HOBSON: FEEDING RELATIONSHIPS OF FISHES 



on the reef after dark, but even then is mostly 

 exposed only during transit from one crevice to 

 another. 



Seven individuals (169: 73-250 mm) were 

 speared during day and night. Two collected about 

 2 h before daybreak as they swam close among 

 rocks were both full of prey, including fresh mate- 

 rial. Of three others collected in dark caves during 

 midmorning, one was empty and the other two 

 contained only well-digested fragments. Finally, 

 two individuals collected within 1 h after nightfall 

 as they swam in exposed locations among rocks 

 were both empty — apparently having not yet cap- 

 tured prey on their nocturnal foray. The four indi- 

 viduals containing identifiable prey had fed on the 

 items listed in Table 8. 



CONCLUSION.— Brofulo multibarbata is a 

 nocturnal predator that feeds mostly on crusta- 

 ceans and fishes. 



General Remarks on Brotulas 



Hiatt and Strasburg (1960) concluded that 

 Dinematichthys ilucoeteoides in the Marshall Is- 

 lands is very secretive because they never saw a 

 live one, but did not suggest that it might be noc- 

 turnal. They believed that by concealing itself in 

 crevices this brotulid is able to dash out and cap- 

 ture small fishes and crustaceans that unsuspect- 



ingly venture close to its hiding place. Starck and 

 Davis (1966) recognized nocturnal habits in an 

 Atlantic species, Petrotyx sanguineus, which is 

 unseen in daylight, but swims close among reef 

 ledges at night. 



Order Atheriniformes 



Family Atherinidae: silversides 



Pranesus insularum (Jordan and 

 Evermann) — lao 



This silverside is not numerous in Kona, but in 

 daylight small schools of relatively inactive indi- 

 viduals occur at various places along the rocky 

 shore, right at the water's edge. At nightfall these 

 schools disperse, and the members move away 

 from shore, over the reef. They swim high in the 

 water column, just under the water surface, and 

 some of them range out at least as far as the 

 offshore drop-off. 



Using a hard net, 13 individuals (47: 39-70 mm) 

 were collected during both dark nights and moon- 

 lit nights — 9 between 4 and 6 h after sunset and 4 

 during the 2 h before first morning light. Although 

 the gut of 1 was empty, the other 12 were full, 

 including fresh material, as listed in Table 9. 



CONCLUSION. — Pranesus insularum is a noc- 

 turnal planktivore that takes mostly crustaceans 

 and foraminiferans. 



Table 8. — Food of Brotula multibarbata. 



931 



