Trophic Ecology of Early Developmental Stages of Antarctic Silverfish

Abstract

The Antarctic pelagic ecosystem over the continental shelf is dominated by the Antarctic silverfish Pleuragramma antarctica (Nototheniidae) which represents up to 90% of the fish biomass. P. antarctica is the only notothenioid species to have an entire pelagic life cycle. This species is characterized by a particularly long larval stage that lasts over a year and a vertical distribution with larvae in the surface layer and the older individuals in deeper ones. The reproductive cycle of P. antarctica is closely linked to seasonal sea ice dynamics and early stages depend on the spatial and temporal match with zooplankton production. P. antarctica is planktivorous at all stages of development, larvae are omnivorous actively feeding on diatoms and small copepods such as Oithona and Oncaea spp., while juveniles and adults are strictly carnivorous and feed mainly on copepods and euphausiids. In the early years of its life-history Antarctic silverfish exhibit primarily a marked transition in terms of trophic ecology between larvae and juveniles. The food resource partitioning is relatively clear between larvae and older life stages with a negligible overlap. Although the shift in diet between juveniles and adults remains less obvious in several geographic locations, juveniles and adults seem to share a similar mid-trophic level around Antarctica.