The dataset contains 3 data files. Firstly, it contains one set of stable isotope compositions expressed as delta13C, d15N, d34S values recovered from fish muscle from a variety of species captured in September 2019 across the Barents Sea as part of the joint IMR-PINRO Barents Sea Ecosystem Survey. Samples were collected by Dr Matthew Cobain and Dr Kim Vane, and isotope data analysed at the university of Southampton. A second dataset contains delta13C and delta18O compositions of fish otolith carbonate recovered from a subset of the same fish. A final sheet contains the full metadata associated with each fish sampled on the survey. All samples were processed by Dr Matthew Cobain or Prof Clive Trueman and stable isotope values determined at the University of Southampton. Funding: Project was funded under the NERC Changing Arctic Ocean project, Coldifsh (NE/R012520/1).

This dataset comprises conventional stomachs contents data for the biomass-dominant species of mesopelagic fish, particularly myctophid fish (Family Myctophidae) in the Scotia Sea. The data were collected by depth-discrete RMT25 net trawls deployed between 0-1000 m between the Antarctic Polar Front and the South Orkney Islands. Samples were collected repeatedly at nominal sampling stations during austral autumn 2004, spring 2006, summer 2008 and autumn 2009 for analyses examining the trophodynamics of Southern Ocean mesopelagic fish and their role in the food web. The data are the quantitative measures of diet composition (prey abundance, frequency and mass) observed from microscope analyses of individual fish stomachs per species.