Biomarker analysis, especially fatty acids (FA) and stable isotopes (SI), has become a useful tool to elucidate the flow of energy and trophic interactions in an ecosystem and to analyse the diet of species that are hard to observe while feeding. Herein we compare FA profiles and SI composition (nitrogen, δ¹⁵N and carbon, δ¹³C) of muscle tissue from two sympatric Antarctic fish species - Notothenia rossii and N. coriiceps – that are key components in the inshore ecosystem of the South Shetland Islands. For both nototheniids, potential food sources from the benthic community (algae, amphipods, polychaetes and gastropods) were screened in order to re-evaluate their trophic position (TP) and the energy flow, taking as representative of the area the local food web of Potter Cove, in King George Island/Isla 25 de Mayo. Significant differences in FA and SI composition between the two fish species (δ¹⁵N / δ¹³C N. rossii: 9.94±0.80‰ / -23.64±1.03‰, N. coriiceps: 11.44±0.42‰ / -21.46±0.46‰) were found. Notothenia rossii showed a higher total FA concentration, with high levels of polyunsaturated FA (PUFA) such as EPA, DHA and ARA. Conversely, the potential food sources tested showed low concentrations of these FAs. This could indicate that both nototheniids are feeding mainly on another food source that was not included in the present study, or that FA bioconversion takes place in these species. While the FA results might suggest a possible trophic niche segregation between N. rossii and N. coriiceps, both species occupy a similar TP (N. rossii = 3.1, N. coriiceps = 3.5). Furthermore, we found a higher total concentration of monounsaturated FA (MUFA) in N. rossii (4348.4 μl/µg) than in N. coriiceps (85.6 μl/µg), which is about 50-fold greater, and is related with a higher buoyancy capacity in N. rossii. In the present study the use of trophic biomarkers did not elucidate which was the main prey item as lipid source for N. rossii and N. coriiceps, suggesting that other food sources need to be analysed and the species fatty acid bioconversion capacity should be further investigated.

An observation on the interaction between marine mammal and krill midwater trawl was carried out onboard the Chinese krill fishing vessel Fu Rong Hai during the 2018/19 fishing season. The underwater and on sea surface observations were both deployed. Although large numbers of Antarctic fur seal Arctocephalus gazella were observed around the vessel during the vessel fishing in the Subarea 48.3, no identified marine mammal was observed in the main body of trawl net. There was no marine mammal by-catch observed either. The observation found the Antarctic fur seals would be attracted by the codend of krill trawl net, especially during the periods difficult to get foods. The observation also indirectly implied that well designed seal escaping devices might reduce the risk of accidently by-catch of Antarctic fur seals. Future researches on the interaction between marine mammals and krill fishing gears would be helpful to understand the relationships between krill fishing and krill predators.

We invite Members to collaborate with the U.S. AMLR Program to conduct a multi-national, empirical study of krill flux through the Bransfield Strait and across the continental shelf surrounding Astrolabe Island. We propose to conduct this study with 20+ acoustically instrumented moorings. Collaboration could include refining study design, deploying and recovering moorings, conducting separate acoustic surveys to estimate krill standing stock within the study area, and, ultimately, data analysis and synthesis.

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.

Reliable species identification and population assessments of skates are crucial for the sustainable management of their vulnerable stocks. However, species identification is a major challenge in skate studies due to convergent morphology within and between genera. In this study, we applied molecular tools to identify specimens of softnose skates (Bathyraja spp.) caught as bycatch from the longline fishery around South Georgia. Mitochondrial DNA Control Region sequence analyses highlighted a discrepancy between previous genetic studies of B. meridionalis and B. maccaini that challenged the identification of our putative B. meridionalis samples. Detailed analyses of Bathyraja data submitted in Genbank lead to the conclusion that our South Georgia samples were likely to be B. meridionalis but further mitochondrial markers are being sequenced to confirm species identity. Genetic diversity of these putative B. meridionalis was low and indicated a single population around South Georgia. We are currently developing faster-evolving microsatellite markers to more robustly assess genetic diversity and population structure in this species.