EBELING and BRAY: ACTIVITY OF REEF FISHES 



feed rapidly over the bottom for several minutes 

 before rejoining the same or another school of 

 lazily swimming, nonfeeding fish. But we do not 

 know yet if any particular individuals tend to feed 

 in this sporadic manner during the day to a 

 greater extent than do most others which may 

 feed more consistently during the night. Hobson 

 (1971, 1976) stressed the probably widespread 

 occurrence of individual variation in the tendency 

 of fishes to "clean" ectoparasites from larger host 

 species. Specifically, Hobson (1976) observed that 

 even though cleaning is not considered to be 

 characteristic of the rock wrasse, Halichoeres 

 semicinctus, this feeding mode was repeatedly a 

 major activity in what was probably the same 

 individual. Thus, as far as fish activities are 

 concerned, the behavior of an individual is not 

 always predictable from the general characteris- 

 tics of its species. 



Temperate-Tropical Differences 



Some phenomena that characterize the day- 

 night change in activities of fishes inhabiting 

 tropical coral reefs appear less well developed or 

 absent in the activity cycles of the Santa Barbara 

 kelp-bed fishes. For one thing, no kelp-bed species 

 that we observed forms inactive schools over the 

 reef during the day and disperses elsewhere to 

 feed at night, as do snappers and grunts in tropical 

 systems. Another noticeable lack in the kelp 

 forests is the widespread replacement of daytime 

 mid-water planktivores by nighttime counter- 

 parts. In tropical areas, this replacement involves 

 more species and, to some extent, occurs vertically: 

 at night, the diurnal planktivores (a few 

 pomacentrids, the unusual labrid Clepticus, etc.) 

 take refuge in reefs that had provided shelter for 

 the nocturnal planktivores (some holocentrids, 

 apogonids, priacanthids, etc.) during the day 

 (Hobson 1968, 1972; Collette and Talbot 1972). In 

 our kelp-bed system at Naples Reef, however, the 

 only noticeable replacement of the abundant 

 daytime mid-water planktivores is Hyperprosopon 

 argenteum, which, moreover, is probably a "hor- 

 izontal replacement" from inshore areas. In this 

 system, the only common fish that shelters during 

 the day and may emerge at night is Cephaloscyl- 

 lium ventriosum, a rather slow-moving piscivore 

 that probably eats sheltering or inactive prey 

 (Nelson and Johnson 1970). The cryptic demersal 

 mesocarnivores (i.e., carnivores that feed on 

 medium-sized prey, e.g., rockfishes, Scorpaen- 



ichthys marmoratus, etc.) may shelter either day 

 or night between feeding bouts. 



However, feeding on plankton at night may be 

 more widespread in areas farther south. Hobson 

 and Chess (1976) concluded that several species eat 

 plankton at night off Santa Catalina Island. 

 Though they are relatively rare at Naples Reef, for 

 example, individuals of Sebastes atrovirens and 

 larger juveniles of S. serranoides are important 

 mid-water planktivores at night in kelp beds off 

 Santa Catalina. Also, Xenistivs californiensis 

 picks plankton in the relatively clear waters 

 around this island, but this species does not com- 

 monly occur as far north as Santa Barbara. Naples 

 Reef is located just south of a faunal boundary at 

 Point Conception (cf. Hubbs 1960; Quast 1968; 

 Briggs 1974). Also, our mainland assemblage differs 

 noticeably from nearby insular communities 

 (Ebeling et al. unpubl. data). Nonetheless, it is 

 reassuring to find that many of our results parallel 

 those of Hobson and Chess. 



Figure 2 summarizes the day-night distribu- 

 tions of kelp-bed fishes from an evolutionary point 

 of view. Fish are depicted as being distributed 

 vertically, based on their proportionate abun- 

 dances in each of the four zones, from the mid- 

 water zone to the shelter zone, and as comprising 

 four ecological groups, based on their habits and 

 phylogenetic origins. Belonging to taxa with 

 temperate origins, all species in group A are 

 demersal species of the bottom-habitat group, 

 which generally move but little from their perches 

 on the bottom during the day or night (see Table 4, 

 \h = 0.42). Groups B, C, and D are composed of 

 more active species that commonly occur in the 

 suprabenthic zone and in mid-water during the 

 day, but there the similarity ends. Also with 

 temperate origins, species in group B are large- 

 mouthed generalized predators, which can switch 

 from plankton to larger prey including small fishes 

 as the occasion arises (Love 1974), and simply 

 descend to rest on the bottom at night {Ih = 1.92). 

 Group C and D species are small-mouthed 

 microcarnivores of mixed origins, which either 

 forage over the substrate or pick plankton from 

 mid-water. Group C fishes are all surfperches with 

 a common temperate origin, whose day-night 

 change in vertical position is relatively slight 

 {ih ^ 0.22), and whose nocturnal behavior is rela- 

 tively unspecialized. in that the fish simply slow 

 down over the bottom and do not generally seek 

 shelter in holes and crevices. But in contrast with 

 all the others, group D fishes appear to be rela- 



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