HOBSON: FEEDING RELATIONSHIPS OF FISHES 



Pomacentrus jenkinsi Jordan and Evermann 



This species is one of the more widespread and 

 numerous in Kona, especially in relatively quiet 

 water over coral and rocks. During the day, indi- 

 viduals are scattered among reef irregularities, 

 each seemingly associated with specific locations, 

 and here they pick at coral and rock surfaces. At 

 night they hover under cover, remaining alert but 

 relatively inactive until shortly after first light, 

 when diurnal activity is resumed. 



Twenty-two specimens (89: 80-100 mm) were 

 collected during day and night. All 12 that were 

 speared as they swam close to the reef during 

 midday were full of food, much of it fresh, whereas 

 of 5 that were speared in reef crevices at night 

 (between 4 and 5 h after last evening light), the 

 stomachs of 3 were empty and those of the other 2 

 contained only a few well-digested, unidentified 

 fragments. Finally, of five active individuals that 

 were collected during morning twilight and dur- 

 ing the first 30 min after sunrise, two were empty, 

 and three contained in their stomachs a few fresh 

 fragments that appeared to have been recently 

 ingested. The 15 specimens that contained at least 

 some fresh material had consumed the items 

 listed in Table 39. 



The amorphous organic fragments that consti- 

 tuted the bulk of the gut contents in this fish were 

 in part items that had been digested beyond rec- 

 ognition; however, most of this material appeared 

 to be detritus — organic deposits — that had been 

 scraped from the reef. Gosline and Brock (1960) 

 noted that P.jenkinsi inhabits quiet water, where 

 it feeds on algae, and perhaps detritus. Hiatt and 

 Strasburg (1960) also found this fish in quiet 

 water in the Marshall Islands and reported it to be 

 primarily a herbivore that feeds occasionally on 

 small fishes. 



CONCLUSION. — Pomacentrus jenkinsi is a 

 diurnal omnivore that takes mostly organic de- 

 tritus, algae, and small animals from reef sur- 

 faces. 



Abiidefdiif sindonis (Jordan and Evermann) 



This damselfish occurs where basalt boulders 

 are swept by a strong surge. Activity is limited to 

 daylight; at night it remains under cover among 

 the rocks. 



All five specimens (91: 81-102 mm) were 

 speared during the day, and their guts were full of 

 the material listed in Table 40, much of it fresh. 

 The amorphous organic fragments, the major food 

 item, probably are largely detritus from the reef, 

 such as is also taken by Pomacentrus jenkinsi, 

 discussed above. Where a strong surge sweeps the 

 boulder habitat, A. sindonis replaces P.jenkinsi 

 in depths shallower than about 3 m. 



Gosline and Brock ( 1960) noted that A. sindonis 

 seems restricted to surge areas among lava rocks 

 and appears to be omnivorous. 



CONCLUSION. — Ahudefduf sindonis is a diur- 

 nal omnivore that takes mostly organic detritus, 

 algae, and small animals from the substratum. 



Abudefduf sordidus (Forskal) — kiipipi 



Although juveniles of A. sordidus are promi- 

 nent in tide pools, the adults, which are the largest 

 of the Hawaiian pomacentrids, seem to occur only 

 where a precipitous basalt reef face confronts a 

 prevailing swell. In this situation large individu- 

 als of this species are fairly numerous among 

 rocky crevices and close to boulders at the base of 

 the reef. Generally a solitary fish, A. sordidus is 



Table 39. — Food of Pomacentrus jenkinsi. 



979 



