scientific article | Trans Am Fish Soc
Haight WR, Parrish JD, Hayes TA
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. Line fishing in this study simultaneously collected six of the seven lutjanid species that commonly occur in the major deepwater snapper fishery at Penguin Bank, Hawaii. The catch rate of each species showed diel 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 several meters of the bottom. Size (fork length) of the predator species did not appear to be stratified by time of capture (daylight versus darkness) 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 morbidity while hooked. The food remaining in line-caught specimens appeared to be representative of what was originally eaten. The six snapper species ate considerable amounts of a wide range of pelagic animals and demersal fishes and much smaller quantities of a few invertebrate benthic groups. Etelis coruscans, Etelis carbunculus, and Aprion virescens formed a distinct, primarily piscivorous feeding guild. Pristipomoides filamentosus and Pristipomoides sieboldii formed a distinct guild dominated by zooplankton feeding. The few specimens of Pristipomoides zonatus appeared somewhat intermediate in diet. Important planktonic prey groups included crustaceans, pteropods, and large, pelagic, colonial urochordates (e.g., salps). Urochordates made a significant contribution to the diet even for some of the primarily piscivorous species. Major diel and seasonal shifts in diet were found only in P. filamentosus; they involved the relative proportions of fish, and especially of the major planktonic groups. Our information on diet composition and depth and time of feeding (catch) suggests that considerable resource partitioning occurs among these deepwater snappers.