FISHERY BULLETIN: VOL. 74, NO. 4 



pnnctipinnis occur patchily in small mid-water 

 aggregations over the transect line and in much 

 larger aggregations along the outer margins of 

 the kelp bed. At night, however, they shelter in 

 holes throughout the entire study area. In fresh- 

 water lakes of Ontario at night, day-active fishes 

 move into shallow water where there is sufficient 

 cover for sheltering (Emery 1973), but in the 

 tropics, most day-active reef fishes shelter in holes 

 deep in the coral and so their exposed numbers 

 decrease at night (see Hobson 1974). 



The decrease in nocturnal abundance of fishes in 

 the transect area might have been caused by their 

 migrations to nearby areas of sand. Over coral 

 reefs, many of the more prominent fishes seen in 

 large stationary schools during the day are ac- 

 tually nocturnal species that leave the reef at dusk 

 (Hobson 1968). Among these are croakers (Sciaen- 

 idae), snappers (Lutjanidae), and grunts 

 (Pomadasyidae), which move to surrounding sand 

 flats to feed on their invertebrate prey during the 

 night (see papers by Hobson). However, we found 

 no evidence of a pronounced nocturnal migration 

 of fishes from reef and kelp to the surrounding 

 sand. Essentially all of the fishes observed during 

 the day were accounted for at one part or another 

 of the reef at night. On several occasions at night, 

 while swimming considerable distances over the 

 surrounding sand flats, we saw only species that 

 occur commonly at kelp-bed margins and do not 

 actively forage at night (e.g., Phanerodonfurcatus 

 and Damalichthys vacca), or that typically inhabit 

 sandy bottoms (e.g., the spotted cusk-eel Chilara 

 taylori, and various skates and rays). We have 

 occasionally seen relatively inactive schools of 

 black croaker, Oieilotrema saturnum, on the reef 

 during the day, and although we have not seen the 

 fish at night, it is possible that they migrate to 

 adjacent sandy areas to feed. Limbaugh (1961) 

 reported that they are most active at night. 



In a study of the night habits of coral reef fishes, 

 Starck and Davis (1966) noted that the feeding 

 times of reef fishes are closely related to the type 

 and activities of their prey. Microcarnivorous and 

 omnivorous fishes that browse and pick at sessile 

 organisms are generally active only during the 

 day. Mesocarnivorous fishes (i.e., those that feed 

 on larger motile invertebrate prey) are largely 

 nocturnal, because their prey (e.g., crustaceans) 

 are active and exposed at night. Planktivorous 

 fishes feed during both day and night, the noctur- 

 nal species having larger eyes than their diurnal 

 counterparts. Piscivorous fishes feed opportunis- 



712 



tically during the day and night, but are most 

 active at dawn and dusk when their prey fish are 

 exposed while moving to and from foraging and 

 sheltering areas. This feeding pattern has also 

 been observed in other tropical areas (Hiatt and 

 Strasburg 1960; Collette and Talbot 1972; Hobson 

 1974) and in freshwater lakes (Emery 1973). 



Kelp-bed fishes also tend to show this general 

 feeding pattern, though perhaps not so distinctly. 

 Small-mouthed microcarnivores that pick or graze 

 sessile invertebrates and hidden prey from off" the 

 bottom and other substrates are generally active 

 only during daylight hours. Such foragers, includ- 

 ing most of the surf perches, as well as Oxyjvlis 

 californica, Pimelometopon pulchrum, and Hyp- 

 sypops rnbicnndns, readily converge on urchins 

 broken open during the day, but completely ignore 

 such chum at night. 



Also as in the tropics, though less extensively so, 

 different planktivores feed in the mid-water zone 

 of kelp beds during the day and night. The most 

 visible daytime planktivores, Chromis punctipin- 

 nis and juvenile S. m.ystinus, often form mixed 

 aggregations of individuals that pick small zoo- 

 plankton from the incoming currents. At night, 

 neither was seen exposed outside its shelter, and 

 individuals collected by spear and later examined 

 had empty stomachs. Instead, the mid-water zone 

 is dominated at night by the large-eyed species, 

 Hyperprosopon argenteum, which darts about, 

 actively feeding throughout the water column. 

 Though we have little data on kelp-bed mesocar- 

 nivores, some, such as various rockfishes, Scor- 

 paenichthys marmoratus, and Ophiodon elonga- 

 tus, may feed at night. 



We emphasize the fact that many kelp-bed 

 fishes show considerable intraspecific variability 

 in vertical distribution and feeding activity. Al- 

 though a large majority of the population of C. 

 punctipinnis usually feeds in mid-water during 

 the day, e.g., a few individuals can usually be 

 found in holes. Likewise, a small proportion of the 

 day-sampled individuals of Embiotoca jacksoni 

 had empty foreguts even though the species is 

 strictly a diurnal forager. Even more variable is 

 the feeding schedule of Rhacochilus toxotes. Most 

 individuals probably have empty guts at any 

 daylight hour, although others are satiated. We 

 have observed that at any given time during the 

 day, most of these surfperch assemble as schools of 

 varying sizes just above the bottom or even in 

 mid-water (see also Alevizon 1975). However, a 

 lone individual may suddenly leave the school to 



