The UK undertook a bottom trawl survey of CCAMLR sub-Area 48.3 on the FV Sil between the 27thth January and 5th February 2019. A total of 73 random and representative hauls were completed covering depths of between 108 and 352m. Overall biomass of mackerel icefish, Chamsocephalus gunnari, was calculated at 50,897 tonnes with a lower 1-sided 95% interval estimate of 30,288 tonnes. This is lower than in 2017, but is comparable with the long term average. The highest catches were on the moraine banks of the two northern strata and at the western end of Shag Rocks, with one high catch recorded in the South West stratum.
Clear regional differences in C. gunnari diet composition were observed. At Shag Rocks Euphausid spp. made the largest contribution to icefish diet, however the amphipod Themisto sp. dominated the diet around South Georgia. Based on the Index of Relative Importance, the importance of E. superba as a prey species varied across the four regions at South Georgia, ranging from 10.48% IRI in the South West to 33.49% IRI in the South East.
Catches of juvenile Dissostichus eleginoides were small and dominated by fish of 18-26cm (TL) indicating the presence of a cohort of age 1+ fish. Estimated biomass for the other icefish species, Pseudochaenichtys georgianus and Chaenocephalus aceratus, were higher than results obtained in 2017. The estimated biomass of Notothenia rossi was higher than observed in 2017 and is the second highest seen in the survey time series. The estimated biomass of Patogonotothen guntheri was also higher than observed in 2017, and was the third highest in the survey time series.