FISHERY BULLETIN: VOL. 72, NO. 4 



Table 10. — Food of Holocentrus sammara. 



2.2). Three contained unidentified crustacean 

 fragments (mean percent of diet volume: 24; rank- 

 ing index: 14.4). 



CONCLUSION. — Holocenti'us spinifera is a 

 nocturnal predator that feeds mostly on benthic 

 crustaceans, especially caridean shrimps and 

 xanthid crabs. 



Holocentrus Here Cuvier 



This relatively numerous holocentrid is mostly 

 secreted in reef caves during the day, but after 

 dark sw^ims in exposed locations at depths below 5 

 m, especially along reef ledges. It emerges from 

 cover after last evening light and regains shelter 

 before, or at, first morning light. Like//, sammara 

 and //. spinifera, above, //. tiere has distinctive 

 diurnal and nocturnal color patterns (Figure 12a 

 and b). 



Fifteen specimens (141: 67-160 mm) were 

 speared as they swam in the open at night, or just 

 after they had returned to shelter at daybreak: 1 1 

 of these had food in their stomachs; 3 taken within 

 4 h after sunset were empty — apparently their 

 nocturnal hunt had not yet been successful; 1 

 taken under a ledge during morning twilight also 

 had an empty gut, indicating that it had passed 

 the night without feeding. Items in the 11 speci- 

 mens containing identifiable material are listed 

 in Table 11. 



CONCLUSION.— //o/ocen^rws tiere is a noc- 

 turnal predator that feeds mostly on benthic crus- 

 taceans, especially xanthid crabs and caridean 

 shrimps. 



Holocentrus xantherijthrus Jordan and Ever- 

 mann 



During the day this relatively small holocentrid 

 aggregates in crevices and under overhangs of 

 basalt reefs (Figure 13) in water deeper than 6 m, 

 but especially below 20 m. After dark it ranges out 



from this shelter and into the surrounding areas, 

 where solitary individuals are active close to rock, 

 coral, or pockets of sand. By first morning light it 

 has returned to its daytime retreats. At night this 

 fish has prominent white vertical markings on its 

 body like those illustrated for //. tiere (Figure 

 12b). 



Of the 29 individuals (106: 88-123 mm) speared 

 at different times of day and night, the stomachs of 

 all 15 that were active in exposed locations on the 

 reef during the 2 h immediately before daybreak, 

 or were under reef shelter within an hour of sun- 

 rise, contained prey in varying stages of digestion, 

 whereas the stomachs of all 11 taken from reef 

 crevices during afternoons were empty. The re- 

 maining three were taken within 2 h after last 

 light, shortly after they had begun their nightly 

 foraging, and although one was empty, the other 

 two contained fresh prey. Items in the 17 speci- 

 mens that contained identifiable material are 

 listed in Table 12. 



CONCLUSION. — Holocentrus xantherythrus is 

 a nocturnal predator that feeds mostly on benthic 

 crustaceans, although some free-swimming crus- 

 taceans are also taken close to the bottom. 



Holocentrus diadema Lacepede 



After dark, many individuals of this relatively 

 small squirrelfish swim close to the sea floor where 

 coral growth is rich at depths below 3 to 4 m. 

 Holocentrus diadema is secretive by day, gener- 

 ally remaining out of sight within the many nar- 

 row interstices of its coral-rich habitat, but is oc- 

 casionally glimpsed in the shadows at the base of 

 coral heads. Generally, it does not leave its day- 

 time shelter until after last evening light, and 

 returns to cover before or at first morning light. At 

 night this fish, like //. xantherythrus, above, has 

 prominent white vertical markings on its body 

 that are similar to those on the nocturnally active 

 //. tiere (Figure 12b). 



934 



