HOBSON: FEEDING RELATIONSHIPS OF FISHES 



it fresh. Similarly, of 12 individuals collected as 

 they swam close to the reef during afternoons, 

 only 1 had an empty stomach, whereas the other 

 11 contained prey in varying stages of digestion, 

 some of it fresh. Finally, of four specimens speared 

 at night (between 4 and 5 h after sunset) the 

 stomach of one was empty, but the other three 

 contained prey in varying stages of digestion, 

 some of it fresh. 



These data indicate that P. bifasciatus feeds 

 regularly during both day and night. Recognizing 

 that the contrasting conditions under which it 

 hunts may be reflected in the composition of its 

 diet, I attempted to distinguish prey that had been 

 taken by day from that taken at night. Although, 

 undoubtedly there is overlap, generally specimens 

 collected during the night and early morning 

 should contain mostly prey captured after dark, 

 whereas specimens taken during afternoons 

 should contain mostly prey taken in daylight. 



Thus, the 12 P. bifasciatus taken during the 

 night and early morning with identifiable mate- 

 rial in their stomachs presumably represent most- 

 ly nocturnal feeding. Items in these individuals 

 are listed in Table 26. Using the same rationale, 

 diurnal feeding presumably is reflected in the 11 

 P. bifasciatus collected with identifiable material 

 in their stomachs during afternoons. Items in 

 these individuals are listed in Table 26. 



Although xanthid crabs are the major prey day 

 and night, they assume greater relative impor- 



tance in daylight, as do caridean shrimps. Xan- 

 thids and carideans are largely under cover in day- 

 light, where they may be especially vulnerable to 

 this predator's probing actions. Crab megalops be- 

 come increasingly important to this goatfish at 

 night, but the circumstances surrounding their 

 capture remain uncertain; megalops are the major 

 prey of many nocturnal planktivores, such as 

 Myripristis spp. (see accounts for these species, 

 above), but are also taken day and night by pred- 

 ators like certain goatfishes that probe the sea 

 floor. 



Based on the above data, fishes seem to be more 

 available as prey to P. bifasciatus at night. Prey 

 fishes that could be identified were blennies and 

 pomacentrids, which are diurnal fishes that take 

 cover after dark. Apparently P. bifasciatus is 

 adapted to capture these resting diurnal fishes at 

 night, but is less effective in capturing the fishes 

 that are under cover during daylight. 



CONCLUSION. — Parupeneus bifasciatus 

 hunts prey on the reef during both day and night. 

 Adult crabs and shrimps are more important as 

 prey during the day than at night, whereas the 

 reverse is true of fishes and crab megalops. 



Parupeneus porphyreus (Jenkins) — kumu 



This is the most numerous goatfish on some 

 Hawaiian reefs (Gosline and Brock, 1960), but 



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