HOBSON: FEEDING RELATIONSHIPS OF FISHES 



Figure 16. — Pterois sphex, a lionfish, swimming close to the reef at night. 



occurs in visible locations on the reef most often 

 after dark — though never far from shelter. 



Fourteen specimens (83: 58-121 mm) were 

 speared during day and night. Of nine that were 

 collected during the afternoon or evening twilight, 

 the guts in six were empty, and three had only 

 well-digested crustacean fragments in their 

 stomachs. On the other hand, all five specimens 

 collected at night (more than 2 h after sunset) con- 

 tained relatively fresh prey in their stomachs. 



All eight specimens that contained food had fed 

 on crustaceans exclusively. Caridean shrimps, 

 which occurred in six, were the major food item 

 (mean percent of diet volume: 56.3; ranking index: 

 42.19). Other food items were: xanthid crabs in 

 three (mean percent of diet volume: 13.8; ranking 

 index: 5.16) and pagurid crabs in one (mean per- 

 cent of diet volume: 0.6; ranking index: 0.08). Five 

 individuals contained unidentified crustacean 

 fragments (mean percent of diet volume: 29.4; 

 ranking index: 18.36). 



CONCLUSION.^J^^erois sphex is a nocturnal 

 predator that takes benthic crustaceans, espe- 

 cially caridean shrimps. 



Scorpaena coniorta (Jenkins) 



Although this small species is the most numer- 

 ous scorpaenid on Kona reefs, the casual observer 

 will encounter it only at night. During the day 

 individuals more than about 50 mm long are deep 

 in reef crevices, whereas many smaller individu- 

 als are motionless among the branches of the coral 

 Pocillopora meandrina (Figure 17). After night- 

 fall, many of these fish occur in exposed positions: 

 the larger individuals are spread widely across 

 the reef, resting immobile on rock or coral, 

 whereas the smaller ones are perched motionless 

 on the sea floor close by the same coral heads that 

 shelter them during the day. However, at any 

 given time of night some of these fish are among 

 the coral branches, just as in daylight. 



Thirty-four specimens (46: 36-67 mm) were col- 

 lected during various times of day and night. Of 

 12 that were taken during afternoon or early eve- 

 ning, most from among coral branches, only 1 had 

 food in its gut (3 had a few fragments posteriorly in 

 their intestine). The one containing food, taken 

 from a coral head, had in its stomach a crab that, 

 based on damage by digestion, probably had been 



945 



