FISHERY BULLETIN: VOL. 85, NO. 3 



sole and rex sole because these fishes were not 

 sufficiently abundant at the six additional sites. 



RESULTS 

 Prey Selection 



Throughout the diel cycle, the numerical pro- 

 portion of Capitella spp. in the diets of all three 

 fishes exceeded the proportion of these poly- 

 chaetes in the benthos (Table 1). Selection of 

 Capitella spp. was highly significant iP < 0.001) 

 during all four time periods for English sole and 

 rex sole, and during morning and night for Dover 

 sole. Selection was significant atP < 0.01 during 

 evening for Dover sole, but not significant 

 (P > 0.05) during afternoon for this species. 



Table 1. — Comparisons of proportions of Capitella spp. in fish 

 stomachs with the proportion in the benthos using a 2 x 2 contin- 

 gency test. "P < 0.01 , ***P < 0.001 , ns = P > 0.05 (experiment- 

 wise). 



Number of Capitella spp./Total number of prey 12 



Species Morning Afternoon Evening 



Night 



English 508/1, 464*" 425/1,029*** 1,072/1,596**" 1,904/2,592* 



sole (50) 



Dover 329/861 *** 

 sole (35) 



Rex 456/526*** 

 sole (16) 



(40) 



114/416 ns 

 (21) 



272/412*** 

 (18) 



(32) 



200/612* 

 (36) 



209/276* 

 (15) 



(56) 



218/461* 

 (36) 



603/671* 

 (19) 



■I Number of stomachs examined Is given In parentheses. 

 ^Proportion of Capitella spp. in the benthos was 904/3,51 7. 



Percent numerical contribution by Capitella 

 spp. to the total diet varied considerably among 

 the three fishes (Fig. 2). Rex sole showed the 

 greatest preference for these polychaetes, includ- 

 ing them in 66-90% of the diet throughout the diel 

 cycle. By contrast, Dover sole exhibited the least 

 preference for Capitella spp., including them in 

 only 27-47% of the diet. English sole showed mod- 

 erate preference for these polychaetes, including 

 them in 35-73% of the diet. Diel variation of feed- 

 ing intensity closely paralleled dietary contribu- 

 tions of Capitella spp. for English sole and rex 

 sole, with both variables peaking at night (Fig. 2). 

 For Dover sole, however, these two variables fol- 

 lowed substantially different diel trends, with 

 percent dietary contribution of Capitella spp. 

 reaching its maximum and feeding intensity 

 dropping to its minimum at night. 



Although the magnitudes of percent dietary 

 contribution by Capitella spp. differed among the 



three fishes, several similarities existed in the 

 diel variation of these values (Fig. 2). Minimum 

 dietary contributions were found during morning 

 (English sole) or afternoon (Dover sole and rex 

 sole), whereas maximum contributions were 

 found at night (all three fishes). 



< 



t- 

 o 



Q. 

 Cl 



•tr 



100- 

 80 

 60- 

 40- 

 20- 

 



English Sole 



56 

 32 |— 1 



50 ^° 



I- 100 

 80 

 60 

 40 

 20 

 



O 100-1 



O 80- 



Dover Sole 



m 

 cc 



H 

 Z 



o 



O 



< 



o 



cr 



LU 



z 



LU 



o 



cc 



LU 

 Q. 



D 



60- 



40- 



20- 



100 

 80- 

 60- 

 40- 

 20 

 



16 



Rex Sole 



15 

 18 



19 



Q 



100 



80 



60 



40 



20 







100 

 80 

 60 

 ■40 

 •20 

 



X 



o 

 < 



o 



I- 

 w 



DC 

 LU 

 Q. 



CC 

 Q. 



U- 

 O 



OC 

 UJ 



m 



3 

 Z 



Z 

 < 

 Q 

 LU 



MORNING EVENING 



AFTERNOON NIGHT 



SAMPLING PERIOD 



Figure 2. — Diel predation patterns of the target species. Num- 

 ber of stomachs examined is presented above each pair of bars. 



Prey Size Selection 



Median size of Capitella spp. in stomachs ex- 

 ceeded the median size of these polychaetes in the 

 benthos during all four time periods for English 

 sole and rex sole, and during morning, afternoon, 

 and night for Dover sole (Fig. 3). Median prey size 

 for Dover sole during evening was approximately 

 equal to median size of Capitella spp. in the ben- 

 thos. Size differences of Capitella spp. between 

 diets and the benthos were highly significant 

 iP < 0.001) during all four time periods for rex 

 sole, during morning, afternoon, and night for 

 English sole, and during morning and afternoon 

 for Dover sole. Size differences were significant at 



474 



