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Fishery Bulletin 106(3) 
Recovery age (yr) 
Figure 3 
Tag recoveries from sablefish ( Anoplopoma fimbria) tagged as juveniles, by age 
and area. The size of the circles is proportional to the number of recoveries and 
represents a range from 1 to 43 recoveries. GOA=Gulf of Alaska. 
(Fig. 3). By ages 5 and 6 years, many fish had reached 
the western areas. Age 5 was the most common age of 
recovery for the western GOA and Aleutian Islands, 
and age 6 for the Bering Sea. Some fish aged 7-9 years 
remained in the western areas, but most had begun 
a return to the east. In the central GOA and eastern 
GOA outside waters, the 7-9-year-olds were mostly 
found in the 501-700 m depth range and were some 
of the most numerous fish. Fish aged 6-9 years were 
the most commonly recovered in the waters off British 
Columbia and may also have been fish returned from a 
westward migration (Fig. 4). A few fish may have come 
from eastern GOA inside waters (Chatham Strait), but 
Maloney and Heifetz (1997) found that this area has a 
high proportion of non-migrating fish. The most common 
depth stratum for fish recovered in British Columbia was 
the 501-700 m stratum. 
Availability to the fishery by age 
The model of availability at age fit the observed pat- 
tern of tag recoveries well. Deviances were scattered 
symmetrically around zero for most ages (Fig. 5). Only 
for ages 2 and 13 were there noticeable biases. The full 
model that assumed separate selectivity functions for 
the open access and IFQ fisheries significantly improved 
model fit, compared to a single selectivity function (Like- 
lihood ratio test, % 2 =220.1, df=3, P<0.001). The assump- 
tion of separate calibration coefficients rather than a 
single calibration coefficient also significantly improved 
fit (likelihood ratio test, x 2 = 189.7, df=l, P<0.001). 
Including parameters to allow availability to decrease 
for older ages (y for 1985-94 and 1995-2005) signifi- 
cantly improved fit compared to a reduced model with 
asymptotic availability (likelihood ratio test, % 2 = 686.7, 
df =2, PcO.OOl). 
Juvenile sablefish first became available to the com- 
mercial fishery at age 2. Availability rapidly increased 
such that by age 5, nearly all sablefish were avail- 
able to the commercial fishery (Fig. 6). Both the age 
at 50% availability and the age at 100% availability 
values were one year greater (older) in the IFQ fishery 
than in the open access fishery (4 years versus 3 years 
and 6 years versus 5 years, respectively). Availability 
decreased for older ages, such that by 15 years, avail- 
ability was 50% for the open access fishery and 20% 
for the IFQ fishery. The degree of dome shape was 
sensitive to the assumed value of M; for example, by 
15 years, availability for the open access fishery was 
70% for M = 0.12 compared to 50% for the assumed 
value of M = 0.10. 
Density-dependent effect on migration 
We tested whether year-class strength affected the pro- 
portion of recoveries in the western areas, hypothesizing 
that a density-dependent effect would cause more recov- 
eries in western areas for strong year classes. There was 
no significant relationship (regression, df=14, P=0.18) 
because about 20% of recoveries occurred in western 
areas, regardless of year-class strength (Fig. 7). In the 
regression, the proportion was transformed by arcsin squar- 
eroot, as is recommended to normalize data expressed 
as proportions (Zar, 1984). 
