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Fishery Bulletin 98(1) 



on midwater structure included juvenile greenspot- 

 ted and flag rockfishes, as well as sharpnose seap- 

 erch, pile perch, and blacksmith. 



Among platform comparisons The midwater assem- 

 blages also differed among rigs, although the vari- 

 ability was less than among the bottom assemblages. 

 Species richness ranged from 6 to 11 species per 

 platform (Fig. 7A). Species diversity also showed less 

 variability among platform midwaters than platform 

 bottoms (midwater H' range; 0.7 to 1.8, Fig. 7A). 



The midwater around platform Irene was dom- 

 inated by widow rockfishes (primarily YOYs, but 

 also one-year-old fishes), unidentified YOY rockfishes 

 (probably primarily widow rockfish) and YOY bocac- 

 cio. Almost no other fishes were noted (Table 6). The 

 species composition at platforms Hidalgo and Harvest 

 was similar to that at platfrom Irene, although painted 

 greenling were also occasionally seen. Far fewer fishes 

 were noted at platform Hermosa, although the spe- 

 cies composition was similar, with the addition of 

 small numbers of Pacific hake. Fewer fishes were 

 seen at platform Holly. Here, YOY rockfish (probably 

 widow rockfish), painted greenling, sharpnose sea- 

 perch and squarespot rockfish were the most common 

 species. Smaller numbers of juvenile widow rockfish, 

 YOY rockfish, and juvenile chilipepper characterized 

 platform Grace. We saw fewest fishes in the midwa- 

 ters around platform Gail where YOY rockfish (again 

 probably widow rockfish) were the most common. 



In general, the platforms at the western end of 

 the Santa Barbara Channel harbored a higher den- 



sity of fishes in the midwater than did those towards 

 the east (Fig. 7B). There was a significant rela- 

 tionship between density and northwest-southeast 

 rank (Spearmans r^=0.89, P=0.006). This pattern 

 was due to higher density of YOY rockfishes, espe- 

 cially widow rockfish and bocaccio, at platforms Irene 

 and Hidalgo. YOY rockfishes were abundant only at 

 Irene and Hidalgo, they were much less common at 

 the platforms farther east. There was not a signifi- 

 cant relationship between biomass and northwest- 

 southeast rank (Spearmans r^-0.64, P=0.11). 



Length-frequency comparisons 



Relatively few species were abundant in both the mid- 

 water and bottom assemblages. For those species that 

 were found in both environments, such as copper, 

 flag, and greenspotted rockfishes, there was a ten- 

 dency for juveniles to be found in the midwater and 

 older individuals on the bottom. Bocaccio were the 

 extreme example, with smaller juveniles occurring 

 only in midwater and larger individuals only on the 

 bottom (Fig. 8). The painted greenling was one of the 

 few species that occurred in virtually all size classes 

 in both the midwater and on the bottom (Fig. 8). 



There were considerable differences in the size fre- 

 quencies of the major species around the platforms 

 (Fig. 8). Some species, such as copper rockfish and 

 vermilion rockfish, were found primarily as juveniles 

 and subadults. At the extreme, we did not identify any 

 mature widow rockfish. Numerous other species (i.e. 

 painted greenling, bocaccio, greenspotted rockfish, 



