thin lamellae without blood vessels. (B) An ovarian section from a fish that will skip 
spawning and has a thicker ovarian wall, thicker lamellae that surround the oocytes, and many blood ves- 
sels. In both specimens, there are no maturing, vitellogenic oocytes. 
was the sum of the numbers of those that would skip 
spawning and fish that would spawn in the current 
season). The great majority of those that would skip 
spawning (20 out of 23, 87%) were caught on the shelf, 
specifically in troughs at stations adjacent to the slope. 
Most of the fish on the slope were mature (fish that 
would either spawn or skip spawning, 90%), but only 
4.5% of mature fish were fish that would skip spawn- 
ing (3 of 63). Only 14% of the fish on the shelf were 
mature and 43% of these mature fish (19 out of 44) 
were fish that would skip spawning. Skipped spawn- 
ing was observed in fish ranging in age from 4 to 17 
years, although sample sizes for fish (both mature and 
immature) >17 years of age were often limited to 1 or 
2 fish. There was a significant, positive correlation be- 
tween age and the proportion of mature fish that would 
skip spawning on the shelf, where the great majority 
of those that would skip spawning were found (Fig. 3). 
For that analysis, only fish that were age 4 and older 
were included, because that age was the first age at 
which skipped spawning was observed; in addition, 
only those ages that had a sample size of at least 2 
fish were included (ages 4-15) (Fig. 3). 
Age at maturity 
The age at maturity of sablefish on the shelf when fish 
that would skip spawning were classified as mature 
was dramatically different from the age at maturity 
when fish that would skip spawning were classified 
as immature (Fig. 4A). The 95% Cl of each maturity 
curve did not encompass the other curve. Classifying 
fish that would skip spawning as mature increased the 
proportion of fish mature at age. On the slope, age at 
maturity was also higher when fish that would skip 
spawning were classified as mature; however, there 
was not a significant difference (Fig. 4B). The large CIs 
for slope data can be at least partially attributed to 
smaller sample sizes. 
As with maturity data collected on the shelf, the age 
at maturity of the pooled samples was significantly dif- 
ferent when fish that would skip spawning were clas- 
sified as mature as opposed to immature (Fig. 4C, solid 
lines). The 050 % was 6.8 years when fish that would 
skip spawning were classified as mature, compared 
with 9.9 years when they were classified as immature 
(Fig. 4C, solid lines). When fish that would skip spawn- 
ing were classified as immature, ages at maturity on 
the slope and shelf were different. Pooled age at ma- 
turity was intermediate between the slope and shelf 
(Fig. 4C, gray lines). When fish that would skip spawn- 
ing were classified as mature, age at maturity on the 
shelf and slope matched closely (Fig. 4C, black lines). 
The similarity between the 2 age-at-maturity curves 
indicates that fish in both habitats are mature at the 
same age but that the majority of fish that would skip 
spawning reside on the shelf, at least during winter. 
When fish that would skip spawning were classified as 
either mature or immature, the pooled data were clos- 
er in value to the shelf data because there were more 
samples on the shelf. 
The logistic model fits to the age-at-maturity data 
from AFSC annual summer longline surveys were vari- 
able; « 5 Q% ranged from 5.5 to 8.6 years and the slope 
parameters ranged from 0.6 to 1.3 (Fig. 5A). In the 
winter survey, the proportion of mature fish at age was 
