FISHERY BULLETIN: VOL. 79, NO. 1 



Figure 12. — Pleuronichthys coenosus, which feeds day and night, largely on sand-dwelling polychaetes, has eyes on either side of a 

 bony ridge set almost as if in a turret. This arrangement increases its ability to scan the surrounding seafloor for prey and threatening 

 predators. 



is based on observations by Hobson 1965, 1968a, 

 1974; Starck and Davis 1966; and others) involves 

 species (often referred to as coral-reef fishes) from 

 a variety of contiguous habitats. A comparison of 

 diurnal and nocturnal behavior requires a mul- 

 tihabitat view because so many fishes move from 

 one habitat to another between day and night. 



The general scene in Californian nearshore 

 habitats differs dramatically between day and 

 night. A major aspect of this difference is the sharp 

 drop in observed activity among fishes on reefs 

 after dark. Describing an "aura of desolation . . ." in 

 the "notably lackluster night life, . . ." Ebeling and 

 Bray (1976) considered this feature of kelp forests 

 to be in contrast to tropical reefs. But on tropical 

 reefs, too, one notes less activity at night than 

 during the day (e.g., Starck and Schroeder 1965). 

 Nevertheless, there may be an especially pro- 

 nounced difference where Ebeling and Bray 

 studied, because the relative dearth of nocturnal 

 activities there led them to conclude: "...in kelp 

 beds there is no broad replacement for the 'day 



shift' of fishes at night." In particular, they re- 

 ported an absence of fishes that move from day- 

 time assemblages on reefs to nocturnal feeding 

 grounds on adjacent sand, and also to there being 

 relatively few nocturnal planktivores. But the 

 situation they described is unlike that which pre- 

 vails in the more southerly waters around Santa 

 Catalina, where many species are most active at 

 night. Following a pattern widespread in the 

 tropics, for example, Xenistius californiensis , 

 Umbrina roncador, Seriphus politus, and Hyper- 

 prosopon argenteum (to mention species consid- 

 ered in this report) are relatively inactive in 

 schools near shore, reefs, or kelp forests by day, 

 and disperse over feeding grounds elsewhere at 

 night. It may be significant, however, that with the 

 exception of//, argenteum, these are species with 

 close tropical affinities (Table 4). In contrasting 

 the relative absence of nocturnal planktivores at 

 their Santa Barbara study site, vdth the many 

 such forms at Santa Catalina (as reported by Hob- 

 son and Chess 1976), Ebeling and Bray suggested 



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