FEEDING ECOLOGY OF DEEP-WATER LUTJANID SNAPPERS AT PENGUIN BANK, HAWAII

Deepwater snappers are a valuable component of fisheries on slopes and banks in Hawaii and in much of the world's tropics. Their ecology and trophic relationships in these deepwater habitats are poorly known. L ine fishing in this study simultaneously collected six of the seven lu tjanid species that commonly occur in the major deepwater snapper fish ery at Penguin Bank, Hawaii. The catch rate of each species showed die l variability; the patterns of some species were distinctly different. The depth distribution of feeding, as indicated by depth of capture, differed considerably among species; all species were taken within sev eral meters of the bottom. Size (fork length) of the predator species did not appear to be stratified by time of capture (daylight versus da rkness) or median capture depth. Regurgitation of gut contents seemed to be reduced when fish were retrieved at a rate that was slower than used in commercial practice but rapid enough to prevent death or morbi dity while hooked. The food remaining in line-caught specimens appeare d to be representative of what was originally eaten. The six snapper s pecies ate considerable amounts of a wide range of pelagic animals and demersal fishes and much smaller quantities of a few invertebrate ben thic groups. Etelis coruscans, Etelis carbunculus, and Aprion virescen s formed a distinct, primarily piscivorous feeding guild. Pristipomoid es filamentosus and Pristipomoides sieboldii formed a distinct guild d ominated by zooplankton feeding. The few specimens of Pristipomoides z onatus appeared somewhat intermediate in diet. Important planktonic pr ey groups included crustaceans, pteropods, and large, pelagic, colonia l urochordates (e.g., salps). Urochordates made a significant contribu tion to the diet even for some of the primarily piscivorous species. M ajor diel and seasonal shifts in diet were found only in P. filamentos us; they involved the relative proportions of fish, and especially of the major planktonic groups. Our information on diet composition and d epth and time of feeding (catch) suggests that considerable resource p artitioning occurs among these deepwater snappers.