FISHERY BULLETIN: VOL. 72, NO. 4 



nocturnal, whereas other are diurnal, is also rec- 

 ognized from other seas. In Florida, Starck and 

 Davis (1966) suspected that Mulloidichthys 

 martinicus feeds at night, whereas they recog- 

 nized diurnal feeding habits in Pseudupeneus 

 maculatus. Longley and Hildebrand (1941), as 

 well as Collette and Talbot (1972), also regarded 

 M. martinicus as nocturnal and P. maculatus as 

 diurnal. Randall (1967) reported that M. mar- 

 tinicus feeds by day as well as night, and described 

 a diet much like that of the two species of 

 Mulloidichthys from Kona. 



Family Kyphosidae: sea chubs 



Kyphosus cinerascens Forskal — nenue 



In Kona, K. cinerascens is most numerous 

 where a basalt reef face confronts the prevailing 

 swell in water deeper than about 8 m. Often over 

 500 mm long, this fish is active throughout the 

 day — usually in groups of up to 10 or more indi- 

 viduals, and often swimming high in the water 

 column. At night, solitary individuals swimming 

 above the sea floor are often encountered in the 

 same areas. 



All three specimens (205: 166-250 mm) col- 

 lected for study had guts full of a wide variety of 

 benthic algae exclusively. Although two of these 

 fish were taken during midday, the other was 

 taken at night, within 1 h before first morning 

 light. No sedimentary material was mixed in 

 these gut contents, indicating that the algae had 

 been bitten, not scraped, off the rocks, or else had 

 been taken as fragments drifting in mid-water. 

 Hiatt and Strasburg (1960) found the same gut 

 contents in specimens from the Marshall Islands. 



CONCLUSION. — Kyphosus cinerascens feeds 

 during the day, cropping algae from rocks or tak- 

 ing them as drifting algal fragments. Its nocturnal 

 habits remain uncertain. 



General Remarks on Sea Chubs 



Sea chubs generally are described as diurnal 

 herbivores (e.g. Longley and Hildebrand, 1941; 

 Starck and Davis, 1966; Randall, 1967). Smith 

 (1907) reported crabs and bivalved mollusks 

 among algae in the diet of Kyphosus sectatrix in 

 the Atlantic Ocean, but these items probably were 

 taken incidentally with the algae. Randall (1967) 

 found only algae and a bit of sea grass in K. secta- 



trix from the West Indies. Starck and Davis (1966) 

 reported that K. incisor rests in sheltered loca- 

 tions on Floridian reefs at night after having fed on 

 drifting sargassum at the water's surface during 

 the day. In the East Indies, however, William N. 

 McFarland, Cornell University (pers. commun.) 

 observed kyphosids active at night. 



Family Chaetodontidae: 

 angelfishes and butterflyfishes 



The chaetodontids comprise two distinct groups: 

 the angelfishes, subfamily Pomacanthinae; and 

 the butterflyfishes, subfamily Chaetodontinae. Of 

 the species treated below, the first two are 

 angelfishes, the remainder are butterflyfishes. 



Holocanthus arcuatus Gray — angelfish 



This angelfish is sparsely distributed on Kona 

 reefs, but being relatively large and distinctive is 

 readily noticed where it occurs. Usually solitary or 

 paired, it swims close among rock ledges and boul- 

 ders at depths below about 8 m. During the day it 

 picks material from the surface of rocks, but was 

 not seen active at night. 



Six specimens ( 136: 123-150 mm) were speared 

 during afternoons, and all had full stomachs. 

 They had fed almost exclusively on sponges (mean 

 percent of diet volume and ranking index: 98.3). 

 The only other items — algae and hydroids — 

 probably were taken incidentally with the 

 sponges. 



CONCLUSION. — Holacanthus arcuatus is a 

 diurnal species that feeds on sponges. 



Centropyge potteri (Jordan and Metz) — 

 potter's angelfish 



An abundant species in coral-rich surround- 

 ings, this small angelfish behaves more like some 

 of the damselfishes than it does other members of 

 its family. A given individual limits its move- 

 ments to restricted, well-defined locations close 

 among fingerlike growths of the coral Porites 

 compressus. During the day it swims about, pick- 

 ing at material growing over dead coral. At night 

 it is alert, but secreted deep among the coral, ap- 

 parently inactive. 



All five specimens (80: 69-86 mm long) speared 

 at various times during the day were full of food. 

 Filamentous algae were the major identifiable 

 item in the gut contents of all five (mean percent of 



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