HOBSON: FEEDING RELATIONSHIPS OF FISHES 



small fishes that have taken shelter on its ap- 

 proach probably are detected and even driven out 

 from under cover by the exceptionally long barbels 

 of this goatfish. If the probing barbels do in fact 

 drive small fishes from their hiding places, this 

 would account for the behavior of the jacks that 

 follow them, described above. These same prey 

 fishes also shelter themselves at night when they 

 are inactive, so one might ask why this goatfish 

 does not hunt for them at that time too. As re- 

 ported above, P. bifasciatus preys on some of these 

 same fishes (pomacentrids and blennies) when 

 they are inactive under shelter at night. But cap- 

 turing a relatively inert diurnal fish that is rest- 

 ing under cover after dark probably presents dif- 

 ferent problems for a predator than capturing an 

 alert fish that has taken refuge from some specific 

 threat in daylight. It appears that P. bifasciatus is 

 adapted to taking these fishes when they rest 

 under cover at night, whereas P. chryserydros is 

 adapted to take them when they seek shelter in 

 daylight. After dark, P. chryserydros is inactive, 

 resting under reef cover (Figure 24). 



Parupeneus cyclostomus in the Marshall Is- 

 lands, which is closely related to P. chryserydros. 



if not conspecific, was reported by Hiatt and Stras- 

 burg (1960), on the basis of 16 specimens, to be an 

 "active feeder on small benthonic fishes," but may 

 prey more heavily on crustaceans than does the 

 Hawaiian form. 



CONCLUSION. — Parupeneus chryserydros is a 

 diurnal predator that feeds mostly on small fishes. 



General Remarks on Goatfishes 



Despite their supei'ficial similarity, the various 

 goatfishes behave distinctively. Some, such as 

 Mulloidichthys auriflamma and Parupeneus por- 

 phyreus, are primarily nocturnal; others, includ- 

 ing P. chryserydros and P. multifasciatus , are 

 mostly diurnal; and still others, like P. bifasciatus 

 and M. samoensis, regularly hunt prey during 

 both day and night. One might suppose that fishes 

 which probe the sea floor for food would be indif- 

 ferent to changes associated with day and night, 

 but obviously this is not so. Whether a given 

 species of goatfish is primarily diurnal or noctur- 

 nal probably relates to the differential day-night 

 habits of its specific prey. That some goatfishes are 



Figure 24. — -Parupeneus chryserydros, 



a goatfish, resting under a ledge at night, with its exceptionally long chin 

 barbels spread out before it. 



963 



