Distribution, abundance and ecological relevance of pelagic fishes in the Lazarev Sea, Southern Ocean

Abstract

The distribution and abundance of larval and postlarval fishes was investigated in the Lazarev Sea, Southern Ocean, in March and April 2004. The upper 200 m of the water column were sampled with an 8 m 2 rectangular midwater trawl at 93 stations. The larval species community clus- tered in a diverse coastal community with high densities of Antarctic silverfish Pleuragramma antarcticum larvae and a less diverse offshore community dominated by Antarctic jonasfish Notolepis coatsi and the lanternfish Electrona antarctica. No postlarval fish were caught in coastal areas. The offshore community of postlarval fishes consisted of the deep-sea smelt Bathylagus antarcticus, and the lanternfishes Gymnoscopelus braueri, G. nicholsi and E. antarctica. The latter species clearly dominated, occurring at mean individual and wet mass densities of 0.17 individuals m -2 and 0.26 g m -2 , respectively. A generalized additive model significantly related the density of postlarval E. antarctica to the abundance of Antarctic krill Euphausia superba, ocean depth and sea surface tem- perature. The diet of E. antarctica was dominated by copepods and euphausiid larvae. Mean energy density of E. antarctica in the upper 200 m was 2.8 kJ m -2 , which is equivalent to 36% of the energy stored in Antarctic krill stocks and probably would be considerably higher if a greater depth range were considered. This suggests that E. antarctica is a major energy transmitter in the food web of the Lazarev Sea, challenging the classical krill-dominated food web paradigm of the Southern Ocean.