Fish functional groups of the North Atlantic and Arctic oceans

International efforts to assess the status of marine ecosystems have been hampered by insufficient observations of food web interactions across many species, their various life stages, and their geographic ranges. Hence, we collated data from multiple databases of fish stomach contents from samples taken across the North Atlantic and Arctic oceans containing 944 129 stomach samples from larvae to adults, with 14 196 unique interactions between 227 predator species and 2158 prey taxa. We use these data to develop a reproducible data-driven approach to classifying broad functional feeding guilds and then apply these to fish survey data from the northeast Atlantic shelf seas to reveal spatial and temporal changes in ecosystem structure and functioning. In doing so, we construct individual predator–prey body-mass scaling models to predict the biomass of prey functional groups, e.g. zooplankton, benthos, and fish, for different predator species. These predictions provide empirical estimates of species- and size-specific feeding traits of fish, such as predator–prey mass ratios, individual prey mass, and the biomass contribution of different prey to predator diets. The functional groupings and feeding traits provided here help to further resolve our understanding of interactions within marine food webs and support the use of trait-based indicators in biodiversity assessments. The data used and predictions generated in this study are published on the Cefas Data Hub at https://doi.org/10.14466/CefasDataHub.149 (Thompson et al., 2024).