514 



Fishery Bulletin 90(3). 1992 



Even so, high dietary overlap observed among co- 

 occurring pelagic juvenile rockfishes suggests that 

 similar recruitment dynamics must exist if the distribu- 

 tion and abundance of foods has a major impact on 

 recruitment. 



Intraspecific spatial variation was observed (Table 

 7), even though substantial interspecific overlap exists 

 in patterns of food utilization. In some instances, 

 parallel spatial differences were observed for different 

 species. For example, in 1987 both widow and short- 

 belly rockfish fed on euphausiid eggs to a much greater 

 extent in deep water (>100m) than in shallow water. 

 In other cases, however, species-specific differences in 

 diet due to depth were reversed. In 1987, for exam- 

 ple, the consumption of Calanus spp. copepods by 

 chilipepper was higher in shallow water, while con- 

 sumption by widow rockfish was higher in deep water. 



With the exception of the predator-size MANOVA 

 discussed previously (i.e., shortbelly rockfish in 1985), 

 sample sizes for each treatment combination in all 

 MANOVA tests were reasonably well balanced. There- 

 fore, it is unlikely that our conclusions were compro- 

 mised by our choice of statistical tests. 



The spatial incongruity of within-year dietary pat- 

 terns among species also extended to interannual 

 within-species comparisons. For example, shortbelly 

 rockfish sampled in 1984 and 1987 consumed substan- 

 tially fewer Calanus spp. copepods in the shallow 

 southern quadrant than anywhere else. However, in 

 1986 consumption of this prey was greatest in fish 

 taken in this region. 



These interspecific (within-year) and interannual 

 (within-species) comparisons demonstrate a lack of 

 stability in the specifics of how spatial dietary effects 

 are expressed. It is likely that the complex nearshore 

 pattern of circulation that characterizes the study area 

 (frontal structures, mesoscale eddies, turbulent jets, 

 and upwelling plumes are common recurrent features; 

 Mooers and Robinson 1984, Flament et al. 1985, Njoku 

 et al. 1985, Schwing et al. 1990) defines the spatial 

 distribution of the zooplanktonic animals upon which 

 these rockfish feed. Thus, the dynamic nature of the 

 physical environment off central California generates 

 spatial instabilities in the distribution and abundance 

 of prey. 



Acknowledgments 



We are grateful to all personnel of the Tiburon Lab- 

 oratory, Southwest Fisheries Science Center, National 

 Marine Fisheries Service, particularly the staff of the 

 Groundfish Analysis Investigation, who participated in 

 the juvenile rockfish recruitment surveys in 1984-87. 

 We thank Master Milt Roll and the officers and crew 



of the RV David Starr Jordan for their valuable help 

 in collecting juvenile rockfish during these research 

 cruises. Sharon Moreland (currently of the Army Corps 

 of Engineers) taught us identification techniques for 

 young-of-the-year pelagic juvenile rockfish. Tony Chess 

 (Tiburon Laboratory) assisted with identification of 

 copepods, and Margaret Knight (Scripps Institute of 

 Oceanography) confirmed identification of the euphau- 

 siid eggs. Jim Bence (Tiburon Laboratory) generously 

 assisted us with statistical analyses. This paper was 

 greatly improved by thoughtful, constructive reviews 

 by Pete Adams, Jim Bence, George Boehlert, Ted Hob- 

 son, Ralph Larson, Bill Lenarz, Jeannette Whipple, and 

 three anonymous reviewers. 



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