FISHERY BULLETIN: VOL. 83, NO. 4 



Digestion was fairly slow in all species, taking at 

 least 9 to 12 h for a full stomach of food to be half 

 digested (Singer 1982). Ibgether, these indicate that 

 individuals may not need to feed every day and that 

 both within and among species these populations 

 may feed with a high degree of asynchrony (Singer 

 1982). 



Do the observed differences in diets suggest inter- 

 specific competition? Central to competition theory 

 is the presumption that individuals or populations 

 use the same or a very similar resource and that this 

 resource is in short supply (Pielou 1975; Pianka 

 1978). Abundances of all types of plankton used by 

 these fishes are high. The fact that individuals can 

 probably fill their stomachs in a very short time 

 period (Singer 1982) indicates that their needs are 

 easily met. This suggests that competition for food 

 does not play an important role in the foraging pat- 

 terns of these species. Other factors, such as the lack 

 of observed aggressive interactions within or among 

 the species studied in over 1,100 min of in situ 

 feeding observations, high overlap in time of feeding, 

 generally low similarity of diet, and high intraspecific 

 variability within foraging patterns suggest there 

 is little food competition (Singer 1982). 



Similarly, available evidence suggests little com- 

 petition for space among juveniles (Carr 1983). 

 When juveniles enter the kelp forest system, they 

 immediately occupy habitats characteristic of adults; 

 thus, habitat preference may be under some genetic 

 control. Close spatial co-occurrence with the absence 

 of agonistic interactions suggests that competition 

 for space is minimal in these fish. Also, within the 

 kelp forest studied, juvenile rockfishes are the 

 predominant planktivores, and are thus relatively 

 free of other possible competitors. Other kelp forest 

 planktivores such as Chromis punctipinnis, Oxy- 

 julius califomica, and Brachyistius frenata are pres- 

 ent, but in very low numbers, and often only for short 

 periods of time 



Thus, the differences in diet seen in this study ap- 

 pear to be the consequences of these species ex- 

 ploiting localized food resources encountered in dif- 

 ferent microhabitats. Competition for food does not 

 seem to be a strong ecological influence among these 

 juveniles. 



ACKNOWLEDGMENTS 



I thank Greg Cailliet, Milton Love, and Ralph Lar- 

 son for their guidance and suggestions throughout 

 this study. Many friends at Moss Landing assisted 

 me throughout this project including Gilbert Van 

 Dykhuizen, Bruce Welden, John Heine, Tim Herr- 



linger, and John Oliver, who gave helpful comments. 

 Mark Carr and Tbdd Anderson gave much needed 

 help and support in diving, stimulating comments, 

 and general assistance. Mark Silberstein and Peter 

 Slattery helped with invertebrate identification. 

 Statistical services were provided by Moss Landing 

 Marine Laboratories' HP9825 computers. The Peb- 

 ble Beach Corporation graciously allowed diving ac- 

 cess to Stillwater Cova Partial funding for equip- 

 ment came from the D & L Packard Foundation. 

 Thanks also to Sara Warschaw and Waheedah 

 Muhammad for typing this manuscript. 



Literature Cited 



Bray, R. N., and A. W. Ebeling. 



1975. Food activity, and habitat of three "picker-type" 

 microcarnivorous fishes in the kelp forest off Santa Barbara, 

 California. Fish. Bull., U.S. 73:815-829. 



Brodeur, R. D. 



1982. Food habits, dietary overlap and gastric evacuation rates 

 of rockfish (Genus Sebastes). M.S. Thesis, Oreg. State Univ., 

 Corvallis, 98 p. 



BURGE, R. T., AND S. A. Shultz. 



1973. The marine environment in the vicinity of Diablo Cove 

 with special reference to abalones and bony fishes. Calif. 

 Dep. Fish Game, Mar. Res. Tbch. Rep. 19, 433 p. 

 Carr, M. A. 



1983. Spatial and temporal patterns of recruitment of young- 

 of-the-year rockfishes (genus Sebastes) into a Central Califor- 

 nia kelp forest. M.A. Thesis, San Francisco State Univ., San 

 Francisco, 122 p. 



Chen, L. C. 



1971. Systematics, variation, distribution, and biology of the 

 subgenus Sebastomus (Pisces, Scorpaenidae, Sebastes). Univ. 

 Calif. Press, Berkeley 107 p. 



Coyer, J. A. 



1979. The invertebrate assemblage associated with 

 Macroq/stis pyrifera and its utilization as a food source by 

 kelp forest fishes. Ph.D. Thesis, Univ. Southern California, 

 Los Angeles, 364 p. 

 Davis, W. P., and R. S. Birdsong. 



1973. Coral reef fishes which forage in the water column, a 

 review of their morphology, behavior, ecology and evolu- 

 tionary implications. Helgo. Wiss. Meersunters. 24:292-306. 

 DeLacey, A. C, K. R. Hitz, and R. L. Dryfoos. 



1964. Maturation, gestation and birth of rockfish (Sebastodes) 

 from Washington and adjacent waters. Wash. State Dep. 

 Fish. Res. Pap. 2(3):51-67. 

 Dewitt, F. A., Jr., and G. M. Cailliet. 



1972. Feeding habits of two bristlemouth fishes, Cydothone 

 acclinidens and C. signata (Gonostomatidae). Copeia 

 1972:868-871. 



Hallacher, L. E. 



1977. Patterns of space and food use by inshore rockfishes 

 (Scorpaenidae; Sebastes) of Carmel Bay California. Ph.D. 

 Thesis, Univ. California, Berkeley, 119 p. 

 Hammer, R. M. 



1981. Day-night differences in the emergence of demersal 

 zooplankton from a sand substrate in a kelp forest. Mar. 

 Biol. (Berl.) 62:275-280. 

 HoBSON, E. S., and J. R. Chess. 



1976. Trophic interactions among fishes and zooplankters 



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