FISHERY BULLETIN: VOL. 82. NO. 1 



tion was also made at the edge of a kelp forest, so 

 comparison with our areas is warranted. 



The comparatively large standing stock of fishes at 

 SOK in part reflects the nature of the kelp forest off 

 San Onofre. This kelp forest was located in relatively 

 deep (15 m) water, and was of moderate (0.1 adult 

 plant/m 2 ; Dean footnote 4) kelp density, with a sur- 

 face canopy. Both of Quast's (1968b) sites were 

 located in relatively shallow (7.6-10.7 m) water. 

 Furthermore, Quast's Bathtub Rock site lacked a 

 surface kelp canopy. A substantial part of the fish 

 biomass we observed at San Onofre was in the exten- 

 sive canopy and midwater zones. Nearly half of the 

 biomass occurred in the upper two strata at each site, 

 and about one-quarter occurred in the midwater (7.6 

 m) stratum alone. The contribution of the upper 

 water column to overall standing stock is also illus- 

 trated by the relative importanceof the cosmopolitan 

 species. Ranging throughout the water column, kelp 

 bass, white seaperch, and sehorita comprised about 

 60% of total biomass at the San Onofre kelp bed. The 

 relative contribution of water-column species to 

 overall standing stock would be lower in kelp forests 

 anchored on high-relief rock, because reef-de- 

 pendent species would be more abundant than at San 

 Onofre. However, the presence of an extensive 

 bathymetric zone from the canopy into midwaters 

 provided space, forage, and orientation for a substan- 

 tial standing stock of fishes in the San Onofre kelp 

 bed. The lack of such an extensive midwater zone 

 may have limited the abundance of canopy and cos- 

 mopolitan species at Bathtub Rock and Del Mar, 

 accounting, in part, for the relatively low estimates of 

 standing stock in these areas. 



Our study, then, suggests that kelp per se can 

 enhance the potential standing stock of fishes in an 

 area. Our kelp-forest areas lacked a high-relief bot- 

 tom and the species of fish that depend on it. The 

 remaining fish were those that either tolerate or are 

 not influenced by a cobble bottom, and those that 

 depend intimately on kelp. Yet the standing stock of 

 fishes at the San Onofre kelp bed was substantial. 

 The reduced numerical abundance of fishes and 

 smaller biomass (excluding barred sand bass) in our 

 kelp-depauperate area further indicates the impor- 

 tance of kelp at San Onofre. Experimental manipula- 

 tion of kelp density is probably the best test of the 

 influence of kelp on fish abundance (Miller and 

 Geibel 1973; Bray 198 1; M. Carr footnote 3). We also 

 recognize that large-scale oceanographic factors may 

 strongly affect survivorship of planktonic larvae and 

 the subsequent abundance of juvenile and adult 

 fishes (Stephens and Zerba 1981; Parrish et al. 

 1981). However, our comparisons indicate that giant 



kelp, even in only moderate density, was necessary 

 for the existence of a large standing stock of diverse 

 fishes in cobble-bottom areas. We conclude that, 

 while rock reefs enhance the fish fuana of an area 

 whether or not there is kelp, the presence of kelp in an 

 area of low-relief bottom also augments the abun- 

 dance of juvenile and adult fish on a local scale. Kelp 

 may also contribute strongly to the standing stock of 

 fish in areas of high-relief bottom, but no one to date 

 has adequately evaluated this hypothesis. We pre- 

 dict that the densities of canopy species and cos- 

 mopolites like kelp bass and sehorita will also prove 

 to be related to the density of giant kelp on high- 

 relief bottoms. 



ACKNOWLEDGMENTS 



We thank Ken Plummer and Mark Wilson for assis- 

 tance with filming cinetransects. Sandy Larson and 

 Jan Fox typed versions of the manuscript. Diane 

 Fenster drafted Figures 2-4. This paper is a result of 

 research funded by the Marine Review Committee 

 (MRC), Encinitas, Calif. The MRC does not 

 necessarily accept the results, findings, or con- 

 clusions stated herein. A. W. Ebeling kindly loaned 

 the cameras and housings used in the study. 



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