305 
Abstract — Over 34,000 age 0-2 ju- 
venile sablefish ( Anoplopoma fimbria) 
were tagged and released in southeast 
Alaska waters during 1985-2005. The 
data set resulting from this tagging 
study was unusual because of its 
time span (20 years) and because age 
could be reliably inferred from release 
length (i.e., tagged and released fish 
were of known age); thus, age-specific 
movement patterns could be examined. 
The depth- and area-related recovery 
patterns supported the concepts that 
sablefish move to deeper water with 
age and migrate counterclockwise 
in the Gulf of Alaska. Availability 
to the fishery increased rapidly for 
fish of younger ages, peaked at age 
5 to 6, and then gradually declined 
as sablefish moved deeper with age. 
Decreased availability with age may 
occur because of lower fishing effort 
in deep water and could have sub- 
stantial implications for sablefish 
stock assessments because “dome- 
shaped” availability influences the 
reliability of abundance estimates. 
The area-related recovery pattern was 
not affected by year-class strength; 
i.e., there was no significant density- 
dependent relationship. 
Manuscript submitted 4 December 2007. 
Manuscript accepted 4 April 2008. 
Fish. Bull. 106:305-316 (2008). 
The views and opinions expressed or 
implied in this article are those of the 
author and do not necessarily reflect 
the position of the National Marine 
Fisheries Service, NOAA. 
Age-specific movement patterns 
of sablefish ( Anoplopoma fimbria) in Alaska 
Nancy E. Maloney (contact author) 
Michael F. Sigler 
Email address for N. E. Maloney: Nancy.Maloney@noaa.gov 
National Oceanic and Atmospheric Administration 
National Marine Fisheries Service 
Alaska Fisheries Science Center, Auke Bay Laboratories 
Ted Stevens Marine Research Institute 
17109 Point Lena Loop Road 
Juneau, Alaska 99801 
The general migration pattern of 
sablefish (Anoplopoma fimbria) in the 
northeast Pacific Ocean was deduced 
in the 1980s from several tagging 
studies (Bracken, 1983; Beamish 
and McFarlane, 1988; Fujioka et al., 
1988;) and enlarged upon in further 
studies over the following two decades 
(Heifetz and Fujioka, 1991; Rutecki 
and Varosi, 1997; Kimura et al., 1998; 
Maloney, 2004). In southeast Alaska, 
juvenile sablefish that are spawned 
offshore appear in inshore waters in 
late summer or early fall and spend 
the first year or two of life in shallow 
coastal bays and inlets before moving 
into progressively deeper water. At 
the same time that they are moving 
into deeper water, many young sable- 
fish move north and west on a migra- 
tion path that takes them across the 
Gulf of Alaska to the Aleutian Islands 
and Bering Sea. Eventually, most will 
return to the eastern Gulf of Alaska 
as adults. 
The sablefish fishery in the Gulf of 
Alaska (GOA), eastern Bering Sea, 
and Aleutian Islands is managed by 
the National Marine Fisheries Ser- 
vice (NMFS) in cooperation with the 
North Pacific Fishery Management 
Council. Sablefish in these areas are 
assumed to belong to one population 
(Kimura et al., 1998), for which a to- 
tal allowable catch is calculated each 
year and apportioned among six man- 
agement areas. The annual quotas 
for each area are based on the distri- 
bution of biomass among the areas, 
which is estimated from longline sur- 
veys and commercial catches (Heifetz 
et al., 1997). Because sablefish are 
known to be migratory, estimates of 
the rates of migration between ar- 
eas could affect the apportionment 
of quotas among management areas 
(Heifetz et al., 1997). 
Migration rates between areas 
have been estimated from tag data 
by using fish-length classes in the 
modeling process (Heifetz and Fu- 
jioka, 1991). Although fish-length 
data are commonly available, actual 
age data are generally scarce. Age 
data are preferable to length data for 
estimating population age structure 
(Sigler, 1999), but sablefish are diffi- 
cult to age, especially for ages great- 
er than 5 or 6 years (Kimura and 
Lyons, 1991). Tagging of known-age 
juveniles before they leave coastal 
areas offers an opportunity to docu- 
ment age-specific movements. Age 
0-2 (mostly age 1) sablefish have 
been tagged annually since 1985 in 
bays and inlets of southeast Alas- 
ka. The objective of our study was 
to determine movement patterns of 
sablefish based on these known-age 
fish, using a unique 20-year data 
set of age-specific mark-recapture 
data. Specifically, we determined 1) 
how the depth inhabited by sablefish 
changes with age; 2) how the area 
inhabited changes with age; 3) how 
availability to the primary fishery 
(longline) changes with age; and 4) 
whether there is a density-dependent 
effect of year-class strength on the 
extent of migration of young sable- 
fish. Results of objectives 1 and 2 
largely confirmed the results of pre- 
vious studies, whereas objectives 3 
and 4 were new. 
