These data are gonad index (gonad mass/total animal mass) and egg size measurements for two Antarctic marine invertebrates, the starfish Odontaster validus and the brittle star Ophionotus victoriae. Data are for samples hand-collected monthly, where weather permits, by scuba divers from sites near the British Antarctic Survey''s research station at Rothera Point, Adelaide Island. Samples were first collected in 1997 and have continued for 19 years to 2015.

Benthic Macrofaunal abundance and biomass data collected during a series of ship-board sampling campaigns in the Barents Sea. As part of the NERC funded Changing Arctic Ocean programme, in July of 2017, 2018 and 2019, the RSS James Clark Ross followed a North-South transect at 30 degrees Longitude. In 2017 six stations were sampled (B3, B13, B14, B15, B16, B17); in 2018 seven stations were sampled (B3, B13, B14, Xs, B15, B16, B17); and in 2019 five stations were sampled (B3, B13, B14, B15, B16). Macrofaunal samples were collected using a USNL corer (surface area 0.1m<sup>2</sup>). On recovery all faunal samples were fixed and preserved with 10% buffered formaldehyde solution. The faunal samples were transported to Plymouth Marine Laboratory where the fauna were extracted, identified to species level where possible using the most up to date literature available, and biomassed (blotted wet weight) to species level. A reference collection has been created containing an example of each taxon to ensure maximum quality control was maintained by the three analysts that conducted the species identification and for subsequent cruise data generated. Funded by the NERC Changing Arctic Ocean Seafloor (ChAOS).

Water column acoustic data collected in the Scotia Sea (from 2016-12-09 to 2017-01-15) during cruise JR16003. 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.

Water column acoustic data collected in the Atlantic Ocean (from 2016-09-26 to 2016-11-03) during cruise JR16001. 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.

This is a mixed data set held in six excel files, containing processed acoustic backscatter data, mesopelagic fish abundance and swimbladder contents from night time sampled RMT25 nets, plus net catch data for all fauna combined and dominant mesopelagic fish in night time RMT25. Acoustic backscatter data is from 6 latitudinal acoustic transects spanning the Scotia Sea, obtained during cruises JR161, JR177, JR200, JR15002 and JR15004 (two transects). Data were collected using a Simrad EK60 echo sounder at 38 kHz. The EK60 was run continuously between Stanley (Falkland Islands) and Signy (South Orkney Islands). Fish data was collected using RMT25 night time net samples from 5 cruises JR161, JR177, JR200, JR15004 and JR16003. The data set focuses on 11 species of mesopelagic fish Bathylagus species, Cyclothone species, Electrona antarctica, Electrona carlsbergi, Gymnoscopelus braueri, Gymnoscopelus fraseri, Gymnoscopelus nicholsi, Krefftichthys anderssoni, Protomyctophum bolini, Protomyctophum tenisoni and Notolepis species. Abundance and proportion data was obtained for combined fish species, and identified by net tow and latitude. Biomass for all fauna and the 11 fish species was calculated from RMT25 night catch log data. Myctophid gas presence absence was determined from a combination of dissection, Computed Tomography and soft tissue X-ray. Funding was provided by the NERC grants NE/L002434/1 and bas010017. This data is embargoed until August 2019.

Water column acoustic data collected in the Scotia Sea (from 2008-04-16 to 2008-04-17) during cruise JR186. 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.

Collection and preservation of open ocean water samples from stations along a transect up the east coastline of Greenland and then across the Fram Strait to Svalbard during May 2018 & August 2019. Two cruises in total to cover annual changes, both on board the James Clark Ross (RRS). A standard CTD cast was deployed to collect the samples, depths were surface and the chlorophyll maximum, selected to support zooplankton net sampling and other on board experiments. Research assistants from SAMS (Scottish Association for Marine Science) were responsible for the sample collection on JR17-005, Dave Pond of Stirling University was responsible for collection on JR18-007. Elaine Mitchell of SAMS was responsible for the sample analysis and data processing. Funding was provided by the DIAPOD - NERC Thematic grant - Changing Arctic Ocean (CAO) programme - NE/P006213/1

Collection and preservation of open ocean water samples from stations along a transect up the east coastline of Greenland and then across the Fram Strait to Svalbard during May 2018. The cruise was to observe spring bloom conditions, on board the RRS James Clark Ross. A standard CTD cast was deployed to collect the samples, depths were surface, the chlorophyll maximum and a deep sample, selected to support zooplankton net sampling and other on-board experiments. Research assistants from SAMS (Scottish Association for Marine Science) were responsible for the sample collection on JR17005, Elaine Mitchell of SAMS was responsible for the sample analysis and data processing. Funding was provided from the DIAPOD - NERC thematic grant - Changing Arctic Ocean programme - NE/P006280/1.

Water column acoustic data collected in the Scotia Sea (from 2009-03-12 to 2009-04-18) during cruise JR200. 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.

Collection and preservation of open ocean water samples from stations along a transect in the Barents Sea over the course of a year from July 2017 - July 2018. Four cruises in total to cover seasonal changes, two on board the James Clark Ross (RRS) and two aboard the Helmer Hansen (RV). A standard CTD cast was deployed to collect the samples, the depths were selected to support Primary Production experiments on board the ship, with deep samples representing 1% PAR. Research assistants from SAMS (Scottish Association for Marine Science) were responsible for the sample collection and Elaine Mitchell of SAMS was responsible for the sample analysis and data processing. This work was funded by Arctic PRIZE - NERC Thematic grant - Changing Arctic Ocean (CAO) programme - NE/P006302/1.