FISHERY BULLETIN: VOL. 79, NO. 3 



year (of about 2-3 cm TL) first appeared inshore off 

 Avila during March and April. At this stage, they 

 were particularly common under the kelp canopy 

 and over very shallow, protected rocky reefs (occa- 

 sionally in the lower intertidal zone). Although 

 they were not directly observed there, young-of- 

 the-year probably also occur on reefs somewhat 

 farther offshore (depth 20-50 m), since they were 

 often found in the stomachs of resident rockfish in 

 these habitats. 



Food Habits 



Olive rockfish were found to be primarily mid- 

 water predators of nekton (Table 5). Very impor- 

 tant among its prey were small fishes, including 

 blue rockfish; young olive rockfish; pipefish, 

 Syngnathus sp.; shiner perch, Cymatogaster 

 aggregata; kelp gunnel, Ulvicola sanctaerosae; 

 northern anchovy, Engraulis mordax; topsmelt, 

 Atherinops affinis; and cottids. Another important 

 nektonic prey was the squid Loligo opalescens. 

 Among planktonic prey, small crustaceans ( partic- 

 ularly crab megalops larvae), tunicates (Oikop- 

 leura sp., Doliolium sp.), euphausids, fish larvae, 

 and polychaetes were commonly eaten. Among 

 substrate-oriented prey, octopus was the most 

 important food item, followed by gammarid am- 



phipods, isopod Idothea sp., and other small 

 crustaceans. 



As olive rockfish grow, their food habits change. 

 Previous studies (Quast 1968b; Hobson and Chess 

 1976; Love and Ebeling 1978) have shown juvenile 

 olive rockfish to be primarily midwater feeders, 

 actively swimming after such forms as poly- 

 chaetes, megalops larvae, mysids, and small 

 fish. In the present study, though planktonic 

 forms were important for individuals of all size 

 classes, nektonic animals, primarily fish and 

 squid, assumed dominance in the diet as the fish 

 grew larger (Table 6). Plankton consumed by 

 smaller individuals included a wide variety of 

 small and large crustaceans, fish larvae, and 

 polychaetes. For larger fish, plankton consump- 

 tion was essentially limited to large items, such as 

 euphausids, tunicates, and polychaetes. Nekton 



Table 6. — Percentage occurrence of prey types in stomachs 

 of four size classes (total length) of olive rockfish from Avila, 

 Calif. Probabilities determined by 2 x 2 contingency G-test 

 (Sokal and Rohlf 1969). 



*P=s0.05, "P«0.01. 



Table 5. — Percentage total volume and frequency of occurrence of 17 food items in stomachs of olive rockfish off Avila, Calif Olive 

 rockfish are divided into 10.0 cm TL size groups. Food items are grouped by behavior and habitat. 



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