Williams and Ralston Distribution and co occurrence of Sebastidae off California and Oregon 



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Figure 7 



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

 bottom trawl sur\'ey. Circle diameters are proportional to the square root of rockfish 

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



be fairly constant at -200-250 m across all latitudes in- 

 cluded in our study. 



The ridge of increased species richness indicated that 

 there is substantial overlap in rockfish distributions. The 

 analysis of rockfish overlap in our study was computed in 

 two ways, i.e. by smoothed depth-latitude abundance and by 

 raw trawl catches. The smoothed species-specific abundance 

 estimates for all depth-latitude combinations could not be 

 presented here because of space limitations. However, such 

 data could be useful for detailed spatial analyses of rockfish 



co-occurrences in future analyses. The trawl-catch overlap 

 data represent the best estimate of bottom trawl co-occur- 

 rence probabilities for the study area. A potential limitation 

 of the overlap estimates presented in our study is that they 

 came from only one survey, which employed a single sam- 

 pling gear However, the bottom trawl gear used in the AFSC 

 triennial survey is generally similar to the fishing gear used 

 by commercial fishermen, and previous studies have shown 

 that catch rates from the continental shelf bottom trawl 

 survey closely match commercial catch rates (Fox and Starr, 



