FOOD HABITS OF JUVENILE ROCKFISHES (SEBASTES) 

 IN A CENTRAL CALIFORNIA KELP FOREST 



Michael M. Singer^ 



ABSTRACT 



The diets and feeding morphology of juveniles of seven rockfish species (Scorpaenidae: Sebastes) were 

 investigated in a kelp forest at Stillwater Cove, Carmel Bay, CA. The seven species could be divided into 

 two groups, those which fed primarily on open water prey in the water column and those which fed on 

 substrate-associated prey. Substrate-associated prey were generally larger than open water prey and were 

 eaten by predators with relatively larger heads and mouths and shorter gill rakers. Comparison of juvenile 

 diets and foraging patterns with those of adults showed that both foraged in similar manners and in the 

 same general habitats. The absence of aggressive interactions within or among species and high intra- 

 specific variability of foraging patterns suggests that little interference or exploitative competition was 

 present. 



Most of the literature on rockfishes deals mainly with 

 aspects of either adult or larval biology (DeLacey 

 et al. 1964; Phillips 1964; Miller and Geibel 1973; 

 Westrheim 1975; Larson 1980a, b, c). Little of this 

 literature deals with the juvenile stage. Juvenile rock- 

 fishes often use nearshore kelp beds as nursery 

 grounds and, during certain times of the year, are 

 the most abundant members of the kelp-forest fish 

 community (Burge and Schultz 1973). The change 

 from pelagic life to a nearshore, reef-dwelling ex- 

 istence represents a major ecological transition. 

 With so many juvenile rockfish species co-occurring 

 in kelp forests, the potential for competitive inter- 

 action is great. Gaining an understanding of these 

 fishes' patterns of resource utilization (eg., food or 

 space) may be important in assessing the 

 mechanisms that affect their survival. 



The purpose of this study was threefold: 1) to in- 

 vestigate the food habits of juvenile rockfishes oc- 

 curring in a nearshore kelp forest, 2) to determine 

 the extent to which diet differed within and among 

 the various species present, and 3) to compare the 

 relationship between diet and morphology in juvenile 

 and adult forms. 



The juveniles of seven rockfish species were 

 studied. The adults of six of these species usually 

 occur nearshore, in association with rock reefs: blue 

 rockfish, S. mystinus; black rockfish, S. melanops; 

 olive rockfish, S. serranoides; copper rockfish, S. 

 caurinus; gopher rockfish, S. camatus; and kelp 



rockfish, S. atrovirens (Hallacher 1977; Roberts 

 1979). Adults of the seventh species, the canary rock- 

 fish, S. pinniger, occur deeper and usually offshore 

 (Miller and Lea 1972). For purposes of this study, 

 an individual was designated a juvenile upon first 

 appearance in the kelp forest, where fish were usual- 

 ly 25 to 30 mm SL. The fish used in this study 

 generally ranged from 30 to 70 mm SL. 



Sebastes mystinus and S. pinniger are among the 

 earliest species to recruit, usually appearing as early 

 as April. Sebastes mystinus usually occurs in the 

 water column above 6 m while S. pinniger occurs 

 on the substrate usually near sand/rock interfaces. 

 Sebastes caurinus begins recruiting around late 

 April or May and is found initially among kelp fronds 

 and near the surface Next to arrive are S. ser- 

 ranoides and S. melanops which first appear in May 

 and June Both these species occur mostly in the mid- 

 water within the kelp forest. Sebastes camatus usual- 

 ly begins to recruit in late June and July and, like 

 S. caurinus, is found initially among kelp fronds at 

 the surface Both S. caurinus and S. camatus move 

 down from the canopy and take positions near the 

 bottom after a couple of months (around June or July 

 for S. caurinus and late August or September for 

 S. camatus). The last of these species to recruit is 

 S. atrovirens, which begins to appear in late July 

 and August and occurs in the surface kelp canopy. 



METHODS AND MATERIALS 



^Moss Landing Marine Laboratories, Moss Landing, CA; present 

 address: VANTUNA Research Group, Occidental College, Moore 

 Laboratory of Zoology, 1600 Campus Road, Los Angeles, CA 9004L 



Manuscript accepted November 1984. 

 FISHERY BULLETIN: VOL. 83, NO. 4, 1985. 



Study Site 



All observations and samples were taken between 



531 



