HOBSON: FEEDING RELATIONSHIPS OF FISHES 



Figure 40. — Xanthichthys ringens, a zooplanktivorous triggerfish. In comparison with bottom-feeding triggerfishes, 

 this species has a more upturned mouth that is higher on its head, and its body is more fusiform. Both features are 

 widespread among zooplanktivorous fishes. 



Its shelters, like those of Melichthys niger, above, 

 are small enough so that the fish can wedge itself 

 in by locking its large dorsal spine erect. Each 

 individual fish seems to resort to a specific hole 

 that serves as a refuge by day, and also as a resting 

 place at night when the species is inactive. 



All nine individuals (142: 114-170 mm) speared 

 at various times of the day from among those 

 active close to the reef were full of food, as listed 



in Table 65. Food items were mostly small organ- 

 isms between 1 and 6 mm in their greatest 

 dimension, taken intact; the few exceptions 

 are fragments of about this size from larger or- 

 ganisms. 



Hiatt and Strasburg (1960) found this species 

 numerous on shallow reefs in the Marshall Islands 

 and reported a crustacean and algal diet similar to 

 that of the species in Kona. 



1007 



