HOBSON: FEEDING RELATIONSHIPS OF FISHES 



Table 22. — Food of Monotaxis grandoculis. 



CONCLUSION. — Monotaxis grandoculis is a 

 nocturnal predator that feeds on benthic inverte- 

 brates, most of them heavily shelled. 



General Remarks on Porgies 



Porgies are closely related to the snappers, most 

 of which seem to be mainly nocturnal. Neverthe- 

 less, porgies have been reported as diurnal, for 

 example species of Archosargus, Diplodus, and 

 Calamus in the tropical Atlantic (Randall, 1967). 

 Still, Starck and Davis (1966) recognized that 

 species of Calamus in Florida may also feed at 

 night. Diurnal habits in porgies may be attributed 

 to their habit of excavating buried prey, which 

 makes available to them certain nocturnal forms 

 that have concealed themselves in the sand during 

 daylight. 



Family Mullidae: goatfishes 



Mulloidichthys auriflamma (Forskal) — weke'ula 



During the day this goatfish, which is relatively 

 numerous in Kona, hovers in schools above the 

 reef, or (occasionally) under ledges. Individuals 

 recognized by distinguishing marks occurred in 

 schools at the same locations each day, even 

 though these schools disperse at nightfall. After 

 dark, solitary or in small groups, this species 

 probes with its barbels in the sandy areas adjacent 

 to the reef, and in some of the larger sand patches 

 on the reef. When illuminated by a diving light at 

 night, it often shows a deep reddish hue that seems 

 to be a reaction to the light, not a nocturnal colora- 

 tion. 



Of the 22 individuals (170: 110-235 mm) 

 speared during day and night, all 12 collected from 

 schools during the afternoon were either empty or 



contained only well-digested fragments, whereas 

 of the 10 collected at night (later than 3 h after 

 sunset and before sunrise), all contained food, in- 

 cluding fresh material, as listed in Table 23. 



Thus my observations concur with those of Gos- 

 line and Brock (1960), who reported that M. 

 auriflamma does not feed during the day, but in- 

 stead schools quietly in certain established areas 

 and then disperses to forage at night. 



Although crab megalops, a primary food, are a 

 major element of the plankton, most of those cap- 

 tured by this goatfish probably were taken from 

 the sand. 



CONCLUSION.^Ma//oj(iicA^y's auriflamma is 

 a nocturnal predator that feeds on invertebrates 

 that live in the sand. 



Mulloidichthys samoensis (Giinther) — 

 tveke 'a' a 



This goatfish, widespread in Kona, often hovers 

 in quiet schools over the reef during the day, 

 where it looks much like M. auriflamma, above. 

 Although M. samoensis is a more elongated fish, 

 the two must be seen together before this distinc- 

 tion is obvious. Sometimes the two species school 

 together, but more often they are segregated. Fre- 

 quently instead of schooling during the day, M. 

 samoensis, but not M. auriflamma, moves as soli- 

 tary individuals or in small groups over sand 

 patches on the reef, and there actively probes with 

 its barbels in the sediment. These active individu- 

 als have a color pattern distinct from that of rela- 

 tively inactive conspecifics in schools. When 

 schooling, M. samoensis has a prominent yellow 

 stripe running from eye to tail along its upper 

 sides, as does M. auriflamma in similar schools 

 (Figure 23a); however, this stripe is not present (or  

 at least is indistinct) when M. samoensis actively 



957 



