HOBSON: FEEDING RELATIONSHIPS OF FISHES 



and coral interstices during the day, but emerges 

 and aggregates in the lower levels of the water 

 column, above the reef, about 30 min after sunset. 

 After remaining active during the night, it re- 

 turns to its daytime shelter on the reef about 30 

 min before sunrise (Hobson, 1972, as M. 

 multiradiatus) . When this fish is under cover dur- 

 ing the day its body is solid red, but when active in 

 the water column after dark, its lower sides are 

 silvery, affording countershading like that de- 

 scribed for nocturnally active M. leiognathus in 

 the Gulf of California (Hobson, 1968a). This noc- 

 turnal pattern was illustrated earlier (Hobson, 

 1972: Figure 6). 



Thirty-nine specimens (120: 74-145 mm) were 

 speared at different times of the day and night. All 

 20 that were collected either over the reef at night 

 (later than 4 h after sunset), or from shelter sites 

 within an hour of sunrise, had their guts full of 

 food. In contrast, 13 of 14 collected from shelter 

 sites during the afternoon and evening twilight 

 had empty guts (3 had a few fragments posteriorly 

 in their intestines), and the 14th had in its 

 stomach only well-digested fragments. Of the re- 

 maining five, collected above the reef early during 

 the night (within 1 h after last light), four had 

 their guts completely empty, indicating they had 

 not as yet hunted successfully at that early hour, 

 but the fifth was full of fresh calanoid copepods of a 

 species that was exceptionally numerous around 

 our diving lights for about 45 min shortly after 

 last light on that particular evening. Items in the 

 22 individuals that contained identifiable mate- 

 rial are listed in Table 16. 



CONCLUSION.— Myripris^is kuntee is a 



nocturnal planktivore that takes mostly crab 

 megalops and other Crustacea. 



Mijripristis murdjan (Forskal) 



This holocentrid is numerous in Kona, where 

 during the day it aggregates in reef crevices and 

 under coral overhangs, especially where there is 

 shelter from prevailing seas (Figure 14). The 

 twilight activity of this species has been described 

 (Hobson, 1972, as M. berndti). About 30 min after 

 sunset it emerges from its daytime shelter and 

 aggregates in the water column above the reef, 

 generally rising to levels higher than those at- 

 tained by M. kuntee (see above). Immedi- 

 ately, there is a general movement offshore. 

 It remains uncertain how far it swims offshore 

 — perhaps it does not go much beyond the drop-off 

 into deep water, which is a major feeding ground 

 for diurnal planktivores (Hobson, 1972). The 

 offshore move is obscured by the circumstance 

 that at any given time during the night many 

 individuals of this species are swimming over the 

 inshore reefs. Nevertheless, there are consistently 

 fewer of them over inshore reefs on dark nights 

 than on moonlit nights. Gosline (1965) also noted 

 offshore migrations at night by species of 

 Myripristis in Hawaii. About 40 min before sun- 

 rise this species begins to assemble above its diur- 

 nal shelter, and within 10 min all have taken 

 cover for the coming day. This species shows es- 

 sentially the same day-night difference in color 

 patterns as M. kuntee, above. 



Of 25 individuals (169: 139-270 mm) speared at 

 different times of day and night, all 16 that were 

 taken above the reef at night (later than 4 h after 



Table 16. — Food of Myripristis kuntee. 



939 



