Kimura et al.: Stock structure and movement of Anoplopoma fimbria 
467 
Figure 1 
Map of 27 areas (described in Table 2) used in this paper to describe analysis of 
sablefish tag-recovery data. Principal regions are also described in Table 2. Also shown 
are the 400-m depth contour, which is the approximate habitat of adult sablefish, and 
the oceanographic circulation that are hypothesized to affect movements of sablefish. 
Migration from Alaska to the west coast 
A well-defined sablefish migration seems to occur 
from Alaska to the northern portion of the west coast. 
To explore this phenomenon, we plotted the number 
of tag recoveries from Alaska, recovered along the 
west coast, against upwelling strength in the north- 
ern portion of the west coast. Length frequencies from 
Alaska and west coast sablefish trap index surveys 
(Parks and Shaw, 1983) were also used to examine 
the hypothesis that a substantial mixing of large ( >60 
cm) sablefish of Alaska origin occurs in west coast 
sablefish stocks from Vancouver Island and Wash- 
ington State to California’s San Francisco Bay. 
Results 
Descriptive results 
Tag recovery rates by fishing gear type used for ini- 
tial capture show that the tag recovery rate for trap 
gear (12.4%) is twice that for longline (5.87%) and 
trawl (5.12%) gears (Table 1). Because these results 
hold for fish tagged in Alaska and off the west coast, 
it is likely that the much higher tag recovery rate for 
trap gear is due to the superior condition of and pre- 
sumably lower mortality rate for trap-caught fish. 
Tag recovery rates were remarkably consistent for 
all areas of tagging (Table 4). This finding would 
suggest that the exploitation rate for sablefish stocks 
are similar throughout the northeast Pacific. Recov- 
ery rates were higher along the west coast (8.4%) 
than from Alaska waters (6.0%). This is just about 
the magnitude that would be expected when taking 
into account the mixtures of gears used for tagging 
(i.e. if we apply both the recovery rates for trawl and 
trap caught fish observed from the west coast and the 
longline recovery rate observed in Alaska to the num- 
bers released in Alaska, we would arrive at the 6% re- 
covery rate that was actually observed in Alaska). 
Sablefish are long-lived; ages over 40 yr are regu- 
larly documented (Kimura et al., 1993) and a maxi- 
mum recorded age of 94 yr has been recorded at AFSC 
( Anderl 5 ). The instantaneous natural mortality rate 
5 Anderl, D. M. 1997. Age and Growth Task, Alaska Fisheries 
Science Center, Natl. Mar. Fish. Serv., NOAA, 7600 Sand Point 
Way NE, Seattle, WA 98115. Personal commun. 
