in exposed positions on the reef after dark, most 

 are too large to serve as prey for all but the biggest 

 squirrelfishes. 



WATER-COLUMN FEEDERS.— These are the 

 species of Myripristis, all of which are primarily 

 planktivores. This habit is reflected in their 

 sharply upturned mouths, a feature well known as 

 adaptive to feeding on plankton (e.g. Rosenblatt, 

 1967). Based on the food-habit data, crab 

 megalops are the major prey of all three species 

 reported here. 



Earlier (Hobson, 1965, 1968a), I reported that 

 M. leiognathus in the Gulf of California feeds in 

 the water column after dark on planktonic crusta- 

 ceans, including crab larvae. Similarly, Randall 

 (1967) reported that M. jacobus in the tropical 

 Atlantic feeds at night primarily on planktonic 

 organisms, especially crustacean larvae, and Col- 

 lette and Talbot (1972) noted that this species 

 feeds at least 3 m above the reef. Probably similar 

 habits are universal in species of Myripristis. 



FISHERY BULLETIN: VOL. 72, NO. 4 



Order Gasterosteiformes 

 Family Aulostomidae: trumpetfishes 



Aulostonius chinensis (Linnaeus) — niinu 



This distinctive, solitary fish (Figure 15) is 

 numerous on Kona reefs, where it attains the 

 length of at least 700 mm. It exhibits three basic 

 color forms: plain reddish brown, brown with light 

 striping and other marks, and plain yellow. Sev- 

 eral trumpetfish recognized as individuals were 

 seen repeatedly in the same areas throughout the 

 study, and none changed coloration during this 

 time. The habitat of this species is in water deeper 

 than about 5 m close to coral or irregular rocky 

 substrata that offer many ledges and crevices. 



I observed no difference in the behavior of this 

 fish between day and night. At all hours it moves 

 slowly, close to cover, propelling its long, cylindri- 

 cal, rod-straight body mainly by undulating its 

 soft dorsal and anal fins, which are set far back 

 near the tail. The trumpetfish is a stalking pred- 

 ator, and on a few scattered occasions I saw it 



Figure 15. — Aulostomus chinensis, the trumpetfish, a stalking predator. 



942 



