HOBSON: FEEDING RELATIONSHIPS OF FISHES 



Table 34. — Food of Chaetodon unimaculatus. 



shallower than 20 m, especially where stony cor- 

 als abound. During the day it generally occurs in 

 pairs, and is active close to the reef, often picking 

 at living corals — both Pontes and Pocillopora. At 

 night it rests close among cover on the reef, alert 

 but apparently inactive. 



Of the 26 specimens (84: 78-94 mm) examined, 

 all 15 that were collected at night (between 4 h 

 after sunset and first morning light) were empty, 

 whereas all 11 that were collected during midday 

 were full of food (including fresh material), as 

 listed in Table 35. 



More so than the other butterflyfishes that feed 

 on stony corals, C. multicinetus does so without 

 also taking fragments of the surrounding skele- 

 ton. 



CONCLUSION. — Chaetodon multicinetus is a 

 diurnal predator that feeds primarily on sclerac- 

 tinian corals (mostly Pontes and Pocillopora) . 



Chaetodon ornatissimiis Solander — 

 ornated butterflyfish 



This butterflyfish is numerous over coral-rich 

 reefs, generally swimming in pairs during the 

 day. It moves from one growth of coral to another, 

 locating and working its mouth over abrasions on 

 the surface of the coral. In this way it feeds on a 



variety of scleractinian corals, including Pontes, 

 Pauona, and Cyphastrea. At night it rests quiet, 

 but alert, close among cover on the reef. Its day- 

 time and nighttime colorations differ strikingly 

 (Figure 29a and b). 



Nineteen specimens (119: 95-140 mm) were 

 examined. All eight that were collected at night, 

 later than 4 h after sunset and before first morning 

 light, had the stomachs and anterior half of the 

 intestines empty. All four that were taken during 

 morning twilight — the earliest 25 min before 

 sunrise — had material in their stomachs, but 

 their intestines were empty (apparently they had 

 just begun to feed). Finally, all seven that were 

 collected during midday were full of food. 



All 11 specimens with material in their 

 stomachs contained only a thick mucus rich in 

 nematocysts, zooxanthellae, and organic debris 

 (mean percent of diet volume and ranking index: 

 99.8). The balance of the gut contents was made up 

 of diatoms and a few algal fragments. 



It is well known that stony corals increase their 

 production of mucus when injured, so this 

 chaetodontid's habit of seeking out abrasions on 

 coral may explain why its gut contents include so 

 much mucus. This species probably obtains 

 significant nourishment from coral mucus, but 

 judging from the numbers of zooxanthellae and 



973 



