Spatial structuring in 0-group fish diversity in the Scotia Sea region of the Southern Ocean

The fish community of the Scotia Sea is diverse and plays key roles in Antarctic food webs and biogeochemical cycling. However, knowledge of the spatial and community structure of larval and juvenile fish is limited, particularly in the region surrounding the South Orkney Islands. Here we examine the structure of the 0-group (aged <1 year) fish community using data from a basin-scale survey conducted in early 2019, which sampled the top 200 m of the water column. 347 0-group fish from 19 genera were caught in 58 hauls. A third of all specimens belonged to the genus Notolepis and the nine most common genera comprised over 90% of specimens. Cluster analysis revealed five distinct groupings, the most common were a group dominated by pelagic and shelf slope genera (Notolepis, Muraenolepis and Electrona) found mainly in oceanic waters (depth ≥1000 m), and a group dominated by species with demersal or benthopelagic adults (Chionodraco, Chaenocephalus and Nototheniops) found mainly in shelf waters. Bottom depth was the main environmental determinant of community structure, separating the diverse on-shelf assemblage at the South Orkneys from the less species-rich community of widespread oceanic taxa. Our results indicate the highest diversities of endemic 0-group fish in the upper water column occur on the shelf and near-shelf areas. Dedicated monitoring is recommended to understand the seasonal differences in larval community assemblages and the implications of 0-group fish bycatch within the krill fishery.