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Fishery Bulletin 100(4) 



due to the precipitous Big Sur coastline, with its marked 

 reduction in the amount of trawlable habitat in the 

 50-500 m depth range. Morever, the 1980, 1983, and 1986 

 surveys did not sample south of Monterey Bay. Similarly, 

 the increase in the number of samples in the 37.0-39.0°N 

 area (Fig. 3) was attributable to an increase in the total 

 amount of shelf habitat in that region (Fig. 2). Starting at 

 the shallowest depths, there was a tendency for the size 

 of the total rockfish catch to increase to a maximum in 

 deeper waters just beyond the shelf break (-200 m), fol- 

 lowed by a slight decrease in catch in the deepest waters 

 (Fig. 3). Not apparent to the eye in Figure 3 is a slight, but 

 significant trend in the distribution of sample locations 

 towards deeper waters at more southerly sites (linear 

 slope=-0.26, P-value=0.0041 ). This was probably due to 

 the decreasing amount of shelf habitat and the increas- 

 ing quantity of slope habitat as one moves south along the 

 California coast (Fig. 2). 



The amount of interspecific overlap in spatial distribu- 

 tions among the subset of 26 species differed, depending 



on whether co-occurrence was assessed from a categori- 

 zation of the catches into depth-latitude intervals or by 

 specific trawl locations (Tables 2 and 3). As expected, 

 depth-latitude overlaps were greater than the site-specific 

 trawl catch overlaps, due to the effect of spatial smoothing. 

 Inspection of the depth-latitude species overlaps (Table 2) 

 indicated that stripetail (S. saxicola), splitnose, chilipep- 

 per (S. goodei), bocaccio, and shortbelly iS. jordani) rock- 

 fish were most widespread with respect to co-occurrence 

 with other rockfishes. Similarly, overlaps measured from 

 actual trawl catches indicated that bocaccio, chilipepper, 

 stripetail, canary, and widow rockfish have relatively high 

 likelihoods of co-occurring with other rockfish species 

 (Table 3). 



The spatial distribution of rockfish over the continental 

 shelf and slope generally indicated a ridge of increased di- 

 versity at approximately 250 m depth, at least for samples 

 taken at northern latitudes (38.0-43.0°N) (Fig. 4). In 

 contrast, for southern latitudes (34.0-38.0°N), the ridge 

 of high diversity veered well offshore to a depth of 450 



