HOBSON: FEEDING RELATIONSHIPS OF FISHES 



because they resemble their surroundings they 

 remain unseen by small prey that swim within 

 striking range (Longley and Hildebrand, 1941; 

 Hiatt and Strasburg, 1960; Starck and Davis, 

 1966; Randall, 1967). This behavior is descriptive 

 of some scorpaenids, but probably is overdrawn as 

 a generalization encompassing the entire family. 

 Such a tactic is adaptive to daylight, and is used by 

 Scorpaenopsis cacopsis in Hawaii (the one fish 

 identified as prey of this predator, a damselfish, is 

 strictly a diurnal species that is not active over the 

 reef at night). Significantly, the fishes that have 

 been reported by other investigators as prey of 

 scorpaenids on tropical reefs similarly imply 

 diurnal predations: blennies (Longley and Hilde- 

 brand, 1941); a wrasse and a parrotfish (Hiatt and 

 Strasburg, 1960); and an angelfish, a surgeonfish, 

 a sardine, a sea horse, and a conger eel (Randall, 

 1967). With perhaps the lone exception of the con- 

 ger eel, these are fishes that swim close to the reef 

 during daylight, and at that time would be vul- 

 nerable to the ambushing tactic of scorpaenids; 

 however, they would not be readily available after 

 dark when most of them rest under cover on the 

 reef or, in the case of the sardine, swim away from 

 the reef. Conspicuously absent among the re- 

 ported prey are the many species of comparable 

 size that are numerous close above the reef at 

 night, including apogonids and holocentrids. One 

 can readily see how camouflage and ambush 

 would be especially suited to daylight, but less 

 significant after dark. Randall (1967), basing his 

 generalization on the West Indian situation, 

 characterized the scorpaenids as diurnal. In 

 Hawaii, most species are predominantly noctur- 

 nal. In addition to Pterois sphex and Scorpaena 

 coniorta, which prey largely on benthic crusta- 

 ceans, as described above, other members of the 

 family that appear on the reef in greater numbers 

 at night include Dendrochirus brachypterus, 

 Scorpaenodes parvipinnis, and Scorpaena bal- 

 lieui. Among feeding scorpaenids, camouflage 

 does not seem to play the important role at night 

 that it does during the day. When these predators 

 are abroad after dark they often contrast mark- 

 edly with their surroundings. Although fishes do 

 not seem to be significant prey at night, the be- 

 havior of these nocturnal scorpaenids indicates 

 that their tactic remains a short lunge from a 

 resting position to capture prey that have inadver- 

 tently come within range. 



Order Perciformes 



Family Serranidae: sea basses 



Sea basses are prominent on most tropical reefs, 

 but the family has no representatives native to 

 shallow Hawaiian reefs (Gosline and Brock, 

 1960). Nevertheless, the widespread Indo-Pacific 

 serranid Cephalopholis argus has been intro- 

 duced into Hawaii from the Society Islands, the 

 first time in 1956, and has since become well es- 

 tablished in Kona. 



Cephalopholis argus Bloch and Schneider 



This solitary fish, numerous on Kona reefs, 

 swims close among overhanging ledges and crev- 

 ices during the day, but is seen less often at night. 

 Because it generally is wary of humans, lack of 

 nocturnal observations could mean that it avoided 

 our diving lights at night. 



Although 6 of 10 specimens (319: 232-520 mm) 

 speared at various times of day were empty, no 

 temporal pattern is recognized, as the 6 were 

 taken from early morning to late afternoon. All 

 four that contained food, also taken at various 

 times during the day (on four different occasions 

 over 3 mo), had fed exclusively on fishes. One, 

 taken during midmorning, contained, because of 

 digestion, what was recognizable only as a fish 

 (125 mm). The other three — one collected during 

 midday, and two late in the afternoon — each con- 

 tained a single moderately digested squirrelfish, 

 Holocentrus xantherythrus (80, 110, and 130 mm, 

 respectively). Holocentrus xantherythrus 

 congregates under ledges during the day in areas 

 where C. argus is active (see the species account 

 for H. xantherythrus above), and thus is available 

 as prey for the sea bass at this time. Cephalopholis 

 argus has been reported to feed on shrimps as well 

 as fishes in the Marshall Islands (Hiatt and Stras- 

 burg, 1960) and on shrimps in the Gilbert Islands 

 (Randall, 1955). In a sample of 98 specimens from 

 Tahiti, Randall and Brock (1960) found that 77.5% 

 contained fishes, whereas 22.5% contained crusta- 

 ceans (shrimps and crabs). 



CONCLUSION. — Cephalopholis argus preys 

 on fishes among reef crevices during the day. Its 

 nocturnal habits remain uncertain. 



General Remarks on Sea Basses 



Diurnal piscivorous habits were reported in 

 Mycteroperca rosacea in the Gulf of California, 



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