FISHERY BULLETIN: VOL. 73, NO. 4 



o = bites • = grids 



3 

 C 



to 





x> 



E 



3 



240 



120 



c 

 E 

 in 



(/) 

 to 



o 





en 



E 



3 



0600 



1200 



1800 



Time 



2400 



0600 



Figure 3.-Feeding and swimming activity of; top, l<elp perch; 

 middle, white seaperch; and bottom, senorita. Open circles are 

 feeding rates observed in the field and standardized as bites per 

 minute (fish do not feed at night); solid circles are swimming 

 rates observed in a laboratory tank and measured as grid-line 

 crossings per 5-min period. Each point represents the mean value 

 for (n) individuals (feeding rates) or five or six individuals 

 (swimming rates) observed for a 2-h interval. 



Swimming Rate 



Showing little if any spatial or temporal pat- 

 tern, the two perches swam sporadically 

 throughout the experimental tank during the day 

 and night (Figure 3). Kelp perch swam in spurts 

 and were slightly more active during the day than 

 at night; white seaperch were most active at dawn; 

 and neither species showed any marked change at 

 dusk. The apparent increase in kelp-perch activity 

 at dawn reflected intense swimming by one in- 

 dividual, whose exclusion from the sum would 

 lower the mean species rate to 38 grid-line cross- 

 ings per 5-min period, about the same as for white 

 seaperch. 



In the field during the day, white seaperch swam 

 more continuously in mid-water and near the bot- 

 tom than did kelp perch, which tended to hover 



camouflaged among the kelp canopy and only oc- 

 casionally darted in and out. At night, white 

 seaperch were occasionally seen drifting slowly in 

 mid- water or over the bottom, while kelp perch 

 tended to hang motionlessly among the kelp stipes 

 or even in open water. Kelp perch, especially, were 

 quiescent at night and easily caught with a small 

 hand net then. 



Senoritas swam most actively during the morn- 

 ing, then progressively slower throughout the day 

 before finally burying themselves in the sand for 

 the night (Figure 3). Beginning 20 min before 

 sunset during one 24-h trial, a fish that was ob- 

 served continuously first swam actively 

 throughout the tank, then more restrictively over 

 the sandy area. Finally after swimming in smaller 

 circles about 4-6 cm off the bottom, it turned on its 

 side and, with a few flicks of its caudal fin, 

 proceeded head first into the sand. This entire 

 episode lasted about 10 min, after which the area 

 became dark. Observations by flashlight showed 

 that the fish had buried itself completely, as had 

 three others that accompanied the fish during the 

 trial. Beginning 5 min after sunrise, the four fish 

 emerged within 12 min. Two first stuck their heads 

 above the sand to expose their pectoral fins, then 

 after a short pause, swam out and milled about in 

 small circles. The second pair emerged in a single 

 movement to join the others in a small school, 

 which soon moved throughout the tank. Of the 

 total of seven fish observed in two trials, all buried 

 themselves but one, which lay motionlessly 

 against some bricks and assumed a mottled color 

 pattern. 



In the field, three fish observed on separate oc- 

 casions over a reef about 10 m deep showed 

 settling and burying behavior like that of the 

 experimental animals, although they did not leave 

 to seek a surrounding area of sand flat. Instead, 

 they left a loose aggregation of fish before dusk to 

 remain near the rocky substrate. They gradually 

 restricted their spheres of activity to a small cir- 

 cular area above depressions filled with coarse 

 sand and rubble. Just before sunset when visibility 

 had decreased to about 3 m, the fish became 

 hypersensitive to a diver's light and would dart 

 away quickly when illuminated. About 15 min 

 after sunset, the fish buried themselves in the 

 depressions, first rolling on their sides and then 

 swimming headfirst into the loose substrate. 

 Gentle excavations caused the fish, which were 

 probably buried within the upper 8 cm, to flee 

 quickly. In more than 150 h of scuba diving at 



822 



