Acoustic backscatter data were collected on board the RRS James Clark Ross during cruise JR19001 on 10/12/2019 in Stromness Harbour and South Georgia. Data were collected using a Simrad EK60 echosounder at 38, 70, 120 and 200 kHz. The EK60 was calibrated on 09/12/2019 in Stromness Harbour, South Georgia. More information about the calibration can be found in the Cruise Report for JR19001. This work was carried in the frame of the Polar Ocean Ecosystem TimeSeries - Western Core Box (POETS-WCB) project.

Acoustic backscatter data were collected on board the RRS James Clark Ross during cruise JR17002 on 20/01/2018 in Bransfield Strait and the caldera of Deception Island. Data were collected using a Simrad EK60 echosounder at 38, 70, 120 and 200 kHz. The EK60 was calibrated on 07/01/2018 in Stromness Harbour, South Georgia. More information about the calibration can be found in the Cruise Report for JR17002. This work was carried in the frame of the Polar Ocean Ecosystem TimeSeries - Western Core Box (POETS-WCB) project.

Acoustic backscatter data were collected on board the RRS Sir David Attenborough during polar science trials 2023 (cruise SD025) on 25/02/2023 in Admiralty Bay, King George Island, Antarctica. Data were collected using a Simrad EK80 echosounder at 18, 38, 70, 120, 200 and 333 kHz. The EK80 was calibrated on 10/03/2023 in the Weddell Sea. This work was supported by NERC core funding to BAS.

Raw (calibrated as per Demer et al., 2015) Simrad EK60 echosounder data (18, 38 and 120 kHz; Kongsberg Maritime, Norway) collected annually in August and September between 2011 and 2016 as part of the Barents Sea Ecosystem Survey (Eriksen et al., 2018) were obtained from the Norwegian Marine Data Centre (Institute of Marine Research, Norway). The data were used to evaluate the StrathE2EPolar (an end-to-end food web model incorporating ice-dependencies to simulate climate-fisheries interactions in the Barents Sea) model. Echosounder data were calibrated and processed (noise removed). Nautical-area-scattering coefficient (NASC, m2 nmi-2: average received echo energy over a given depth range scaled up to a square nautical mile) values were computed between 15 m (maximum vessel draft plus echosounder near-field for all surveys, vessels and frequencies) and 400 m (lower extent of StrathE2EPolar model domain). NASC values at 18 kHz were used as a proxy for fish biomass. NASC values at 120 kHz and where NASC 120 kHz > 38 kHz > 18 kHz were used as a proxy for macro-zooplankton biomass. NASC values were binned into a 0.5 by 0.5-degree grid and averaged to map the spatial distribution of fish and macro-zooplankton. Funded by NERC project Microbes to Megafauna Modelling of Arctic Seas (MiMeMo), NE/R012571/1 (lead), and NE/R012679/1.

Acoustic backscatter data were collected on board the RRS James Clark Ross (cruise JR179) as part of the BIOFLAME-BIOPEARL programme. Data were collected using a Simrad EK60 echo sounder. Data were collected throughout the cruise which ran through the Drake Passage, Bellingshausen Sea and Amundsen Sea in the Southern Ocean, from February to April 2008. The raw data files (Simrad .raw format) are held by the Polar Data Centre (PDC) at the British Antarctic Survey (BAS). *******PLEASE BE ADVISED TO USE PROCESSED DATA******* The JR179 EK60 processed data is now available at https://doi.org/10.5285/ecc51062-1338-445e-bd3c-2e63487d1953.

Acoustic backscatter data were collected on board the RRS James Clark Ross (cruise JR161) as part of the Discovery 2010 programme. Data were collected using a Simrad EK60 echo sounder at 38, 120 and 200 kHz. The EK60 was run continuously from Stanley (Falkland Islands) to Signy (South Orkney Islands), then to South Georgia across the Scotia Sea in the austral spring (October - December) of 2006. Dedicated acoustic transects were also run at eight stations within these transects. The EK60 was calibrated prior to data collection on a previous cruise (JR159 on 13-14th October 2006). More information about the calibration can be found in the Cruise Report for JR159: https://www.bodc.ac.uk/data/information_and_inventories/cruise_inventory/report/jr152_jr159.pdf JR161 was the first of three cruises which comprise the field studies of the British Antarctic Survey''s (BAS) core science Discovery 2010 programme, funded by the Natural Environment Research Council. *******PLEASE BE ADVISED TO USE PROCESSED DATA******* The JR161 EK60 processed data is now available at https://doi.org/10.5285/c831d5e4-8d03-4aea-a6c6-6db101f36d8d.

Acoustic backscatter data were collected on board the RRS James Clark Ross (cruise JR177) as part of the Discovery 2010 programme. Data were collected using a Simrad EK60 echo sounder at 38, 120 and 200 kHz. The EK60 was run continuously from Stanley (Falkland Islands) to Signy (South Orkney Islands), then to South Georgia across the Scotia Sea in the austral summer from December 2007 - February 2008. Dedicated acoustic transects were also run at a number of stations within these transects. The EK60 was calibrated during JR177 (10-11th February 2008). More information about the calibration can be found in the Cruise Report for JR177: https://www.bodc.ac.uk/data/information_and_inventories/cruise_inventory/report/jr177.pdf JR177 was the second of three cruises which comprise the field studies of the British Antarctic Survey''s (BAS) core science Discovery 2010 programme, funded by the Natural Environment Research Council. *******PLEASE BE ADVISED TO USE PROCESSED DATA******* The JR177 EK60 processed data is now available at https://doi.org/10.5285/cfc33544-e1df-4202-9d4b-c99e7f8a51d4.

Acoustic backscatter data were collected on board the RRS James Clark Ross (cruise JR200) as part of the Discovery 2010 programme. Data were collected using a Simrad EK60 echo sounder. This cruise ran two transects (Stanley to Signy and Signy to South Georgia) across the Scotia Sea in the austral autumn (March - April) of 2009. Within these transects, there were a series of stations at which dedicated acoustic transects were run, although the EK60 was run continuously throughout the cruise. JR200 was the third of three cruises which comprise the field studies of the Discovery 2010 programme. The programme was designed to analyse interactions in the Southern Ocean ecosystem. The raw data files (Simrad .raw format) are held by the Polar Data Centre (PDC) at the British Antarctic Survey (BAS). *******PLEASE BE ADVISED TO USE PROCESSED DATA******* The JR200 EK60 processed data is now available at https://doi.org/10.5285/7b86ed5f-0520-4dec-9d1e-f76be05b98c9.

This dataset contains processed acoustic backscatter data that reflect integrated density estimates for Antarctic krill (Euphausia superba). The acoustic backscatter data are from the Western Core Box (WCB), comprising 8 acoustic transects that span the shelf-break at South Georgia. The data were obtained from a time series of 22 cruises carried out between 1996/97 and 2019/20. Data were collected using either a Simrad EK500 or EK60 echo sounder by biological oceanographers working at the British Antarctic Survey under the Ecosystems scientific research programme and predecessor Discovery 2010 and Dynamo research programmes. Funding was provided by the NERC/BAS Antarctic, Logistic, Infrastructure (ALI) Science and predecessor Long Term Monitoring Science research programmes.

Water column acoustic data collected in the Scotia Sea (from 2008-01-01 to 2008-02-17) during cruise JR177. Multi-frequency (38,120 and 200 kHz) acoustic data were collected using a Simrad EK60 echo sounder. The dataset comprises of calibrated and processed 38 kHz volume backscattering strength (Sv, dB re 1m-1). Data processing was undertaken using Echoview and Matlab. Processed netCDF data files are made available as part of the NERC Southern Ocean Network of Acoustics (SONA) and the EU MESOPP project.