LOVE and EBELING: FOOD AND HABITAT OF THREE FISHES 



sence of regular sport fishing in particular areas 

 may condition or disturb the fish fauna (Quast 

 1968b, c). Quast inferred that kelp bass move 

 quickly from bare sites into more heavily foliaged, 

 favored habitats as previous inhabitants are re- 

 moved by fishing. In the present study, however, 

 the influence of sport fishing was minimal because 

 large partyboats visited Naples Reef infrequently 

 from 1970 to 1973 (due to the erratic state of the 

 Santa Barbara sport fishery then), and we made 

 special effort to avoid the few skiff fishermen. 



Nonetheless, our samples may be biased in 

 other ways. Quast ( 1968b) listed such sport-diving 

 activities as shellfish gathering, which disturbs 

 the bottom, and spearfishing among factors that 

 condition fish behavior. Although we designed our 

 sampling regime to minimize most hazards, we 

 admit that spearing may induce wariness, espe- 

 cially in kelp bass. Hence, our method of spearing 

 fishes as they were encountered may have selected 

 certain individuals by virtue of their size or condi- 

 tion. 



Perhaps even more importantly, angling olive 

 rockfish from One-Mile Reef, even with unbaited 

 lures, may have selected hungrier or weakened 

 individuals with empty stomachs. Randall (1967) 

 noted that fish angled in tropical areas often have 

 empty stomachs and some regurgitate their meal 

 during the fight. Our One-Mile Reef specimens did 

 in fact average less stomach fullness than did 

 Naples Reef fish. But since they averaged greater 

 intestinal fullness, they probably had been feed- 

 ing normally. 



Our sampling may reflect some temporal bias. 

 We collected most fish near midday when feeding 

 may slacken. In the tropics, larger generalized 

 carnivores feed mainly at dawn and dusk (e.g., 

 Hobson 1974) or even at night if there is sufficient 

 light (Randall and Brock 1960). In a study of 

 kelp-bed fishes off Santa Catalina Island (ca. 160 

 km south of Santa Barbara) Hobson and Chess 

 (1976) inferred that juvenile olive rockfish in the 

 65- to 157-mm SL range feed mostly at night. Quast 

 (1968c) found that only 10-50*7^ of specimens of the 

 three species collected during the day off San 

 Diego contained food. In the present study, how- 

 ever, most specimens contained substantial 

 amounts of food in their stomachs, which were 

 often more packed than their intestines. And indi- 

 viduals were often seen feeding during the day but 

 seldom at night, when they usually sit quietly on 

 the bottom or hide in holes (Ebeling and Bray 

 1976). Similarly off central California, blue 



rockfish, at least, are typically active during the 

 day (Gotshall et al. 1965; Miller and Geibel 1973). 



Evidence for Switch Feeding 



Are the three species indeed switch-feeding 

 predators? They are certainly equipped to switch 

 from large to small prey. All have large mouths for 

 engulfing big items, yet have protrusible jaws and 

 well-developed gill rakers for selecting and keep- 

 ing small ones. 



In general, switch feeders show relatively weak 

 preference for alternative prey and readily take 

 the more abundant or otherwise more available 

 kind (Murdoch et al. 1975). Switching mech- 

 anisms may involve avoiding a previous prey or 

 selecting a new one ( perhaps by acquiring a search 

 image), spending more time in the area occupied 

 by the new prey, or improving capture technique 

 as the new prey becomes more abundant ( Murdoch 

 et al. 1975). Any of these mechanisms should 

 make individual fish specialize. We could not com- 

 pare diets with prey density, which we did not 

 measure. Indirectly, then, we wanted to see if a 

 relatively large proportion of fish contain mostly 

 one of an array of alternative kinds of prey. 



This seems to be the case. A fish usually con- 

 tained mostly one and not a combination of prey 

 types. Moreover, its stomach and intestinal con- 

 tents usually matched, implying that it had fed on 

 the particular prey type for a few hours (Windell 

 1971). 



Also, the percentage offish (167c) containing a 

 single dominant food item is relatively large. It 

 exceeds the estimated percentage (55%) for 

 picker-type microcarnivores — small-bodied fishes 

 with pointed, specialized mouths — which also in- 

 habit the midwaters of the kelp bed (original data 

 from Bray and Ebeling 1975). And it greatly ex- 

 ceeds the small percentage (139^) for demersal 

 microcarnivores — somewhat larger fishes (Em- 

 biotocidae) with small mouths and fleshy lips — 

 which usually inhabit the waters just above the 

 reef surface (Ebeling and D. Laur in prep.). With 

 food breadths exceeding 4.0, demersal microcar- 

 nivores eat a diverse array of prey, but all of the 

 substrate-oriented type, and seldom one item at a 

 time. Fryer (1959) concluded that in Lake Nyasa 

 (Malawi), Africa, switch feeding is easy for more 

 generalized predatory fishes, but is difficult or im- 

 possible for many of the more specialized species. 



If switching is a simple functional response (in 

 the sense of Solomon 1949) to more of a particular 



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