FISHERY BULLETIN: VOL. 74, NO. 4 



and senorita, Oxyjulis californica (by Bray and 

 Ebeling 1975); and the horn shark, Heterodontus 

 francisci, and swell shark, Cephaloscy Ilium ven- 

 triosum (by Nelson and Johnson 1970). More 

 recently, Hobson and Chess (1976) presented more 

 comprehensive comparisons of the day and night 

 feeding activities of fish off Santa Catalina Island: 

 in particular, of the blacksmith, Chromis punc- 

 tipinnis; the walleye surfperch, Hyperprosopon 

 argenteum; the kelp rockfish, Sebastes atroviretis; 

 the olive rockfish, S. serranoides; the queenfish, 

 Seriphus politus; and the salema, Xenistius 

 californiensis, as well as some of the others 

 mentioned above. Therefore, we initiated a com- 

 parative day and night survey of the fishes in- 

 habiting an area of reef and kelp off Santa Bar- 

 bara, Calif., to see if the fish community under- 

 goes a substantial diel change in its composition, 

 vertical distribution, and activity. 



METHODS 



Naples Reef is a large rocky outcrop located 24 

 km west of Santa Barbara (lat. 34°25'N, long. 

 119°57'W). The reef measures 275 m by 80 m (2.2 

 hectares) and lies 1.6 km offshore. The substratum 

 consists of a series of sandstone rills and ridges 

 that run parallel to the coast. Depths across the 

 reef average 8 to 10 m, although some prominences 

 project to within 5 m of the surface. The bottom 

 surrounding the reef is 16 to 20 m deep and is 

 comprised of sand with rocky outcrops inshore, or 

 sand and cobbles offshore. The assemblage of plant 

 and animal life on and about the reef is among the 

 richest along the Santa Barbara coast. Giant kelp 

 (Macrocystis) is always present on the reef, al- 

 though kelp densities fluctuated throughout the 

 study period. Temperatures along the top of the 

 reef ranged from 11°C in the spring to 19°C in the 

 fall. Underwater visibility averaged 5 m at the 

 transect line. 



A transect line consisting of two 40-m segments 

 was staked along either side, shoreward and 

 seaward, of a high-relief ridge with a crest at 6 m. 

 Day and night counts of fishes along the line were 

 made by scuba divers. For each day-night pair of 

 samples, we counted fish within 2 m on either side 

 of the line. To minimize the effect of nondiel 

 fluctuations on our observations, we always made 

 the night transect member of a pair within 12 h of 

 the day transect. A special effort was made to 

 insure that the night counts of fish were made 

 throughout approximately the same reef area and 



overlying volume of water as were the day counts. 

 Powerful 10-cell underwater hand lights, fitted 

 with reflectors to illuminate the data sheets, were 

 used intermittently during the day to inspect 

 holes, and used continuously throughout the night 

 dives. 



We evaluated the diel activities of fish species by 

 observing the fishes' vertical distribution and 

 feeding habits. During the transects, fish sight- 

 ings were tallied in separate columns on our plastic 

 data sheets according to the zone in which each 

 individual was observed (Table 1). 



The use of dive lights at night may have at- 

 tracted or repelled fish depending on the species 

 and/or altered their state of activity. Yet fishes 

 normally inactive at night did not seem to be 

 affected by brief exposures to dive lights. Species 

 normally active at night responded in various 

 ways, from showing hyperactivity to apparent 

 immobilization. Other nighttime observations of 

 reef fishes off California (Nelson and Johnson 

 1970) and in tropical waters (Hobson 1965; Starck 

 and Davis 1966; Smith and Tyler 1972) also in- 

 dicate that night-active fishes often respond un- 

 predictably to artificial illumination. 



Day and night differences in the feeding habits 

 of many species were inferred either from direct 

 observations of foragers or from changes in the 

 fishes' vertical distribution and activity level (i.e., 

 whether the fish were exposed and responsive to 

 our presence or sheltered and unresponsive). We 

 feel that such observations of fish activity by 

 themselves were sufficient to distinguish feeding 

 from nonfeeding periods for many of the more 

 prominent species. However, such observations 

 proved to be inadequate indicators of foraging 

 activity for surfperches (Embiotocidae), which 

 comprise the most abundant and diverse foraging 

 guild of the fishes on Naples Reef. To test for diel 

 differences in feeding activity of surfperches, 

 therefore, we speared during all hours of day and 

 night approximately 400 adults of the five common 

 demersal species: the black perch, Emhiotoca 

 jacksoni (median standard length 195 mm, range 



Table 1.— Zones of vertical orientation in which fish were 

 observed along a transect line 



Zone 



Extent of zone 



IV Mid-water 



III Suprabenthic 

 II Bottom 



I Shelter 



Greater than 1.0 m above the bottom, in open 



water and/or near kelp stipes 

 Within 1.0 m of the bottom 

 In physical contact with the bottom yet 



exposed 

 In holes, crevices, or under ledges 



704 



