FISHERY BULLETIN: VOL. 82, NO. 2 



clusters in the fall, while Squalus acanthias and 

 Pseudopleuronectes americanus were common 

 co-group members during the fall cruises. In the 

 spring the latter species regularly occurred in a 

 separate group which included Gadus morhua and 

 Hemitripterus americanus. Except for Scophthal- 

 mus aquosus, an inshore resident, all of these 

 species are of boreal faunal affinity and are re- 

 stricted to cold water (Bigelow and Schroeder 

 1953; Leim and Scott 1966). 



Prionotus carolinus, Stenotomus chrysops, 

 Paralichthys dentatus, and Centropristis striata, 

 all warm-temperate species, were regularly clas- 

 sified in the same group during both seasons. Dur- 

 ing the fall this group was often joined by Mustelus 

 canis, another warm-temperate species which was 

 only rarely taken during the spring cruises. Two 

 other warm-temperate species, Peprilus triacan- 

 thus and Urophycis regia, regularly cooccurred 

 with this group in the spring. 



Merluccius bilinearis and Urophycis chuss were 

 the two most consistently cooccurring species, ap- 

 pearing in the same group in all but one cruise. 

 These two species formed the core of a third species 

 group which was ubiquitous in the spring and 

 widespread across the deeper portion of the study 

 area in the fall. Both of these boreal species have 

 broader temperature tolerances than the cold- 

 water groups noted above (Musick 1974; Bigelow 

 and Schroeder 1953). Abundances of these two 

 species were greater on the outer shelf and shelf 

 break, and they often clustered with Paralichthys 

 oblongus ( = Hippoglossina oblonga), an outer 

 shelf resident, and, in the fall, with Citharichthys 

 arctifrons, a slope resident which also occurs on 

 the outer shelf (Richardson and Joseph 1973) and 

 Lepophidium cervinum, another outer shelf resi- 

 dent. The warm-temperate species Peprilus 

 triacanthus and Urophycis regia were also com- 

 mon group members in the fall, while Lophius 

 americanus regularly occurred in this group in the 

 spring. 



The fourth clearly defined recurring species 

 group was an upper slope group composed of 

 Helicolenus dactylopterus, Chloropthalmus agas- 

 sizi, and Merluccius albidus, which appeared con- 

 sistently during both seasons. Urophycis tenuis 

 commonly cooccurred with members of this group 

 during the spring, while in the fall this species was 

 more widely distributed across the outer shelf and 

 tended to appear in small groups with Lophius 

 americanus and Glyptocephalus cynoglossus . 



The major recurring species groups described 

 above are listed for each season in Table 3. The 



groups are ordered in the same manner as the 

 generalized station groups, that is, from shal- 

 lowest to deepest (distribution) while still main- 

 taining nearest neighbor intergroup relationships 

 as determined in the clusters. Figures 9 and 10 

 show the distributional relationships between the 

 major site and species groups as determined by 

 nodal analyses. As noted above, these relation- 

 ships are more sharply defined during the spring 

 cruises than in the fall, but in both cases the nodal 

 analyses show clear differences in the faunal com- 

 position of site groups and the distribution of 

 species groups. The interrelationships seen here 

 are also highly representative of those noted dur- 

 ing analyses of the individual cruises. 



Dominance 



The dominant species for each of the pooled site 

 groups are given in Tables 4 and 5. During the 

 spring Limanda ferruginea was the major domi- 

 nant at the cold-water, inshore site group (I), 

 Squalus acanthias and Merluccius bilinearis were 

 among the major dominants at all site groups, and 

 Peprilus triacanthus was a major dominant at all 

 but the cold-water site group. Stenotomus 

 chrysops was a major dominant along the southern 

 outer shelf (group III). In the fall, the southern 

 inshore site group (I) was strongly dominated by 

 three warm-temperate species: Prionotus 

 carolinus, Stenotomus chrysops, and Peprilus 

 triacanthus. These three species persisted as 

 major dominants at the northern inshore site 

 group, but were joined there in roughly equal 

 dominance by three boreal species: Limanda fer- 

 ruginea, Squalus acanthias, and Merluccius 

 bilinearis. Peprilus triacanthus and the latter 

 group were major dominants on the northern 

 mid-shelf (group III). Peprilus triacanthus and 

 Merluccius bilinearis were also major dominants 

 at the outer shelf stations (group IV), where they 

 were joined by Urophycis regia. The shelf-break 

 stations (group V) were dominated by Merluccius 

 bilinearis, Citharichthys arctifrons , and 

 Helicolenus dactylopterus. 



There were few major changes in species domi- 

 nance throughout the study, and Tables 4 and 5 

 are representative of those for the individual 

 cruises. Merluccius bilinearis, Peprilus triacan- 

 thus, and Squalus acanthias were consistently the 

 three most dominant species during both major 

 seasons. Although Merluccius bilinearis ac- 

 counted for only around 107c of the individuals 

 taken, it was the most consistently dominant 



306 



