850 



Fishery Bulletin 100(4) 



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Greenstriped -- 





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Stripe tail 



Cowcod 



100 200 300 400 100 200 300 400 



Depth (m) 



Figure 8 



Plot of rockfish CPUE estimates by depth and latitude from the AFSC triennial 

 bottom trawl survey. Circle diameters are proportional to the square root of rockfish 

 CPUE and the bold plus symbol represents the centroid of the CPUE estimates. 



1996). Another potential criticism of bottom trawl gear is its 

 selectivity for capturing demersal fishes. Of the rockfishes 

 included in our analysis, shortbelly and widow rockfish are 

 two species that are known to be distributed in the water 

 column (Lenarz, 1980; Wilkins, 1986; Chess et al., 1988). De- 

 spite their occurrence off the bottom, however, both species 

 were captured with regularity in the bottom trawl survey 

 (Table 1). We conclude that, at least for the trawl sector of 

 the groundfish fishery, the results of our study should prove 

 useful in defining assemblages for rockfish management. 



As previously discussed, the assemblage descriptions 

 given in Table 4 contain some inconsistencies with respect 

 to the spatial distributions of the species. These apparent 

 misclassifications may be the result of temporal variability 

 in total rockfish abundance, as was captured by the second 

 dimension of the MDS analysis. Because the estimated 

 abundance of a species in our analysis was influenced by 

 population levels of the stock at the time of each survey, 

 which can change over time, our pooled analysis may not 

 provide the best indication of historical assemblage asso- 



