Winter aspects of the ichthyoplankton community in Antarctic Peninsula waters

摘要

Ichthyoplankton was sampled from the Antarctic Peninsula area of the South Polar Ocean in early winter (May and June 1986). A total of 153 eggs from two species and 1368 larvae or juvenile stages from 12 species were obtained. These included pelagic species, and demersal species with a long pelagic larval or juvenile phase. Most abundant were larvae ofPleuragramma antarcticumandNotothenia kempi, and eggs ofNotothenia neglecta.The distribution of notothenioid and paralepidid larvae was apparently unaffected by ice cover, whereas myctophid larvae were confined to ice-free waters. Areas where newly hatchedChionodraco hamatusoccurred coincided with dense aggregations ofEuphausia superba(Krill) furcilia larvae which is a potential food resource during winter. The hatching of icefish larvae during winter is apparently independent of the seasonal production cycle. Epipelagic eggs ofNotothenia neglectawere found during the spawning season, which suggests that eggs ascend to the surface after demersal spawning and that development takes place near the sea surface during winter. Larvae ofNotothenia kempiwere chiefly confined to shelf and slope waters to the west of the Antarctic Peninsula, with larger larvae found in coastal shelf areas.Pleuragramma antarcticumoccurred in the coastal waters off the Biscoe Islands, in the Gerlache Strait, and in the northern Bransfield Strait. The smallest larvae were found in the northern Bransfield Strait, whereas those at the Biscoe Islands and in Gerlache Strait waters were larger and of a similar size. A cyclonic gyre to the west of the Antarctic Peninsula observed in the austral summer was likely to have affected the larval drift ofPleuragramma antarcticumandNotothenia kempi.Differences in the timing of spawning and hatching and the vertical distribution of these larvae will lead to different transport and spatial distribution patterns. It is hypothesized that early winter conditions do not imply severe limitations on the year-class success of larval fish. Dispersal and increased mortality may occur during the second half of the winter.