GROUP 2 



Yellowfin sole 

 Alaska plaice 

 Sturgeon poacher 

 Pacific herring 

 Capelin 



1/5 



Elbow crab 



6/15 



18/50 



GROUP 1 



Pollock 



Snow crab (opilio) 

 Rock sole 

 Snow crab (bairdi) 

 Pacific cod 

 Flathead sole 

 Greenland turbot 

 Snow crab (hybrid) 

 Unidentified skates 

 Pink shrimp 



15/30 



GROUP 4 



Arrowtooth flounder 

 Pacific halibut 

 Rex sole 



GROUP 5 



Red king crab 

 Longhead dab 

 Starry flounder 



GROUP 3 



Bering flounder 

 Red Irish lord 

 Pink snailfish 



Figure 22.— Recurrent species groups observed in Ihe Bering Sea during Ihe 1976 spring trawl survey and their relationships. Species are 

 listed in order of relative abundance within each group. Fractions indicate the ratio of the number of observed species-pair affinities be- 

 tween groups to the maximum number of possible connections (maximum possible connections for any two groups = product of 

 number of species within both groups). Dotted lines indicate associated taxa showing affinity with some group members, but not all. 



The total apparent population biomass of walleye pollock 

 within the study area was 0.679 million t (95% confidence limits 

 0.480-0.879 million t), which appeared to be a relatively low 



estimate. During 1970-75, commercial catches of walleye pollock 

 from the study area by Japan alone ranged from 0.6 to 1 .2 million 

 t/yr. The total Japanese walleye pollock catch during the period 

 November 1975 to October 1976 was 0.8 million t. Another com- 

 parison indicating that the 1976 survey estimate for walleye 



pollock biomass was low was the 1975 survey estimate of 2.43 

 million t (95% confidence limits 2.00-2.85 million t) from the 

 same region (Pereyra et al. see footnote 2). 



Possible causes of the low estimate of walleye pollock biomass 

 for 1976 include 1) decreased catchability — the availability of 

 walleye pollock to demersal survey trawling may have been low 

 because some of the population was off bottom for spring spawn- 

 ing (Serobaba 1974); 2) emigration— seasonal and environmental- 

 ly related shifts in geographical distribution may have decreased 

 the proportion of the eastern Bering Sea population of walleye 

 pollock within the survey area, as a result of cold temperatures 

 and heavy ice cover over the continental shelf during spring 1976; 

 and 3) true decline — an actual decrease in population biomass 

 may have occurred between 1975 and 1976 as a result of natural 

 and fishing mortalities. 



34 



