462 
Stock structure and movement of 
tagged sablefish, Anoplopoma fimbria, 
in offshore northeast Pacific waters 
and the effects of El Nino-Southern 
Oscillation on migration and growth 
Daniel K. Kimura 
Allen M. Shimada 
Franklin R. Shaw 
Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
7600 Sand Point Way NE, Seattle, WA 98 1 1 5-0070 
E-mail address (for D.K. Kimura): Dan.Kimura@noaa.gov 
Abstract .-Sablefish in the north- 
east Pacific are found in commercial 
quantities from the Bering Sea, the 
Aleutian Islands, throughout the Gulf 
of Alaska, and south along the west 
coast of Canada and the U.S. to Baja 
California. Tag-recovery data support 
a two-population hypothesis through- 
out the North American range: an 
Alaska population ranging from the 
Bering Sea, including the Aleutian Is- 
lands and extending down through the 
Gulf of Alaska to northwest Vancouver 
Island, Canada; and a west coast popu- 
lation extending from southwest Van- 
couver Island to Baja California. Tag 
recoveries indicate that these two popu- 
lations mix off southwest Vancouver Is- 
land and northwest Washington, and to 
a lesser extent off southern Washing- 
ton and Oregon. 
Alaska sablefish, which commonly 
migrate over 500 n mi, are more mo- 
bile than west coast sablefish. Tag re- 
coveries for sablefish tagged in Alaska 
have shown strong mutual exchanges 
between nearly all areas. In contrast, 
west coast sablefish have shown far less 
migratory behavior. Tagging data with 
respect to bathymetry are difficult to 
interpret in both regions owing to the 
fact that tagging and recovery effort do 
not cover the full bathymetric range of 
adults. 
Results of analysis of tag-recapture 
growth data were consistent with pat- 
terns observed for several other pelagic 
and demersal species. That is, El Nino- 
Southern Ocean Oscillation events ap- 
peared to retard the growth of sable- 
fish along the west coast and to enhance 
growth of Alaska sablefish. The timing 
of recoveries from sablefish tagged off 
Alaska and recovered off southwest 
Vancouver Island and Washington- 
Oregon suggests that movement south 
correlates positively with strong up- 
welling in this southern area. Although 
sablefish trap-index surveys show a 
north to south cline in the percentage 
of large sablefish ( >60 cm, and possi- 
bly of Alaska origin) sampled in length 
frequencies along the west coast, we 
were unable to correlate annual fluc- 
tuations in these percentages with up- 
welling strength. 
Manuscript accepted 23 September 1997. 
Fishery Bulletin 96:462-481 (1998). 
Adult sablefish have a proclivity for 
great depths (200-1500 m) where 
the ocean environment is relatively 
constant over extensive geographic 
distances and consequently can be 
found from central Baja California 
along the Pacific coast through the 
Gulf of Alaska and Aleutian Islands, 
along the Bering Sea slope to the 
Russian coast, and down the Kam- 
chatka Peninsula all the way to 
southern Japan (OCSEAP, 1986; 
Allen and Smith, 1988). 
The marked absence of sablefish 
eggs and larvae from the Bering Sea 
above 55°N is usually attributed to 
an intolerance to low (<2°C) tem- 
peratures (OCSEAP, 1986). Sable- 
fish occurrence in the Bering Sea 
and Aleutian Islands is thought to 
be dependent on egg and larval drift 
from the northeast Pacific, princi- 
pally through westward transport 
from the Gulf of Alaska by the Alas- 
kan Stream (OCSEAP, 1986). Al- 
though sablefish occur along the 
coast of Asia, only adult fish (>2 yr) 
are found (Kodolov, 1968) and they 
are believed to have been recruited 
from the northeast Pacific stock. 
Ocean currents from the western 
Bering Sea favor dispersal of sable- 
fish along the Asian coast by means 
of the East Kamchatka and Oyashio 
Currents. 
Commercial catches of sablefish 
appear to be absent off Japan 
(Chikuni, 1985). We do not know if 
commercial catches of sablefish oc- 
cur off Russia, although Kodolov 
(1968) describes the adult distribu- 
tion of sablefish as extending from 
the Bering Sea all along the Kam- 
chatka Peninsula. In contrast, 
sablefish is an important commer- 
cial species throughout the north- 
east Pacific with average annual 
landings (1984-93) of 2150 t for the 
eastern Bering Sea, 2405 t for the 
Aleutian Islands, 22,590 t for the 
Gulf of Alaska, 4835 t for British 
Columbia, Canada, and 11,129 t for 
the U.S. West Coast. 1 
Sablefish fecundity is determi- 
nate and eggs are spawned in three 
or four batches (Hunter et al., 1989; 
Macewicz and Hunter, 1994); eggs 
are semipelagic (McFarlane and 
Beamish, 1992) and have been 
found at depths ranging from 200 
to 800 m (Thompson, 1941; Kodolov, 
1968; Moser et al. 1994). Age-0 (yr) 
larvae initially inhabit offshore sur- 
face waters (McFarlane and Beam- 
ish, 1992), move inshore during the 
1 Aleutian Islands and eastern Bering Sea 
catches (Lowe, 1995), Gulf of Alaska 
catches (Fujioka, 1995), Canadian west 
coast catches (Saunders et al., 1995), U.S. 
west coast catches (Methot et al., 1994). 
