The waters surrounding South Georgia, nestled beneath glaciated mountains, are among the most biologically rich in the Southern Ocean. In February, a team of scientists from the British Antarctic Survey (BAS) and international institutions embarked on an important research expedition to explore the diverse marine life – including groundfish – thriving 300 metres below the surface.
Aboard the Polar Seafish Vessel Sil, the team, led by Chief Scientist Professor Martin Collins, conducted a two-week trawl survey funded by the Government of South Georgia and the South Sandwich Islands (GSGSSI). Their mission: to investigate icefish densities and the distribution of young Patagonian toothfish. This research underpins the sustainably managed fishery in the region.
Professor Martin Collins, a senior marine scientist from BAS, says:
"The groundfish survey, first undertaken in 1988, provides the science that underpins the sustainable management of GSGSSI's mackerel icefish and Patagonian toothfish fisheries. Now, with a 37-year dataset, it has become instrumental in understanding the effect of climate change on the South Georgia marine ecosystem."
The research trawls revealed significant aggregations of mackerel icefish, key to commercial fisheries, as well as abundant South Georgia and Scotia Sea icefish. These samples are vital for researchers like Huw James, a PhD student at Newcastle University, who will use them to study the life histories and diets of different species.
He says: "Icefish are incredible and unique. We know very little about their spawning behaviour, with some species, like the Scotia Sea icefish, building intricate nests on the seabed. My research will explore their life cycles to better understand population dynamics."
Despite challenging conditions such as 50-knot winds and 4-metre swells, the team completed more trawls and tagged more Patagonian toothfish than in any survey over the past 20 years. Each tagged fish, marked with a unique number below the dorsal fin, will provide critical data on fish movement and growth when recaptured.
For BAS marine and fisheries scientist Kate Owen, these findings are crucial:
"The two- and three-year-old toothfish we observed in this survey will improve our ability to predict future populations and refine models used to set fisheries quotas. We also hope to see some of our 104 tagged fish again one day!"
This year's survey ventured deeper than ever before, thanks to funding from the UK Government's Blue Belt Programme. New explorations into waters between 400 and 750 meters uncovered unique deep-sea species, including dagger-tooth fishes, king crabs, warty squids, and juvenile skates. Some of these rare specimens will be added to the Natural History Museum's collection in London.
For the first time, the survey also trialled a Neuston Net, a specially designed tool to capture larval fish at the water's surface at night. This stage in the life cycle of icefish and toothfish remains poorly understood.
Dr Lorena Romero Martinez, BAS Postdoctoral Fellow and larval fish expert who was involved in the expedition says:
"The successful deployment of the Neuston Net and capture of larval fish is really promising. It allows us to identify different species in South Georgia's surface waters, develop an identification guide for fishery observers, and improve bycatch management in the krill fishery."
The findings from this year's Groundfish survey will be presented at the upcoming meeting of the Commission on the Conservation of Antarctic Marine Living Resources (CCAMLR) in Hobart, Australia. The data collected will play a key role in shaping the sustainable management of South Georgia's fisheries, ensuring the long-term health of these vital marine ecosystems.
