316 



Fishery Bulletin 100(2) 



100-200 



Bottom depth (m) 



B 



g 

 a. 



20^0 nmi 



Distance from land (nmi) 



0.2 - 



o^^ 



Shumagin Chinkof Kodiak 



Geographic region 



Figure 7 



Proportion of stations where low-density concentrations 

 I < 1000 fish/km- 1 of adult walleye pollock were obsei'ved, 

 binned by bottom depth (A), distance from land (B), and 

 geographic region (C). 



and Gilbert, 1880)), Pacific halibut iHippoglossus stenole- 

 pis Schmidt, 1904), Pacific cod iGadux macrocephalus Tile- 

 sius, 1810), sablefish (Anoplopoma fimbria (Pallas, 1814)), 

 Dover sole (Microstomus pacificus (Lockington, 1879)), and 

 rex sole (Glyptocephalus zachirus Lockington, 1879). This 

 small cluster was usually isolated from the larger main 

 cluster (i.e. high dissimilarity between the two clusters). 

 Adult pollock were also clustered separately from the juve- 

 nile pollock age groups. In all years except 1987, age-1 

 and age-2 pollock were clustered with each other, whereas 

 age-0 pollock were clustered separately. In 1987, age-0 and 

 age-1 pollock clustered together, although not as closely 

 associated as ages 1 and 2 in the other years. Until 1996, 

 age-0 pollock clustered with Pacific sleeper shark (Som- 



BI984 



 1987 

 D1990 



 1993 

 B1996 



CD ^> CD c= 



C5 C2 CD C^ 



— — C=y CD 





_JiB 



— CD — CD 

 C3 CD CD =^ 



^ CD CD CD 



— — C=^ CD 



 — CD ; 



CPUE (number of fish/km^) 



Figure 8 



Proportion of stations with different levels of juvenile wall- 

 eye pollock CPUE; age (A), age 1 (B), and age 2 (C). 



niuaus pacificus Bigelow and Schroeder, 1944), Aleutian 

 skate (Bathyraja aleutica (Gilbert, 1896)), or silvergray 

 rockfish iSebastes brevispinis (Bean, 1884)). In the larger 

 cluster that contained all the juvenile pollock age groups, 

 it was common to find Pacific herring iClupea pallasii 

 (Cuvier and Valenciennes, 1847)) in all years. 



Cluster analysis by station of the triennial data result- 

 ed in clusters that fell into clean zoogeogi'aphic groups 

 that followed depth contoiu-s. Maps of clusters identified 

 seven groups of species that could be tracked in the GOA 

 throughout most years (Table 9). Groups 1, 2, and 5 were 

 present only in 4 out of the 5 triennial survey years. In 

 1984, groups 2 and 5 were absent whereas in 1990, group 

 1 was absent. The species within each cluster were listed 

 m order of dominance. Although many of the clusters had 



