HOBSON: FEEDING RELATIONSHIPS OF FISHES 



Table 20. — Food of Apogon menesemus. 



The diet of A. snyderi, compared with that of A. 

 menesemus, includes a greater proportion of 

 benthic organisms, especially forms from sandy 

 bottom, like hippid crabs. Nevertheless, many of 

 the prey of A. snyderi are free-swimming forms 

 that may or may not have been in the water col- 

 umn when captured. The major item, decapod 

 shrimps, were mostly in their planktonic larval 

 stage. 



CONCLUSION. — Apogon snyderi is a noctur- 

 nal predator that feeds on both free-swimming 

 and benthic forms, mostly crustaceans. 



General Remarks on Cardinalfishes 



Cardinalfishes are widely recognized as being 

 nocturnal. For example, Starck and Davis (1966) 

 reported that all of the apogonids they studied in 

 Florida Keys are nocturnal, and Randall (1967) 

 came to the same conclusion for species in the 

 West Indies; Randall provided food-habit data on 

 two forms, Apogon conklini and A. maculatus, 

 both of which prey primarily on plankton. 



In the Gulf of California, A. retrosella, a rela- 

 tively small nocturnal species (mostly <100 mm 

 long), aggregates above the reef at night, preys on 

 plankton, and its aggregations are more compact 

 under moonlight than on dark nights (Hobson, 

 1965, 1968a). Although the relatively large A. 

 menesemus is solitary when feeding on free- 

 swimming prey above Kona reefs, it remains 

 within about 1 m of the reef, never far from cover. 



Another apogonid occasionally seen in Kona, A. 

 maculiferus, has behavior more like that of A. 

 retrosella in the Gulf of California. Apogon 

 maculiferus is abundant on some Hawaiian reefs 

 and attains a length of about 150 mm (Gosline and 

 Brock, 1960). It was not abundant during this 

 study, however, and all those seen apparently 

 were juveniles that ranged between about 20 and 

 60 mm long. On nights of bright moonlight these 

 small individuals were in aggregations 2 to 3 m 

 above the reef; however, on dark nights they 

 ranged even higher in the water column, their 

 aggregations were more loosely formed, and many 

 of them were solitary. Significantly, limited ob- 

 servations indicate that juveniles of both A. 

 menesemus and A. snyderi ( < 50 mm long) behave 



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