502 
Abstract Atka mackerel, Pleuro- 
grammus monopterygius, growth data 
differed significantly by area for length 
and weight characteristics, suggesting 
that local aggregations of this species 
develop differential growth patterns. 
We analyzed length-at-age and weight- 
length growth patterns from over 500 
fish and 37 protein-coding gene loci to 
determine the relation among Atka 
mackerel stocks in the Aleutian Is- 
lands. However, the potential stock de- 
lineations based on the growth patterns 
were not supported by the genetic data. 
Atka mackerel showed a high degree 
of genetic variability. Variation was 
detected at 30 of 37 loci; 14 of the 30 
loci were variable at the P 0 95 level. Av- 
erage heterozygosity for 329 specimens 
was 0.137, an unusually high value for 
a marine fish. Between-sample varia- 
tion among samples was extremely low 
(F st = 0.004), suggesting considerable 
gene flow throughout the range repre- 
sented by the samples. On the basis of 
the genetic data, we cannot reject the 
null hypothesis that our samples came 
from a single genetically homogenous 
population of Atka mackerel. We pre- 
sume that gene flow occurs throughout 
the population through the dispersal of 
pelagic larvae and juveniles. We con- 
clude that despite genetic homogeniza- 
tion, phenotypic variation in Atka mack- 
erel adult life history stages warrants 
consideration by fishery managers. 
Manuscript accepted 17 September 1997. 
Fishery Bulletin 96:502-515 (1998). 
Geographic variation in genetic and 
growth patterns of Atka mackerel, 
Pleurogrammus monopterygius 
(Hexagrammidae), in the 
Aleutian archipelago 
Sandra A. Lowe 
Alaska Fisheries Science Center 
7600 Sand Point Way NE, BIN C 1 5700 
Seattle, Washington 981 I 5-007 0 
E-mail address: sandra.lowe@noaa.gov 
Donald M. Van Doornik 
Gary A. \X/i nans 
Northwest Fisheries Science Center 
2725 Montlake Blvd. E. 
Seattle, Washington 98112 
Atka mackerel, Pleurogrammus mon- 
opterygius , a member of the greenling 
family Hexagrammidae, is distrib- 
uted throughout the north Pacific 
Ocean, the southern Bering Sea, 
and the Gulf of Alaska. The center 
of abundance of this semipelagic 
species is the Aleutian Islands. 1 2 
Greenling larvae and fingerlings 
(25-30 mm) undergo a pelagic stage 
and assume an oceanic mode, dur- 
ing which time they reside in the 
surface layers of the open waters 
and migrate for considerable dis- 
tances out to sea (Gorbunova, 1962). 
Adult (3+ years) Atka mackerel are 
pelagic during much of the year (in 
waters <200 m depth) but migrate 
annually to moderately shallow wa- 
ters where they become demersal and 
spawn in areas of strong currents 
(Gorbunova, 1962). They have spe- 
cific spawning site preferences and 
spawning has been observed in island 
passes in the Aleutian, Shumagin, 
and Commander Island archipela- 
goes (Turner, 1886; Rutenberg, 1962). 
Historically, large inshore concen- 
trations of spawning Atka mackerel 
have been the target of subsistence 
fisheries by native Aleuts (Turner, 
1886 ). The first large-scale commer- 
cial catches in the Aleutian Islands 
and western Gulf of Alaska were 
taken by Russian fleets beginning in 
the early 1970s, followed by the Re- 
public of Korea, and to a lesser ex- 
tent, Japan in the early 1980s (Murai 
etal., 1981; Berger etal., 1986). Pres- 
ently, a U.S. trawl fishery harvests 
Atka mackerel from the eastern 
Bering Sea and Aleutian Islands re- 
gions, with minimal catches from the 
Gulf of Alaska. From 1992 to 1994, 
catches averaged about 70,000 met- 
ric tons (t) (valued at 17 million U.S. 
dollars [exvessel] in 1994) and in- 
creased to 104,000 t in 1996. 1,2 
1 Lowe, S. A., and L. W. Fritz. 1996a. 
Atka mackerel. In Stock assessment and 
fishery evaluation report for the ground- 
fish resources of the Bering Sea/ Aleutian 
Islands regions as projected for 1997, p. 
369-420. North Pacific Fishery Manage- 
ment Council, 605 W. 4th Avenue, Suite 
306, Anchorage, AK 99501-2252. 
2 Lowe, S. A., and L. W. Fritz. 1996. Atka 
mackerel . In Stock Assessment and Fish- 
ery Evaluation Report for the Groundfish 
Resources of the Gulf of Alaska as pro- 
jected for 1997, p. 331-361. North Pacific 
Fisheries Management Council, 605 W. 4th 
Avenue, Suite, Anchorage, AK 99501-2252. 
