Diet of Nyctiphanes australis Sars (Crustacea: Euphansiacea)

Abstract

The stomach contents of the euphausiid Nyctiphanes australis were analysed qualitatively on a monthly basis throughout a full year and for each stage of the life cycle. Dietary items occurring in decreasing order of frequency in stomachs were: inorganic matter including sponge spicules; diatoms; dino- flagellates; silicoflagellates; foraminiferans; and crustacean exuviae. Little change in the composition of the main dietary components between life stages was apparent. Minor seasonal changes in stomach contents occurred (i.e. greater prevalence of diatom resting spores and coccoliths during warmer months and greater prevalence of black particulate matter, thought to be zooplankton faecal pellets, in summer). Fluorescence of the full stomachs of adult N. australis was found to be linearly related to carapace length. Filtering rates calculated from this relationship and average levels of chlorophyll a present in south-eastern Tasmanian coastal waters suggest that N. australis could only satisfy about 25% of its carbon requirement from phytoplankton alone. Hence, it is concluded that this euphausiid needs to include detrital and animal matter in its diet.